Affordance-Based Control of Visually Guided Action

The interplay between motor cost and self-efficacy related to walking across terrain in gaze and walking decisions

Motor behaviours, like where to step and which path to walk, rely on gaze shifts to gather visual information necessary to decide the next action. Factors influencing both gaze and walking decisions are poorly understood. Here we had people choose between two paths to determine how a person's belief in their ability to walk across different terrains (i.e., self-efficacy) competed with the expected cost of walking different lengths in deciding how to allocate gaze and the choice of path. When paths differed in both length and terrain, participants directed gaze progressively more to the longer path as self-efficacy about it increased and the difference in rating with the shorter path grew. Participants also chose the higher-rated path more frequently regardless of path length. These results demonstrate that self-efficacy contributes to gaze and walking decisions and suggest that it may play a more dominant role versus energetic cost in both behaviours.

Entropy as a Window Into Behavioral Phase Transitions: Unveiling Contextual Dynamics in Affordance-Based Reaching

Prior work has demonstrated the presence of hysteresis effects in the control of affordance-guided behavior, in that behavioral transitions around a critical action boundary vary with directions of change in said action boundary. To date, research on this topic has overlooked the influence of the global context on these phenomena. We employ an affordance-based reaching task, whereby participants were asked to move a target to a goal by passing through one of two apertures (size variable or size constant). It was found that the direction of change in the size of the variable aperture influenced the point of behavioral transitions, and this effect interacted with the location of a given goal. In addition, we considered fluctuations in the entropy of participants' reach trajectories as a window into the nature of the behavioral phase transitions. Differences in the structure of entropy were found depending on the direction of change in the size variable aperture. These results are discussed in light of a dynamical systems approach, and recommendations for future work are made.

The effect of experience on the perception of affordances for aperture crossing in cycling

To ride successfully and safely, cyclists must perceive and act on the affordances that are available in a given situation. This study investigated whether experience in perceiving and acting with respect to a person-plus-object system would influence whether and how a person choses to cross an aperture of different widths, especially in relation to their maximal action capabilities. We also explore whether the distribution of action modes reflects this effect. We examined the performance (i.e., the probability of successfully crossing the aperture) and the decision (i.e., the probability of attempting to cross the aperture) of 8 experienced cyclists and 16 occasional cyclists in an aperture crossing task. In term of performance, experienced cyclists demonstrated greater ability to cross narrower apertures than occasional cyclists, but there were no such differences when aperture width was scaled to maximal action capabilities. In term of decision, both experienced and occasional cyclists tended to over-estimate their abilities, but the experienced cyclists did so to a greater extent. Our findings indicate that experience improves the ability to perform more complex tasks due to utilizing a wider repertoire of actions, but not necessarily the ability to perceive and actualize (action-scaled) affordances.

Perception of Affordances in Female Volleyball Players: Serving Short versus Serving to the Sideline

Purpose: We investigated youth volleyball players' perception of affordances for different types of serves. Methods: Participants were separated into Less Experienced (n = 13, maximum of 3 years of competitive volleyball experience) and More Experienced (n = 11, minimum of 4 years of competitive volleyball experience) groups. In the Sideline Condition, participants were asked to report the narrowest gap, relative to either the left or right sideline, into which they could serve the ball. In the Short Condition, participants were asked to report the narrowest gap, relative to the net, into which they could serve the ball. Participants then attempted to serve into their reported gaps. Results: The proportion of successful serves was greater for the More Experienced group than for the Less Experienced group, but a statistically significant interaction revealed that this was true only when performing sideline serves. As expected, reported servable gaps were larger for the Short Serve condition (M = 3.66 m, SD = 0.67 m) than for the Sideline Serve condition (M = 1.93 m, SD = 0.71 m), F(1, 22) = 80.45, p < .001, partial η2 = 0.79. Conclusions: Our study extends previous work to a different sport (volleyball) and to different sport-specific actions (serving the ball). The finding that perceived minimum servable gap sizes were larger for short serves than for sideline serves is consistent with differences in the constraints operating on the two types of serves in the context of game play.

Affordance-based control of braking in cycling: Experience reveals differences in the style of control

We investigated whether in an in-situ collision avoidance experiment cyclists regulate braking by adopting an affordance-based control strategy. Within an affordance-based control strategy for braking, deceleration is controlled relative to the maximum achievable deceleration rather than by nulling out deviations from ideal deceleration, and potentially allowing for different braking styles. Twenty active- and eighteen inactive-cyclists were asked to cycle on a straight path in an indoor gym and to stop as close as possible in front of a stationary obstacle. Maximum achievable deceleration was manipulated by loading the bike: no-load, load-5 kg, and load-10 kg. Two approach distances were used to vary cycling speed. Participants in both groups stopped farther from the obstacle when approaching with long- than short-initial distance conditions. No systematic effects of loading on braking performance and control were found across the two groups. However, both groups did increase the magnitude of brake adjustments as ideal deceleration increased and got closer to the action boundary, even when current deceleration approached the ideal deceleration. This indicates that participants adopted an affordance-based control strategy for braking. Two braking styles were identified: an aggressive style, characterized by a late braking onset and a high, steep peak in ideal deceleration, and a conservative style, characterized by an early braking onset and gradual, linear increase in ideal deceleration. The aggressive braking style was more prevalent among the active-cyclists. We suggest that the braking styles emerge from differences in calibration between information and action. The novelty of our work lies in confirming that cyclists adopt an affordance-based control strategy in an in-situ experiment and in demonstrating and explicating how affordance-based control can incorporate the emergence of different styles of braking.

An ecological and embodied approach for training the racecar driver

In the dynamic sport of racecar driving, split-second decisions and rapid execution are imperative. Such an environment requires a tight functional coupling of perception and action. This paper introduces an approach for training racecar drivers rooted in ecological and embodied perspectives. It discusses three pivotal affordances of racecar driving: turn-ability, overtake-ability, and defend-ability. The paper also discusses the relevant environment and equipment (i.e., simulators) that can be useful for training racecar drivers. In addition, practice activities relevant for the actual racetrack or to the simulator are discussed. Coaches are encouraged to try and implement the proposed training strategies (or parts of it), evaluating their impact on racing performance. Furthermore, researchers can continue exploring these principles, fostering a fusion of empirical insights with practical expertise from coaches and racing communities. By synergizing empirical research with insights from practitioners, we can refine the strategies employed in the training of racecar drivers.

Can I catch this ball and do I know if I can? Characterizing the affordance of interceptability for oneself

In this study, we aimed to characterize the affordance of interceptability for oneself using a manual lateral interception paradigm. We asked a two-fold research question: (1) What makes a virtual ball interceptable or not? (2) How reliably can individuals perceive this affordance for oneself? We hypothesized that a spatiotemporal boundary would determine the interceptability of a ball, and that individuals would be able to perceive this boundary and make accurate perceptual judgments regarding their own interceptability. To test our hypotheses, we administered a manual lateral interception task to 15 subjects. They were first trained on the task, which was followed by two experimental sessions: action and judging. In the former, participants were instructed to intercept as many virtual balls as possible using a hand-held slider to control an on-screen paddle. In the latter session, while making interceptions, participants were instructed to call "no" as soon as they perceived a ball to be uninterceptable. Using generalized linear modeling on the data, we found a handful of factors that best characterized the affordance of interceptability. As hypothesized, distance to be covered and ball flight time shaped the boundary between interceptable and uninterceptable balls. Surprisingly, the angle of approach of the ball also co-determined interceptability. Altogether, these variables characterized the actualized interceptability. Secondly, participants accurately perceived their own ability to intercept balls on over 75% of trials, thus supporting our hypothesis on perceived interceptability. Analyses revealed that participants considered this action boundary while making their perceptual judgments. Our results imply that the perceiving and actualizing of interceptability are characterized by a combination of the same set of variables.

Affordances for throwing: An uncontrolled manifold analysis

Movement systems are massively redundant, and there are always multiple movement solutions to any task demand; motor abundance. Movement consequently exhibits 'repetition without repetition', where movement outcomes are preserved but the kinematic details of the movement vary across repetitions. The uncontrolled manifold (UCM) concept is one of several methods that analyses movement variability with respect to task goals, to quantify repetition without repetition and test hypotheses about the control architecture producing a given abundant response to a task demand. However, like all these methods, UCM is under-constrained in how it decomposes a task and performance. In this paper, we propose and test a theoretical framework for constraining UCM analysis, specifically the perception of task-dynamical affordances. Participants threw tennis balls to hit a target set at 5m, 10m or 15m, and we performed UCM analysis on the shoulder-elbow-wrist joint angles with respect to variables derived from an affordance analysis of this task as well as more typical biomechanical variables. The affordance-based UCM analysis performed well, although data also showed thrower dynamics (effectivities) need to be accounted for as well. We discuss how the theoretical framework of affordances and affordance-based control can be connected to motor abundance methods in the future.

A systematic review of perception of affordances for the person-plus-object system

Human behavior often involves the use of an object held by or attached to the body, which modifies the individual's action capabilities. Moreover, most everyday behaviors consist of sets of behaviors that are nested over multiple spatial and temporal scales, which require perceiving and acting on nested affordances for the person-plus-object system. This systematic review investigates how individuals attune to information about affordances involving the person-plus-object system and how they (re)calibrate their actions to relevant information. We analyzed 71 articles-34 on attunement and 37 on (re)calibration with healthy participants-that experimentally investigated the processes involved in the perception of affordances for the person-plus-object system (including attunement, calibration, and recalibration). With respect to attunement, objects attached to the body create a multiplicity of affordances for the person-plus-object system, and individuals learned (1) to detect information about affordances of (and for) the person-plus-object system in a task and (2) to choose whether, when, and how to exploit those affordances to perform that task. Concerning (re)calibration, individuals were able (1) to quickly scale their actions in relation to the (changed) action capabilities of the person-plus-object system and (2) to perceive multiple functionally equivalent ways to exploit the affordances of that system, and these abilities improved with practice. Perceiving affordances for the person-plus-object system involves learning to detect the information about such affordances (attunement) and the scaling of behaviors to such information (calibration). These processes imply a general ability to incorporate an object attached to the body into an integrated person-plus-object system.

The information variables for controlling manual transfer of liquid-filled containers

It is a familiar but challenging task to manually transfer a liquid-filled container without spilling. The action requires stringent control because the dynamics of interacting with the non-rigid aqueous content is complex. In this work, we sought to discover what properties of a liquid-filled container were predictive of transfer without spilling performance. Two candidate variables were tested (Experiment 1): The distance between liquid surface and the container's rim (h) and the container's diameter (d). Participants attempted to transfer 15 containers (3 ds and 5 hs), one at a time and as fast as possible, without spilling. Kinematic analyses showed that the movement's peak velocity and the first peak acceleration were affected by h; the movement time and the frequency of acceleration change were affected by h and d in a hierarchical manner, where transfer without spilling was first affected by h and for full containers, the thick ones were moved more slowly and went through more acceleration change; for not so full containers, the container's diameter did not have any effect. Next, each of the 15 containers was compared with the other 14, and participants judged from a pair of displayed containers which one was more likely to be moved fast without spilling (Experiment 2). Perceived affordance was affected by h and d but not by whether containers were placed upright or tilted. In general, thinner and less full containers were judged as easier to be moved fast without spilling.

Sunglass tint does not impact the indoor catching performance of cricket fielders

Introduction

Sunglasses are worn by outdoor athletes such as cricketers for many reasons, including comfort and glare reduction, which may help to improve vision. Anecdotally they are purported to have performance-enhancing benefits, but there is a lack of evidence for this. Further, it appears that fielders are the only position in cricket who wear sunglasses. Therefore, this study aimed to compare the catching performance of fielders when wearing three different colour sunglasses tints during an indoor, laboratory-based experiment.

Methods

Twenty-one male cricketers currently playing for a university or amateur provincial teams in Makhanda, South Africa, who were non-habitual sunglass wearers, were recruited for this study. An optometrist administered pre-screening tests. Players had four testing sessions during which they wore a different colour tint at each session indoors (clear, blue, G30 (rose), and red). Players were required to catch 18 balls projected from a bowling machine. The number of balls caught, as well as the quality of the catch, was recorded. At the final session, they were asked which tint they thought was best.

Results

Pre-screening tests showed that the red lens was best for contrast sensitivity and stereopsis. During data collection, sunglass tint did not affect catching performance. The players perceived the red lens as the worst and the G30 as the best.

Discussion

It can be concluded that catching performance indoors is not affected by tint colour.

Generalizing the optic flow equalization control law to an asymmetrical person-plus-object system

Visually guided action in humans occurs in part through the use of control laws, which are dynamical equations in which optical information modulates an actor's interaction with their environment. For example, humans locomote through the center of a corridor by equalizing the speed of optic flow across their left and right fields of view. This optic flow equalization control law relies on a crucial assumption: that the shape of the body relative to the eyes is laterally symmetrical. Humans engaging in tool use are often producing person-plus-object systems that are not laterally symmetrical, such as when they hold a tool, bag, or briefcase in one hand, or when they drive a vehicle. This experiment tests a new generalized control law for centered steering that accounts for asymmetries produced by external tool use. Participants held an asymmetrical bar and centered themselves within a virtual moving hallway while the speed of the virtual walls were systematically changed. The results demonstrate that humans engaging with an asymmetrical tool can (1) perceive the asymmetry of a person-plus-object system, (2) use that information to modulate the use of optic flow equalization control laws for centered steering, and (3) functionally incorporate the asymmetrical tool into their perception-action system to successfully navigate their environment.

Performance variability and affordance perception: practice effects on perceptual judgments for walking versus throwing

To judge whether an action is possible, people must perceive "affordances"-the fit between features of the environment and aspects of their own bodies and motor skills that make the action possible or not. But for some actions, performance is inherently variable. That is, people cannot consistently perform the same action under the same environmental conditions with the same level of success. Decades of research show that practice performing an action improves perception of affordances. However, prior work did not address whether practice with more versus less variable actions is equally effective at improving perceptual judgments. Thirty adults judged affordances for walking versus throwing a beanbag through narrow doorways before and after 75 practice trials walking and throwing beanbags through doorways of different widths. We fit a "success" function through each participant's practice data in each task and calculated performance variability as the slope of the function. Performance for throwing was uniformly more variable than for walking. Accordingly, absolute judgment error was larger for throwing than walking at both pretest and posttest. However, absolute error reduced proportionally in both tasks with practice, suggesting that practice improves perceptual judgments equally well for more and less variable actions. Moreover, individual differences in variability in performance were unrelated to absolute, constant, and variable error in perceptual judgments. Overall, results indicate that practice is beneficial for calibrating perceptual judgments, even when practice provides mixed feedback about success under the same environmental conditions.

The effectiveness of penalty takers' deception: A scoping review

Attackers are supposed to take advantage of producing deceptive actions in competitive ball sports, particularly in penalty situations. We conducted a scoping review of the experimental literature to scrutinize whether penalty takers do indeed benefit from using deceptive actions in penalty situations, especially by increasing the likelihood to score a goal. Studies using video-based and in-situ tasks in which soccer and handball goalkeepers try to save a penalty were evaluated. Results showed that penalty takers' manipulation of spatial information available to the goalkeeper during deception (i.e., by using misleading and/or disguising actions) is less effective in in-situ than video-based studies. We argue that this difference occurs because goalkeepers adapt differently to the spatiotemporal constraints in the video-based and in-situ tasks. Goalkeepers appear to prioritize picking up spatial information in video-based tasks while prioritizing temporal information in-situ tasks. Therefore, the manipulation of spatial information appears to be less effective in the more representative in-situ studies than in video-based studies. In order to deceive, penalty takers are advised to manipulate temporal information during on-field penalty situations.

The visual control of locomotion when stepping onto moving surfaces: A comparison of younger and older adults

Stepping between static and moving surfaces presents a locomotor challenge associated with increased injury frequency and severity in older adults. The current study evaluates younger and older adults' behaviours when overcoming challenges sampling moving walkway and escalator environments. Twelve younger adults (18-40 years, Male = 8) and 15 older adults (60-81 years, Male = 5) were examined using an integration of optoelectronic motion capture and mobile eye-tracking. Participants were investigated approaching and stepping onto a flat conveyor belt (static or moving; with or without surface (demarcation) lines). Specifically, the four conditions were: (i) static surface without demarcation lines; (ii) static surface with demarcation lines; (iii) moving surface without demarcation lines; and (iv) moving surface with demarcation lines. A two (age group) x two (surface-condition) x two (demarcation-condition) linear mixed-model revealed no main or interaction effects (p > .05) for perturbation magnitude, indicating participants maintained successful locomotion. However, different adaptive behaviours were identified between conditions with moving and accuracy demands (e.g., moving surfaces increased step length, demarcations reduced step length). Between subject effects identified differences between age groups. Older adults utilised different behaviours, such as earlier gaze transfer from the final approach walkway step location. Overall, the current study suggests that adaptive behaviours emerge relative to the environment's specific demands and the individual's action capabilities.

Can I Squeeze Through? Effects of Self-Avatars and Calibration in a Person-Plus-Virtual-Object System on Perceived Lateral Passability in VR

With the popularity of Virtual Reality (VR) on the rise, creators from a variety of fields are building increasingly complex experiences that allow users to express themselves more naturally. Self-avatars and object interaction in virtual worlds are at the heart of these experiences. However, these give rise to several perception based challenges that have been the focus of research in recent years. One area that garners most interest is understanding the effects of self-avatars and object interaction on action capabilities or affordances in VR. Affordances have been shown to be influenced by the anthropometric and anthropomorphic properties of the self-avatar embodied. However, self-avatars cannot fully represent real world interaction and fail to provide information about the dynamic properties of surfaces in the environment. For example, pressing against a board to feel its rigidity. This lack of accurate dynamic information can be further amplified when interacting with virtual handheld objects as the weight and inertial feedback associated with them is often mismatched. To investigate this phenomenon, we looked at how the absence of dynamic surface properties affect lateral passability judgments when carrying virtual handheld objects in the presence or absence of gender matched body-scaled self-avatars. Results suggest that participants can calibrate to the missing dynamic information in the presence of self-avatars to make lateral passability judgments, but rely on their internal body schema of a compressed physical body depth in the absence of self-avatars.

Perceptual-motor recalibration is intact in older adults

From an ecological perspective, perceptual-motor recalibration should be a robust and adaptable process, but there are suggestions that older adults may recalibrate slower. Therefore, this study investigated the age-related temporal effects in perceptual-motor recalibration after motor disturbances. In three experiments, we disturbed young and older adults' perception-action by fitting weights around their ankles and asking them to climb stairs or cross obstacles repeatedly. In Experiment 1, participants (n = 26) climbed stairs with different ankle weights. An innovative methodology was applied, identifying the timeline of recalibration as the point where a stable movement pattern emerged. Experiment 1 showed that older adults recalibrated slower than young adults in lighter (but not heavier) weight conditions. In Experiment 2, participants (n = 24) crossed obstacles with different ankle weights. Results showed that older adults recalibrated faster than young adults. Finally, in Experiment 3, participants (n = 24) crossed obstacles of unpredictable and varying heights with heavy ankle weights. Again, results showed that older adults recalibrated faster than young adults. Taken together these results show that although older adults had reduced muscle strength and flexibility, they recalibrated quickly, especially when the task was more challenging.

An embodied and ecological approach to skill acquisition in racecar driving

Racecar driving is a fast-paced sport that presents the driver-athlete with many perception-action coupling and decision-making challenges. One question that arises is how racecar drivers deal with the influx of perceptual information and manage to perform successfully in such high speeds and, as a result, very limited time to make decisions and act upon them. In this perspective paper, I suggest that the ecological approach is one theoretical framework that can help researchers understand how skill is acquired in racecar driving. I also suggest that an embodied perception of affordances can provide a good basis for research in the field. Specifically, it is an extended embodied cognition that includes not only the driver's mind and body, but the car itself. In a sense, the driver and the car are embodied into one unit and any perception of affordances should be based on this unit. This paper will also discuss the constraints during a race, the affordances the race driver must perceive and how they change over the course of a race, and how researchers can use a racecar driving paradigm to study human perception and action from an embodied and an ecological approach. Specifically, because the driver is seated, measuring EEG and eye movements is relatively simple and can provide additional information on drivers' visual perception of affordances, and their ability to act upon them.

Did I Hit the Door? Effects of Self-Avatars and Calibration in a Person-Plus-Virtual-Object System on Perceived Frontal Passability in VR

The availability of new and improved display, tracking and input devices for Virtual Reality experiences has facilitated the use of partial and full body self-avatars in interaction with virtual objects in the environment. However, scaling the avatar to match the user's body dimensions remains to be a cumbersome process. Moreover, the effect of body-scaled self-avatars on size perception of virtual handheld objects and related action capabilities has been relatively unexplored. To this end, we present an empirical evaluation investigating the effect of the presence or absence of body-scaled self-avatars and visuo-motor calibration on frontal passability affordance judgments when interacting with virtual handheld objects. The self-avatar's dimensions were scaled to match the participant's eyeheight, arms length, shoulder width and body depth along the mid section. The results indicate that the presence of body-scaled self-avatars produce more realistic judgments of passability and aid the calibration process when interacting with virtual objects. Also, participants rely on the visual size of virtual objects to make judgments even though the kinesthetic and proprioceptive feedback of the object is missing or mismatched.

Visual occlusion effects on youth football players’ performance during small-sided games

This study aimed to explore how youth players’ physical, technical and positional performance may be affected by visual occlusion when playing under different SSG pitch sizes. Under-15 players performed two experimental scenarios: a) normal situation, without visual occlusion; b) visual occlusion, by using an eye patch in the eye corresponding to the dominant foot. These scenarios were tested in a small (40x30m) and a larger pitch (50x35m). Players’ positional data was used to compute tactical and time-motion variables. In addition, technical analysis was comprised using video footage. Playing with visual occlusion in the larger pitch size induced higher distance covered while walking but lower running distance (p < .05). Although no statistically significant effects were identified between the normal and visual occlusion conditions for the tactical behaviour and technical performance a lower number of successful passes (small to moderate effect sizes) and higher regularity in the distance to the opponent’s team centroid (moderate effect size) were found with visual occlusion. Players covered more distance and achieved higher maximum speed in the larger compared to the small pitch (moderate to large effect size, p < .05), while also increasing their distance to both team’s centroid and increasing the regularity to these distances (moderate to large effect size, p < .05). Overall, despite similar effects for tactical and technical variables, some important practical information can be depicted. Accordingly, coaches may use the visual occlusion to promote more stable and regular behaviors while decreasing the physical demands. Larger pitches may be used to increase the distance between players’ and teams, as well as to induce higher physical load in both the normal and visual occlusion conditions. From the technical perspective, coaches may design smaller pitches to emphasize the use of the non-dominant foot during the occlusion scenario and promote the pass during the normal scenario.

The Ecological Dynamics Framework: An Innovative Approach to Performance in Extreme Environments: A Narrative Review

(1) Background: Uncertainty in extreme sports performance environments, such as climbing, provides considerable psycho-emotional and physiological demands, notably due to the many different environments in which climbing can be performed. This variety of environments, conditions of practice and engagement would challenge the acquisition of perceptual-motor skills; (2) Methods: To better understand how perceptual-motor skills are controlled and acquired in climbing, we proposed a narrative review anchored in the ecological dynamics theoretical framework and showed how this theoretical framework would support a nonlinear pedagogy to skill acquisition and to design safe learning and training situations that are representative of extreme performance contexts; (3) Results: We explained three theoretical pillars and we provide examples for design intervention following nonlinear pedagogy, notably (i) to set a constraint-led approach (in particular task constraint), (ii) to implement conditions of practice (constant vs. variable, imposed vs. self-controlled), (iii) to promote adaptive and creative behavioral variability during practice; (4) Conclusions: The challenge for the extreme sport practitioner is how to set up conditions of practice for efficient exploration in a manner that manages the dangers of performing in uncertain environments. Representing uncertainty within the relative safety of indoor settings may be one approach for preparing climbers for performance in extreme environments.

On the psychological origins of tool use

The ubiquity of tool use in human life has generated multiple lines of scientific and philosophical investigation to understand the development and expression of humans' engagement with tools and its relation to other dimensions of human experience. However, existing literature on tool use faces several epistemological challenges in which the same set of questions generate many different answers. At least four critical questions can be identified, which are intimately intertwined-(1) What constitutes tool use? (2) What psychological processes underlie tool use in humans and nonhuman animals? (3) Which of these psychological processes are exclusive to tool use? (4) Which psychological processes involved in tool use are exclusive to Homo sapiens? To help advance a multidisciplinary scientific understanding of tool use, six author groups representing different academic disciplines (e.g., anthropology, psychology, neuroscience) and different theoretical perspectives respond to each of these questions, and then point to the direction of future work on tool use. We find that while there are marked differences among the responses of the respective author groups to each question, there is a surprising degree of agreement about many essential concepts and questions. We believe that this interdisciplinary and intertheoretical discussion will foster a more comprehensive understanding of tool use than any one of these perspectives (or any one of these author groups) would (or could) on their own.

Time for Space and the Stability of Prospective Control: Reaching-to-Grasp Gibson

Gibson formulated an approach to goal-directed behavior using prospective information in the context of visually guided locomotion and manual behavior. The former was Gibson's paradigm case, but it is the rapidity of targeted reaching that has provided the special challenge for stable control. Recent treatments of visually guided reaching assume that internal forward models are required to generate stable behavior given delays caused by neural transmission times. Internal models are representations of the sort eschewed by Gibson in favor of prospective information. Reaching is usually described as guided using relative distances of hand and target, but prospective information is usually temporal rather than spatial. We describe proportional rate control models that incorporate time dimensioned prospective information and show they remain stable in the face of delays. The use of time-dimensioned prospective information removes the need for internal models for stable behavior despite neural transmission delays and allows Gibson's approach to prevail.

Social media enabled interactions in healthcare: Towards a taxonomy

Healthcare users and providers increasingly utilize social media to interact with one another. For a future understanding of when and how these interactions supplement or replace offline doctor-patient interactions, it is essential to understand who interacts, about what, and how these interactions can be categorized in a taxonomy. We draw on affordance theory and employ a mixed-methods approach to study social media interactions among healthcare users and providers. We first engage in qualitative content analysis, which is followed by cluster analysis. We identify five archetypal interactions and categorize these in a taxonomy that adds to current literature on how social media is utilized in the healthcare context. We also provide a clear and systematic overview of the interactions in different social media categories that can stimulate future research regarding doctor-patient interactions. Furthermore, we identify a new and distinct type of social media enabled interaction in healthcare, namely lifestyle support, focusing on prevention.

Ecological Values Theory: Beyond Conformity, Goal-Seeking, and Rule-Following in Action and Interaction

Values have long been considered important for psychology but are frequently characterized as beliefs, goals, rules, or norms. Ecological values theory locates them, not in people or in objects, but in ecosystem relationships and the demands those relationships place on fields of action within the system. To test the worth of this approach, we consider skilled coordination tasks in social psychology (e.g., negotiating disagreements, synchrony and asynchrony in interactions, and selectivity in social learning) and perception-action (e.g., driving vehicles and carrying a child). Evidence suggests that a diverse array of values (e.g., truth, social solidarity, justice, flexibility, safety, and comfort) work in a cooperative tension to guide actions. Values emerge as critical constraints on action that differ from goals, rules, and natural laws, and yet provide the larger context in which they can function effectively. Prospects and challenges for understanding values and their role in action, including theoretical and methodological issues, are considered.

Gravity and Known Size Calibrate Visual Information to Time Parabolic Trajectories

Catching a ball in a parabolic flight is a complex task in which the time and area of interception are strongly coupled, making interception possible for a short period. Although this makes the estimation of time-to-contact (TTC) from visual information in parabolic trajectories very useful, previous attempts to explain our precision in interceptive tasks circumvent the need to estimate TTC to guide our action. Obtaining TTC from optical variables alone in parabolic trajectories would imply very complex transformations from 2D retinal images to a 3D layout. We propose based on previous work and show by using simulations that exploiting prior distributions of gravity and known physical size makes these transformations much simpler, enabling predictive capacities from minimal early visual information. Optical information is inherently ambiguous, and therefore, it is necessary to explain how these prior distributions generate predictions. Here is where the role of prior information comes into play: it could help to interpret and calibrate visual information to yield meaningful predictions of the remaining TTC. The objective of this work is: (1) to describe the primary sources of information available to the observer in parabolic trajectories; (2) unveil how prior information can be used to disambiguate the sources of visual information within a Bayesian encoding-decoding framework; (3) show that such predictions might be robust against complex dynamic environments; and (4) indicate future lines of research to scrutinize the role of prior knowledge calibrating visual information and prediction for action control.

The Effect of Navigation Demand on Decision Making in a Dynamic, Sport-Inspired Virtual Environment

Athletes commonly make decisions about the passability of closing gaps when navigating sport environments. This study examined whether increased temporal pressure to arrive at a desired location modifies these decisions. Thirty participants navigated toward a waypoint in a virtual, sport-inspired environment. To do so, they had to decide whether they could pass through closing gaps of virtual humans (and take the shortest route) or steer around them (and take a longer route). The decision boundary of participants who were time pressured to arrive at a waypoint was biased toward end gaps of smaller sizes and was less reliably defined, resulting in a higher number of collisions. Effects of temporal pressure were minimized with experience in the experimental task. Results indicate that temporal pressure affects perceptual-motor processes supporting information pickup and shapes the information-action coupling that drives compliance with navigation demands. Theoretical and practical implications are discussed.

The influence of skill and task complexity on perception of nested affordances

This study investigated how skill level and task complexity influence the calibration of perception–action and particularly how close an individual acts relative to his or her maximal action capabilities. Complexity was manipulated between two (Touch, Grasp) and more than two (Removing, Moving Up) nested affordance conditions. For all conditions, we examined whether advanced climbers had greater maximal action capabilities than intermediate climbers or whether they better scaled their action (i.e., acted nearer to their maximal action capabilities) or both. Eleven intermediate and 11 advanced male climbers were first asked to estimate the maximum distance that they could reach a climbing hold. The hold was moved along a slide and fixed once requested by the participant; subsequently, the distance to the starting hold was measured. After each estimation, the participant was required to execute the climbing action. After four estimation-action trials in each of the four conditions, the maximal action capability (i.e., actual maximal reaching distance) was determined. Advanced climbers demonstrated greater actual maximal reaching distances than intermediate climbers for all conditions, but they only estimated greater maximal reaching distances for the more complex conditions, which featured more than two nested affordances. When estimated maximal reaching distances were scaled to actual maximal reaching distances, advanced climbers did not differ from intermediate climbers for any condition, and there were no differences between conditions. Our findings indicate that expertise was a function of greater action capabilities, but not due to the accuracy of calibration.

Exploring to learn and learning to explore

In respect to ecological psychology processes of attunement and calibration, this critical review focusses on how exploratory behaviors may contribute to skilled perception and action, with particular attention to sport. Based on the theoretical insights of Gibson (The senses considered as perceptual systems, Houghton Mifflin, Boston, 1966) and Reed (Encountering the world: Toward an ecological psychology, Oxford University Press, New York, 1996), exploratory and performatory actions have been differentiated in numerous experiments to study the perception of opportunities of action. The distinction between exploratory and performatory actions has informed the study of infant behavior in developmental psychology. In the current article, we highlight limitations with this distinction in the study of sports performers. We propose that a dynamic view of exploratory behavior would reveal how individuals develop exploratory activity that generates information about the fit between environmental properties and action capabilities. In this aim, practitioners should: (1) give learners the opportunity to safely develop exploratory behaviors even when they act outside their action boundary; and (2) guide learners to search for more reliable information to develop exploratory behaviors that would enhance the transfer of skills to various performance contexts.

Psychology in an Indeterminate World

By sharing their world, humans and other animals sustain each other. Their world gets determined over time as generations of animals act in it. Current approaches to psychological science, by contrast, start from the assumption that the world is already determined before an animal's activity. These approaches seem more concerned with uncertainty about the world than with the practical indeterminacies of the world humans and nonhuman animals experience. As human activity is making life increasingly hard for other animals, this preoccupation becomes difficult to accept. This article introduces an ecological approach to psychology to develop a view that centralizes the indeterminacies of a shared world. Specifically, it develops an open-ended notion of "affordances," the possibilities for action offered by the environment. Affordances are processes in which (a) the material world invites individual animals to participate, while (b) participation concurrently continues the material world in a particular way. From this point of view, species codetermine the world together. Several empirical and methodological implications of this view on affordances are explored. The article ends with an explanation of how an ecological perspective brings responsibility for the shared world to the heart of psychological science.

Learning and transfer of perceptual-motor skill: Relationship with gaze and behavioral exploration

Visual and haptic exploration were shown to be central modes of exploration in the development of locomotion. However, it is unclear how learning affects these modes of exploration in locomotor task such as climbing. The first aim of this study was to investigate the modifications of learners' exploratory activity during the acquisition of a perceptual-motor skill. The second aim was to determine to what extent the acquired perceptual-motor skill and the learners' exploratory activity were transferred to environments presenting novel properties. Seven participants attended 10 learning sessions on wall climbing. The effects of practice were assessed during pretest, posttest, and retention tests, each composed of four climbing routes: the route climbed during the learning sessions and three transfer routes. The transfer routes were designed by manipulating either the distance between handholds, the orientation of the handholds or the handholds shape. The results showed that the number of exploratory hand movements and fixations decreased with practice on the learning route. A visual entropy measure suggested that the gaze path in this route became more goal-directed on posttest, but some search was necessary on the retention test. The number of exploratory movements also decreased on the three transfer routes following practice, whereas the number of fixations was higher than on the learning route, suggesting that, with learning, participants relied more on exploration from a distance to adapt to the new properties of the transfer routes. Analyses of the individual performances and behaviors showed differences in the development of skilled exploratory activity.

Developmental differences across the lifespan in the use of perceptual information to guide action-based decisions

Perceptual information about unfolding events is important for guiding decisions about when and how to move in real-world action situations. As an exemplary case, road-crossing is a perceptual-motor task where age has been shown to be a strong predictor of risk due to errors in action-based decisions. The present study investigated age differences between three age groups (Children: 10-12 years old; Adults: 19-39 years old; Older Adults: 65 + year olds) in the use of perceptual information for selection, timing, and control of action when crossing a two-way street in an immersive, interactive virtual reality environment. Adults and children selected gaps to cross that were consistent with the use of a time-based information variable (tau), whereas older adults tuned less into the time-based variable (tau) to guide road-crossing decisions. For action initiation and control, children and adults also showed a strong ability to precisely time their entry with respect to the lead vehicle maximising the available time to cross and coordinating walking movements with the tail vehicle to ensure they were not on a collision course. In contrast, older adults delayed action initiation and showed difficulty coordinating self-movement with the approaching vehicle. This study and its results tie together age-based differences in the three components of action decision-making (selection, timing and control) within a unified framework based on perceptual information. The implications of these age-related differences in action decisions and crossing behaviours are discussed in the context of road safety.

Goalkeeping in the soccer penalty kick: The dive is coordinated to the kicker's non-kicking leg placement, irrespective of time constraints

Traditionally, goalkeeping in the soccer penalty kick has been studied using video-based technology, in which goalkeepers watched video footage of penalty kicks and indicated perceived ball direction. By omitting the requirement to actually dive or jump to the ball, these studies overlooked how action capabilities constrain goalkeepers' actions. By contrast, we examined whether goalkeeping in the penalty kick is consistent with affordance-based control, that is, whether goalkeepers guide their dive by taking into account their action capabilities (i.e., the time they need to intercept the ball). To this end, high- and moderate-skilled goalkeepers faced in-situ penalty kicks. Time constraints were manipulated by varying the kicking distance and the kicker's run-up speed. The results showed that goalkeepers of both skills level scaled the lateral dive onset to their action capabilities, but high-skilled goalkeepers acted closer to their maximum action boundary. In doing so, goalkeepers did not take the varying time constraints into account. Instead, high-skilled goalkeepers acted consistent with a strategy in which they coordinated the onset of the dive with the landing of kicker's non-kicking leg next to the ball. Consequently, we only find partial support for affordance-based control. We propose that this is explained by reliable information becoming available (too) late within the spatiotemporal constraints of the penalty kick.

Control of visually guided braking using constant-[Formula: see text] and proportional rate

This study investigated the optical information and control strategies used in visually guided braking. In such tasks, drivers exhibit two different braking behaviors: impulsive braking and continuously regulated braking. We designed two experiments involving a simulated braking task to investigate these two behaviors. Participants viewed computer displays simulating an approach along a linear path over a textured ground surface toward a set of road signs. The task was to use a joystick as a brake to stop as close as possible to the road signs. Our results showed that participants relied on a weak constant-[Formula: see text] strategy (Bingham 1995) when regulating the brake impulsively. They used discrete [Formula: see text] values as critical values and they regulated the brake so as not to let [Formula: see text] fall below these values. Our results also showed that proportional rate control (Anderson and Bingham 2010, 2011) is used in continuously regulated braking. Participants initiated braking at a certain proportional rate value and controlled braking so as to maintain that value constant during the approach. Proportional rate control is robust because the value can fluctuate within a range to yield good performance. We argue that proportional rate control unifies the information-based approach and affordance-based approach to visually guided braking.

Action capability constrains visuo-motor complexity during planning and performance in on-sight climbing

The capability to adapt to changing conditions is crucial for safe and successful performance in physical activities and sports. According to the affordance‐based control perspective, individuals act in such a way as to take into account the limits of their capability to act. However, it is not clear how strength interacts with skill in shaping performer‐environment interactions. We, therefore, determined whether fingertip strength influences patterns of gaze and climbing behavior on new routes of ever‐increasing difficulty. We expected that comparatively weaker climbers would show less complex behavior because of an inability to perceive and act. Stronger climbers would show more complex visuo‐motor behavior because more opportunities for action remain, even as route difficulty increases. For very strong climbers the route would not be challenging enough, and less complex patterns suffice. Twenty climbers, ranging from lower grade to elite level participated. Maximum fingertip strength was obtained. Participants previewed and then climbed two separate 3 m long traverses, gradually decreasing in edge depth. Gaze and hip positions were collected for subsequent computation of gaze transition entropy (during preview) and hip displacement entropy (during climbing). Data revealed statistically significant curvilinear relationships between both fingertip strength and gaze transition entropy, and fingertip strength, and hip displacement entropy. Visuo‐motor complexity is scaled by how close the individual must act relative to boundaries of what the environment affords and does not afford for action given the individual constraints. Future research should examine in greater detail relationships between action capabilities and functional movement variability.

Increased Risk of Musculoskeletal Injury Following Sport-Related Concussion: A Perception-Action Coupling Approach

Recent studies have concluded that athletes have increased risk of musculoskeletal injury following sport-related concussion. While an underlying explanation is still unknown, perceptual-motor control may be implicated in this increased risk. Some authors have purported that indirect perception (i.e., a "top-down" view of neuromuscular control) may be disrupted following sport-related concussion. Direct perception theory states that the athlete and environment are inextricably linked in a continuous perception-action coupling loop. That is, the athlete is able to directly perceive opportunities for action (e.g., "affordances") in the environment. Based on these notions, the aim of the current paper was to introduce a theoretical model that argues that sport-related concussion may dysregulate the direct perception process, potentially increasing behavioral risk of musculoskeletal injury during sport. Our model is integrated with a sport-related concussion clinical treatment model, which highlights individualized profiles that characterize the heterogeneous response to sport-related concussion. These profiles have a typical constellation of symptoms (e.g., anxiety, fatigue, ocular dysfunction, etc.), which themselves have been associated with disrupted perception-action coupling, independent of sport-related concussion. Therefore, we argue that athletes who have not re-established perception-action coupling loops following sport-related concussion may be at increased risk of subsequent musculoskeletal injury.

Hopf Bifurcations in Complex Multiagent Activity: The Signature of Discrete to Rhythmic Behavioral Transitions

Most human actions are composed of two fundamental movement types, discrete and rhythmic movements. These movement types, or primitives, are analogous to the two elemental behaviors of nonlinear dynamical systems, namely, fixed-point and limit cycle behavior, respectively. Furthermore, there is now a growing body of research demonstrating how various human actions and behaviors can be effectively modeled and understood using a small set of low-dimensional, fixed-point and limit cycle dynamical systems (differential equations). Here, we provide an overview of these dynamical motorprimitives and detail recent research demonstrating how these dynamical primitives can be used to model the task dynamics of complex multiagent behavior. More specifically, we review how a task-dynamic model of multiagent shepherding behavior, composed of rudimentary fixed-point and limit cycle dynamical primitives, can not only effectively model the behavior of cooperating human co-actors, but also reveals how the discovery and intentional use of optimal behavioral coordination during task learning is marked by a spontaneous, self-organized transition between fixed-point and limit cycle dynamics (i.e., via a Hopf bifurcation).

Locomotor Coordination, Visual Perception and Head Stability during Running

Perception and action are coupled such that information from the perceptual system is related to the dynamics of action in order to regulate behavior adaptively. Using running as a model of a cyclic behavior, this coupling involves a continuous, cyclic relationship between the runner’s perception of the environment and the necessary adjustments of the body that ultimately result in a stable pattern of behavior. The purpose of this paper is to illustrate how individuals relate visual perception to rhythmic locomotor coordination patterns in conditions during which foot–ground collisions and visual task demands are altered. We review the findings of studies conducted to illustrate how humans change their behavior to maintain head stability during running with and without various degrees of visual challenge from the environment. Finally, we show that the human body adapts specific segment/joint configuration and coordination patterns to maintain head stability, both in the lower extremity and upper body segments, together with an increase in coordinative variability. These results indicate that in human locomotion, under higher speed (running) and visual task demands, systematic adaptations occur in the rhythmic coupling between the perceptual and movement systems.

Affordance-based versus current-future accounts of choosing whether to pursue or abandon the chase of a moving target

Affordance-based control and current-future control offer competing theoretical accounts of the visual control of locomotion. The aim of this study was to test predictions derived from these accounts about the necessity of self-motion (Experiment 1) and target-ground contact (Experiment 2) in perceiving whether a moving target can be intercepted before it reaches an escape zone. We designed a novel interception task wherein the ability to perceive target catchability before initiating movement was advantageous. Subjects pursued a target moving through a field in a virtual environment and attempted to intercept the target before it escaped into a forest. Targets were catchable on some trials but not others. If subjects perceived that they could not reach the target, they were instructed to immediately give up by pressing a button. After each trial, subjects received a point reward that incentivized them to pursue only those targets that were catchable. On the majority of trials, subjects either pursued and successfully intercepted the target or chose not to pursue at all, demonstrating that humans are sensitive to catchability while stationary. Performance also degraded when the target was floating rather than in contact with the ground. Both findings are incompatible with the current-future account and support the affordance-based account of choosing whether to pursue moving targets.

Age-related differences in the perception of gap affordances: Impact of standardized action capabilities on road-crossing judgements

Recent road-crossing literature has found that older adults show performance differences between estimation and perception-action tasks suggesting an age-related difficulty in accurately calibrating the information picked up from the surrounding environment to their action capabilities (Lobjois and Cavallo, 2009). The present study investigated whether participants could accurately perceive gap affordances via information that specifies the time-to-arrival of the approaching cars. To ensure the opportunities for action were the same across different age groups, independent of the actor's action capabilities, the action of crossing the road was standardised. A total of 45 participants (15 children, aged 10-12, 15 adults aged 19-39, 15 older adults aged 65+) were asked to judge, by pressing a button in a head-mounted display, whether the gap between oncoming cars afforded crossing. When the participant pressed the button, they moved across the road at a fixed speed. Adherence to a time-based variable (namely tau) explained 85% and 84% of the variance in both the children and adults' choices, respectively. Older adults tuned less into the time-based variable (tau) with it only accounting for 59% of the variance in road-crossing decisions. These findings suggest that, the ability to use tau information which specifies whether a gap affords crossing or not, deteriorates with age.

Perception of another person's maximum reach-with-jump height from walking kinematics

Humans can perceive affordances (possibilities for action) for themselves and others, including the maximum overhead height reachable by jumping (reach-with-jump height, RWJ). While observers can accurately perceive maximum RWJ for another person without previously seeing the person jump, estimates improve after viewing the person walk, suggesting there is structure in walking kinematics that is informative about the ability to produce vertical force for jumping. We used principal component analysis (PCA) to identify patterns in human walking kinematics that specify another person's maximum RWJ ability, and to determine whether athletes are more sensitive than non-athletes to these patterns. Kinematic data during treadmill walking were collected and submitted to PCA to obtain loading values for the kinematic time series variables on the first principal component. Kinematic data were also used to create point-light (PL) displays, in which the movement kinematics of PL walkers were manipulated using the obtained PCA loading values to determine how changes in body-segment movements impacted perception of maximum RWJ height. While manipulating individual segmental loadings in the PL displays did not substantially affect RWJ estimates, PL displays created by replacing the PCA loadings of a high-jumper with those of a low-jumper, and vice versa, resulted in corresponding reversals of participants' RWJ estimates, suggesting that the global structure of walking kinematics carries information about another's maximum RWJ height. Athletes exhibited greater sensitivity than controls to the kinematic manipulations, indicating that they are better attuned to useful kinematic information as a result of their sport experience.

Change in effectivity yields recalibration of affordance geometry to preserve functional dynamics

Mon-Williams and Bingham (Exp Brain Res 211(1):145-160, 2011) developed a geometrical affordance model for reaches-to-grasp, and identified a constant scaling relationship, P, between safety margins (SM) and available apertures (SM) that are determined by the sizes of the objects and the individual hands. Bingham et al. (J Exp Psychol Hum Percept Perform 40(4):1542-1550, 2014) extended the model by introducing a dynamical component that scales the geometrical relationship to the stability of the reaching-to-grasp. The goal of the current study was to explore whether and how quickly change in the relevant effectivity (functionally determined hand size = maximum grip) would affect the geometrical and dynamical scaling relationships. The maximum grip of large-handed males was progressively restricted. Participants responded to this restriction by using progressively smaller safety margins, but progressively larger P (= SM/AA) values that preserved an invariant dynamical scaling relationship. The recalibration was relatively fast, occurring over five trials or less, presumably a number required to detect the variability or stability of performance. The results supported the affordance model for reaches-to-grasp in which the invariance is determined by the dynamical component, because it serves the goal of not colliding with the object before successful grasping can be achieved. The findings were also consistent with those of Snapp-Childs and Bingham (Exp Brain Res 198(4):527-533, 2009) who found changes in age-specific geometric scaling for stepping affordances as a function of changes in effectivities over the life span where those changes preserved a dynamic scaling constant similar to that in the current study.

Don't Turn Blind! The Relationship Between Exploration Before Ball Possession and On-Ball Performance in Association Football

Visual exploratory action - scanning movements expressed through left and right rotation of the head - allows perception of a surrounding environment and supports prospective actions. In the dynamically changing football environment, the extent to which exploratory action benefits a player's subsequent performance with the ball is likely influenced by how and when the exploratory action occurs. Although few studies have examined the relationship between visual exploration and on-pitch football performance, it has been reported that a higher frequency of exploratory head movement up to 10-s before receiving the ball increases the likelihood of successful performance with the ball. This study investigated the relationship between head turn frequency and head turn excursion, and how and when exploratory head movement - within 10-s before ball possession - is related to performance with the ball in 11v11 match-play. Thirty-two semi-elite football players competed in 11v11 match-play. Head turn frequency and head turn excursion before ball possession were quantified with wearable inertial measurement units, and actions with the ball were coded via notational analysis. Odds ratio calculations were conducted to determine the associations between exploration variables and on-ball performance outcomes. A total of 783 actions with the ball were analyzed. Results revealed a strong relationship between head turn frequency and head turn excursion. Further, a higher than average head turn frequency and head turn excursion before receiving the ball resulted in a higher likelihood of turning with the ball, playing a pass in the attacking direction, and playing a pass to an area that is opposite to which it was received from. The strength of these outcomes varied for different time periods before receiving the ball. When players explored their environment with higher than average head turn frequency and excursion, they used more complex action opportunities afforded by the surrounding environment. Considerations for future research and practical implications are discussed.

Collision Avoidance With Multiple Walkers: Sequential or Simultaneous Interactions?

Collision avoidance between multiple walkers, such as pedestrians in a crowd, is based on a reciprocal coupling between the walkers with a continuous loop between perception and action. Such interpersonal coordination has previously been studied in the case of dyadic locomotor interactions. However, when walking through a crowd of people, collision avoidance is not restricted to dyadic interactions. We examined how dyadic avoidance (1 vs. 1) compared to triadic avoidance (1 vs. 2). Additionally, we examined how the dynamics of a passable gap between two walkers affected locomotor interactions. To this end, we manipulated the starting formation of two walkers that formed a potentially pass-able gap for the other walker. We analyzed the interactions in terms of the evolution over time of the Minimal Predicted Distance and the Dynamics of the Gap, which both provide information about what action is afforded (i.e., passing in front/behind and the pass-ability of the gap). Results showed that some triadic interactions invited for sequential interactions, resulting in avoidance strategies comparable with dyadic interactions. However, some formations resulted in simultaneous interactions where the dynamics of the pass-ability of the gap revealed that the coordination strategy emerged over time through the bi-directional interactions between all walkers. Future work should address which circumstances invite for simultaneous and which for sequential interactions between multiple walkers. This study contributed toward understanding how collision is avoided between multiple walkers at the level of the local interactions.

The History and Philosophy of Ecological Psychology

Ecological Psychology is an embodied, situated, and non-representational approach pioneered by J. J. Gibson and E. J. Gibson. This theory aims to offer a third way beyond cognitivism and behaviorism for understanding cognition. The theory started with the rejection of the premise of the poverty of the stimulus, the physicalist conception of the stimulus, and the passive character of the perceiver of mainstream theories of perception. On the contrary, the main principles of ecological psychology are the continuity of perception and action, the organism-environment system as unit of analysis, the study of affordances as the objects of perception, combined with an emphasis on perceptual learning and development. In this paper, first, we analyze the philosophical and psychological influences of ecological psychology: pragmatism, behaviorism, phenomenology, and Gestalt psychology. Second, we summarize the main concepts of the approach and their historical development following the academic biographies of the proponents. Finally, we highlight the most significant developments of this psychological tradition. We conclude that ecological psychology is one of the most innovative approaches in the psychological field, as it is reflected in its current influence in the contemporary embodied and situated cognitive sciences, where the notion of affordance and the work of E. J. Gibson and J. J. Gibson is considered as a historical antecedent.