Time course of the Simon effect in pointing movements for horizontal, vertical, and acoustic stimuli: evidence for a common mechanism

Motor demands influence conflict processing in a mouse-tracking Simon task

Previous studies have shown incorrect motor activation when making perceptual decisions under conflict, but the potential involvement of motor processes in conflict resolution is still unclear. The present study tested whether the effects of distracting information may be reduced when anticipated motor processing demands increase. Specifically, across two mouse-tracking Simon experiments, we manipulated blockwise motor demands (high vs. low) by requiring participants to move a mouse cursor to either large versus small (Experiment 1) or near versus far (Experiment 2) response boxes presented on the screen. We reasoned that participants would increase action control in blocks with high versus low motor demands and that this would reduce the distracting effect of location-based activation. The results support this hypothesis: Simon effects were reduced under high versus low motor demands and this modulation held even when controlling for time-varying fluctuations in distractor-based activation via distributional analyses (i.e., delta plots). Thus, the present findings indicate that anticipation of different motor costs can influence conflict processing. We propose that the competition between distractor-based and target-based activation is biased at premotor and/or motor stages in anticipation of motor demands, but also discuss alternative implementations of action control.

Revealing the effects of temporal orienting of attention on response conflict using continuous movements

Orienting attention in time enables us to prepare for forthcoming perception and action (e.g., estimating the duration of a yellow traffic light when driving). While temporal orienting can facilitate performance on simple tasks, its influence on complex tasks involving response conflict is unclear. Here, we adapted the flanker paradigm to a choice-reaching task where participants used a computer mouse to reach to the left or right side of the screen, as indicated by the central arrow presented with either the congruent or incongruent flankers. We assessed the effects of temporal orienting by manipulating goal-driven temporal expectation (using probabilistic variations in target timing) and stimulus-driven temporal priming (using sequential repetitions versus switches in target timing). We tested how temporal orienting influenced the dynamics of response conflict resolution. Recent choice-reaching studies have indicated that under response conflict, delayed movement initiation captures the response threshold adjustment process, whereas increased curvature toward the incorrect response captures the degree of coactivation of the response alternatives during the controlled response selection process. Both temporal expectation and priming reduced the initiation latency regardless of response conflict, suggesting that both lowered response thresholds independently of response conflict. Notably, temporal expectation, but not temporal priming, increased the curvature toward the incorrect response on incongruent trials. These results suggest that temporal orienting generally increases motor preparedness, but goal-driven temporal orienting particularly interferes with response conflict resolution, likely through its influence on response thresholds. Overall, our study highlights the interplay between temporal orienting and cognitive control in goal-directed action.

Design choices: Empirical recommendations for designing two-dimensional finger-tracking experiments

The continuous tracking of mouse or finger movements has become an increasingly popular research method for investigating cognitive and motivational processes such as decision-making, action-planning, and executive functions. In the present paper, we evaluate and discuss how apparently trivial design choices of researchers may impact participants' behavior and, consequently, a study's results. We first provide a thorough comparison of mouse- and finger-tracking setups on the basis of a Simon task. We then vary a comprehensive set of design factors, including spatial layout, movement extent, time of stimulus onset, size of the target areas, and hit detection in a finger-tracking variant of this task. We explore the impact of these variations on a broad spectrum of movement parameters that are typically used to describe movement trajectories. Based on our findings, we suggest several recommendations for best practice that avoid some of the pitfalls of the methodology. Keeping these recommendations in mind will allow for informed decisions when planning and conducting future tracking experiments.

Response mode modulates the congruency sequence effect in spatial conflict tasks: evidence from aimed-movement responses

The present study investigated how response mode determines the specificity of control responsible for the congruency sequence effect (CSE), especially when conflict arises from spatial dimensions. Horizontal and vertical Simon tasks were presented in turn, while response mode (Experiment 1) or task-relevant stimulus dimension (Experiment 2) was manipulated. All responses were made by aimed movements to make the relative salience of the horizontal and vertical dimensions equivalent regardless of response mode. The confound-minimized CSEs were significant only when the two tasks shared the same response mode, which did not vary as a function of task-relevant stimulus dimension. This result suggests that response mode determines the scope of control, as it reconfigures the representations of the task-irrelevant spatial dimensions (i.e., the horizontal and vertical dimensions), which is corroborated by distributional analyses. This response mode-specific control was also consistently found for the horizontal and vertical arrow versions of flanker-compatibility tasks in Experiment 3, in which conflict does not directly arise from the response dimension. Furthermore, the current findings revealed that the CSEs were more evident in movement times than in initiation times, which provides new insight on how control inhibits the response activated by a task-irrelevant stimulus dimension, especially at a motor level.

Beyond mean reaction times: Combining distributional analyses with processing stage manipulations in the Simon task

We combined analyses of reaction time (RT) distributions with experimental manipulations of different processing stages (perception, decision, motor execution) in a Simon task to investigate which changes in Simon effects could be explained entirely by fading irrelevant response activation. Consistent with fading activation accounts, the Simon effect on mean RT was usually smaller for conditions with slower responses (Expts. 1-3 but not Expt. 4), and delta plot analyses revealed that it was always smaller for the slower responses within each condition. Critically, however, these analyses also revealed that some experimental manipulations produced upward or downward shifts in the RT delta plots, thus altering the Simon effect on mean RT in ways that could not be explained by fading activation. The results demonstrate the power of combining RT distributional analyses with experimental manipulations to reveal mechanisms contributing to the Simon effect that would not be revealed using only mean RT. We consider alternatives to fading activation accounts of decreasing delta plots and discuss the contribution of different cognitive stages in modulating Simon effects.

Psychometrics of the continuous mind: Measuring cognitive sub-processes via mouse tracking

The measurement of psychological properties often relies on discrete measures, for example, answers in questionnaires or responses in tasks. This focus on discrete measures neglects information that is present in the process leading to an answer or a response. A method to trace such processes is mouse tracking. Mouse tracking promises to open a continuous window onto the processes leading from a stimulus to a response. However, most mouse-tracking studies fall short of the promise to extract dynamic psychometrically valid markers for the different sub-processes, which are intertwined on the way to the final response. Here we used time-continuous multiple regression (TCMR) to extract dynamic markers for the different sub-processes leading to a response. From these markers, we extracted information about the timing, the duration, and the strength of the influence of the different sub-processes. We evaluated these dynamic measures of sub-processes for their psychometric properties, i.e. reliability, which is a basis for their use in the study of individual differences. Furthermore, we applied these dynamic measures in a group-level study to identify differences in the sub-processes of resolving response conflict between groups performing either a Simon or a flanker task. We found specific temporal patterns that match predictions from a conceptual model of these tasks. We concluded that the extracted information from mouse movements could be used as psychometrically valid dynamic measures of psychological properties and their differences across individuals and situations.A software toolbox to perform the described analyses in Matlab is provided (osf.io/5e3vn).

Lost to translation: How design factors of the mouse-tracking procedure impact the inference from action to cognition

From an embodiment perspective, action and cognition influence each other constantly. This interaction has been utilized in mouse-tracking studies to infer cognitive states from movements, assuming a continuous manifestation of cognitive processing into movement. However, it is mostly unknown how this manifestation is affected by the variety of possible design choices in mouse-tracking paradigms. Here we studied how three design factors impact the manifestation of cognition into movement in a Simon task with mouse tracking. We varied the response selection (i.e., with or without clicking), the ratio between hand and mouse cursor movement, and the location of the response boxes. The results show that all design factors can blur or even prevent the manifestation of cognition into movement, as reflected by a reduction in movement consistency and action dynamics, as well as by the adoption of unsuitable movement strategies. We conclude that deliberate and careful design choices in mouse-tracking experiments are crucial to ensuring a continuous manifestation of cognition in movement. We discuss the importance of developing a standard practice in the design of mouse-tracking experiments.

Stuck at the starting line: How the starting procedure influences mouse-tracking data

Mouse-tracking is an increasingly popular method to trace cognitive processes. As is common for a novel method, the exact methodological procedures employed in an individual study are still relatively idiosyncratic and the effects of different methodological setups on mouse-tracking measures have not been explored so far. Here, we study the impact of one commonly occurring methodological variation, namely whether participants have to initiate their mouse movements to trigger stimulus presentation (dynamic starting condition) or whether the stimulus is presented automatically after a fixed delay and participants can freely decide when to initiate their movements (static starting condition). We compared data from a previous study in which participants performed a mouse-tracking version of a Simon task with a dynamic starting condition to data from a new study that employed a static starting condition in an otherwise identical setup. Results showed reliable Simon effects and Congruency Sequence effects on response time (RT) and discrete trial-level mouse-tracking measures (i.e., average deviation) in both starting conditions. In contrast, within-trial continuous measures (i.e., extracted temporal segments) were weaker and occurred in a more temporally compressed way in the static compared to the dynamic starting condition. This was in line with generally less consistent movements within and across participants in the static compared to the dynamic condition. Our results suggest that studies that use within-trial continuous measures to assess dynamic aspects of mouse movements should apply dynamic starting procedures to enhance the leakage of cognitive processing into the mouse movements.

Response Inhibition as a Function of Movement Complexity and Movement Type Selection

This study aims to determine whether response inhibition shows the same degree of effectiveness for two sources of motor complexity: (1) Movement complexity, which is measured through two actions with different motor requirements (simple lifting action vs. complex reaching action), and (2) Movement type selection, which is measured in movements performed separately (no active-movement type selection) vs. selectively (active-movement type selection). Activation–suppression model was tested in three experiments to measure activation of the preponderant responses and subsequent suppression in a Simon task. More errors and higher magnitude of congruence effect (which reflects greater effectiveness of response suppression) were expected for more difficult motor conditions. Reaction time, movement time, kinematic errors, and movement errors were recorded. Results of Experiment 1, in which movement type selection was not active, showed that both movements did not differ in their activation and suppression, as they presented similar kinematic error rates and Simon effects. Experiment 2, in which movement type selection was active, resulted in a higher kinematic error rate and higher magnitude of Simon effect in lifting. These results were confirmed in Experiment 3, in which participants performed all experimental motor complexity conditions. Finally, Experiment 4 showed that responses with similar movement complexity did not differ in their activation and suppression, even when movement type selection was active. Thus, the present study provides evidence on the varying effectiveness of response inhibition as a function of movement complexity, but only in demanding situations in which movement type selection is active. These results can be attributed to a top-down strategy to minimize error for actions most prone to develop kinematic error.

The impact of anatomical and spatial distance between responses on response conflict

Different features of objects can be associated with different responses, so that their concurrent presence results in conflict. The Simon effect is a prominent example of this type of response conflict. In two experiments, we ask whether it is modulated by the anatomical or spatial relation between responses. Predictions were derived from an extended variant of the leaky, competing accumulator (LCA) model proposed by Usher and McClelland (Psychological Review, 108, 550-592, 2001). The relation between responses was represented by the lateral-inhibition parameter of the model. For the anatomical distance between responses the expectations were largely confirmed, but not for spatial distance. First, the Simon effect was stronger when responses were performed with two fingers of the same hand than with different hands. Second, the Simon effect was larger only for responses with different hands at short reaction times and disappeared at long ones, whereas for responses with fingers of the same hand, the Simon effect was essentially the same for shorter and longer reaction times. This difference resulted in smaller variability of reaction times in noncorresponding than in corresponding conditions. The dependence of decision processes, as modelled by the LCA model, on the anatomical relation between responses supports the broad hypothesis that the accumulation of evidence on the state of the world is intricately linked with the activation of response codes, that is, the selection of the appropriate actions.

Visual versus auditory Simon effect: A behavioural and physiological investigation

This study investigated whether the visual and auditory Simon effects could be accounted for by the same mechanism. In a single experiment, we performed a detailed comparison of the visual and the auditory Simon effects arising in behavioural responses and in pupil dilation, a psychophysiological measure considered as a marker of the cognitive effort induced by conflict processing. To address our question, we performed sequential and distributional analyses on both reaction times and pupil dilation. Results confirmed that the mechanisms underlying the visual and auditory Simon effects are functionally equivalent in terms of the interaction between unconditional and conditional response processes. The two modalities, however, differ with respect to the strength of their activation and inhibition. Importantly, pupillary data mirrored the pattern observed in behavioural data for both tasks, adding physiological evidence to the current literature on the processing of visual and auditory information in a conflict task.

Space and Motion Stimulus-Response Correspondence (SRC) Effects in a Single Task

Previous research indicated that congruency between stimulus location and response position (spatial stimulus-response correspondence [SRC]) and stimulus motion and response movement congruency (motion SRC) are distinct SRC phenomena. This study further explored this issue and tested whether these two SRC effects are independent. This was conducted by investigating these two SRC effects in a single task. A stimulus with leftward or rightward motion was presented on the left or the right side of the screen and the participant had to move the joysticks held with the left and right hands leftward or rightward in response to the stimulus color. In this setting, the stimulus and response shared two types of correspondence: spatial and motion. The results demonstrated that two SRC effects occurred and interacted (interaction evident only in reaction times [RTs]). RT distribution analysis and accuracy delta plots for each SRC effect indicated that spatial and motion SRC are distinct phenomena based on different processes.

Stimulus-Response Compatibility Effect in the Near-Far Dimension: A Developmental Study

The present study investigates the developmental aspect of stimulus-response compatibility (SRC) effect in 8-11-years-old children. The task consisted in manually responding to the color of a pawn presented on a chessboard at different distances. Manual responses were provided by reaching a proximal or distal location depending on the color of the stimulus. We found that reaction time was affected by the conflict generated by the response suggested by the location of the stimulus and the response required according to its color. This was not the case for movement time despite we found a higher rate of long duration movements in the incongruent than in the congruent spatial condition. The SRC effect was, however, observed in children older than 10 years old. These findings provide additional evidence for a reorganization of the perceptual system during the period of 8-10 years, integrating progressively multimodal information and preparing more efficiently the body to act in the environment.

The self in conflict: actors and agency in the mediated sequential Simon task

Executive control refers to the ability to withstand interference in order to achieve task goals. The effect of conflict adaptation describes that after experiencing interference, subsequent conflict effects are weaker. However, changes in the source of conflict have been found to disrupt conflict adaptation. Previous studies indicated that this specificity is determined by the degree to which one source causes episodic retrieval of a previous source. A virtual reality version of the Simon task was employed to investigate whether changes in a visual representation of the self would similarly affect conflict adaptation. Participants engaged in a mediated Simon task via 3D "avatar" models that either mirrored the participants' movements, or were presented statically. A retrieval cue was implemented as the identity of the avatar: switching it from a male to a female avatar was expected to disrupt the conflict adaptation effect (CAE). The results show that only in static conditions did the CAE depend on the avatar identity, while in dynamic conditions, changes did not cause disruption. We also explored the effect of conflict and adaptation on the degree of movement made with the task-irrelevant hand and replicated the reaction time pattern. The findings add to earlier studies of source-specific conflict adaptation by showing that a visual representation of the self in action can provide a cue that determines episodic retrieval. Furthermore, the novel paradigm is made openly available to the scientific community and is described in its significance for studies of social cognition, cognitive psychology, and human-computer interaction.

Suppression of irrelevant activation in the horizontal and vertical Simon task differs quantitatively not qualitatively

The Simon effect is usually explained by the assumption that the irrelevant stimulus location automatically activates the corresponding response. In the case of incongruent stimulus-response assignments automatically activated responses therefore have to be suppressed to ensure correct responses. This account, however, has been called into question for other than horizontally arranged visual Simon tasks. We investigated whether there is a qualitative or quantitative difference in suppression of irrelevant activation between horizontally and vertically arranged Simon tasks, using delta-function analyses. Sequential analyses revealed suppression after incongruent trials in both tasks, supporting the idea of a quantitative rather than a qualitative difference between the tasks. We conclude that automatic response activation is weaker in vertical tasks resulting in lower inhibitory demands as compared to horizontal tasks.

Effects of spatial response coding on distractor processing: evidence from auditory spatial negative priming tasks with keypress, joystick, and head movement responses

Prior studies of spatial negative priming indicate that distractor-assigned keypress responses are inhibited as part of visual, but not auditory, processing. However, recent evidence suggests that static keypress responses are not directly activated by spatially presented sounds and, therefore, might not call for an inhibitory process. In order to investigate the role of response inhibition in auditory processing, we used spatially directed responses that have been shown to result in direct response activation to irrelevant sounds. Participants localized a target sound by performing manual joystick responses (Experiment 1) or head movements (Experiment 2B) while ignoring a concurrent distractor sound. Relations between prime distractor and probe target were systematically manipulated (repeated vs. changed) with respect to identity and location. Experiment 2A investigated the influence of distractor sounds on spatial parameters of head movements toward target locations and showed that distractor-assigned responses are immediately inhibited to prevent false responding in the ongoing trial. Interestingly, performance in Experiments 1 and 2B was not generally impaired when the probe target appeared at the location of the former prime distractor and required a previously withheld and presumably inhibited response. Instead, performance was impaired only when prime distractor and probe target mismatched in terms of location or identity, which fully conforms to the feature-mismatching hypothesis. Together, the results suggest that response inhibition operates in auditory processing when response activation is provided but is presumably too short-lived to affect responding on the subsequent trial.

The speed and accuracy of perceptual decisions in a random-tone pitch task

Research in perceptual decision making is dominated by paradigms that tap the visual system, such as the random-dot motion (RDM) paradigm. In this study, we investigated whether the behavioral signature of perceptual decisions in the auditory domain is similar to those observed in the visual domain. We developed an auditory version of the RDM task, in which tones correspond to dots and pitch corresponds to motion (the random-tone pitch task, RTP). In this task, participants have to decide quickly whether the pitch of a “sound cloud” of tones is moving up or down. Stimulus strength and speed–accuracy trade-off were manipulated. To describe the relationship between stimulus strength and performance, we fitted the proportional-rate diffusion model to the data. The results showed a close coupling between stimulus strength and the speed and accuracy of perceptual decisions in both tasks. Additionally, we fitted the full drift diffusion model (DDM) to the data and showed that three of the four participants had similar speed–accuracy trade-offs in both tasks. However, for the RTP task, drift rates were larger and nondecision times slower, suggesting that some DDM parameters might be dependent on stimulus modality (drift rate and nondecision time), whereas others might not be (decision bound). The results illustrate that the RTP task is suitable for investigating the dynamics of auditory perceptual choices. Future studies using the task might help to investigate modality-specific effects on decision making at both the behavioral and neuronal levels.

Dynamic structure of joint-action stimulus-response activity

The mere presence of a co-actor can influence an individual’s response behavior. For instance, a social Simon effect has been observed when two individuals perform a Go/No-Go response to one of two stimuli in the presence of each other, but not when they perform the same task alone. Such effects are argued to provide evidence that individuals co-represent the task goals and the to-be-performed actions of a co-actor. Motivated by the complex-systems approach, the present study was designed to investigate an alternative hypothesis — that such joint-action effects are due to a dynamical (time-evolving) interpersonal coupling that operates to perturb the behavior of socially situated actors. To investigate this possibility, participants performed a standard Go/No-Go Simon task in joint and individual conditions. The dynamic structure of recorded reaction times was examined using fractal statistics and instantaneous cross-correlation. Consistent with our hypothesis that participants responding in a shared space would become behaviorally coupled, the analyses revealed that reaction times in the joint condition displayed decreased fractal structure (indicative of interpersonal perturbation processes modulating ongoing participant behavior) compared to the individual condition, and were more correlated across a range of time-scales compared to the reaction times of pseudo-pair controls. Collectively, the findings imply that dynamic processes might underlie social stimulus-response compatibility effects and shape joint cognitive processes in general.

Space positional and motion SRC effects: A comparison with the use of reaction time distribution analysis

The analysis of reaction time (RT) distributions has become a recognized standard in studies on the stimulus response correspondence (SRC) effect as it allows exploring how this effect changes as a function of response speed. In this study, we compared the spatial SRC effect (the classic Simon effect) with the motion SRC effect using RT distribution analysis. Four experiments were conducted, in which we manipulated factors of space position and motion for stimulus and response, in order to obtain a clear distinction between positional SRC and motion SRC. Results showed that these two types of SRC effects differ in their RT distribution functions as the space positional SRC effect showed a decreasing function, while the motion SRC showed an increasing function. This suggests that different types of codes underlie these two SRC effects. Potential mechanisms and processes are discussed.

Approach and avoidance movements are unaffected by cognitive conflict: a comparison of the Simon effect and stimulus-response compatibility

Participants in this study reached from central fixation to a lateral position that either contained or was opposite to the stimulus. Cognitive conflict was induced when the stimulus and response directions did not correspond. In the Simon task, the response direction was cued by the color of the lateral stimulus, and corresponding and noncorresponding trials varied randomly in the same block of trials, resulting in high uncertainty and long reaction times (RTs). In the stimulus-response compatibility (SRC) task, participants reached toward or away from the stimulus in separate blocks of trials, resulting in low uncertainty and short RTs. In the SRC task, cognitive conflict in noncorresponding trials slowed down RTs but hardly affected reach trajectories. In the Simon task, both RTs and reach trajectories were strongly influenced by stimulus-response correspondence. Despite the overall longer RTs in the Simon task, reaches were less direct and deviated toward the stimulus in noncorresponding trials. Thus, cognitive conflict was resolved before movement initiation in the SRC task, whereas it leaked into movement execution in the Simon task. Current theories of the Simon effect, such as the gating of response activation or response code decay, are inconsistent with our results. We propose that the SRC task was decomposed as approaching and avoiding the stimulus, which is sustained by stereotyped visuomotor routines. With complex stimulus-response relationships (Simon task), responses had to be coded as leftward and rightward, with more uncertainty about how to execute the action. This uncertainty permitted cognitive conflict to leak into the movement execution.

When predictive mechanisms go wrong: disordered visual synchrony thresholds in schizophrenia

Patients with schizophrenia display an impaired sense of temporal continuity, and we showed that they judge events as being simultaneous even in case of large onset asynchronies. We check here whether this means a fusion of events in time, or on the contrary, a segregation of events and a deficit in coding time-event structure. Subjects decided whether 2 squares were displayed simultaneously or asynchronously on the screen and gave their response by hitting a left or right response key. The implicit processing of asynchrony was explored by means of the Simon effect, which refers to the finding that manual responses are biased to the side of the stimulus. We checked whether responses were biased to the side of the first or second square, when squares were asynchronous and displayed on opposite sides. Results revealed an enlarged time window in patients irrespective of the squares' position (intra- vs interhemispheric presentation). But for asynchronies eliciting "synchronous" judgments, patients' responses were biased to the side of the first square. In contrast, controls were biased in all cases to the side of the second square. The inverse effects observed below thresholds in patients and controls cannot be attributed to a generalized deficit. In controls, elementary predictive mechanisms would allow anticipation of upcoming events, whereas patients appear to process squares as if isolated rather than following each other. Predictive mechanisms would be impaired in patients, who would rather rely on reactive mechanisms in order to perceive asynchrony.

Affective states leak into movement execution: automatic avoidance of threatening stimuli in fear of spider is visible in reach trajectories

Approach-like actions are initiated faster with stimuli of positive valence. Conversely, avoidance-like actions are initiated faster with threatening stimuli of negative valence. We went beyond reaction time measures and investigated whether threatening stimuli also affect the way in which an action is carried out. Participants moved their hand either away from the picture of a spider (avoidance) or they moved their hand toward the picture of a spider (approach). We compared spider-fearful participants to non-anxious participants. When reaching away from the threatening spider picture, spider-fearful participants moved more directly to the target than controls. When reaching toward the threatening spider, spider-fearful participants moved less directly to the target than controls. Some conditions that showed clear differences in movement trajectories between spider-fearful and control participants were devoid of differences in reaction time. The deviation away from threatening stimuli provides evidence for the claim that affective states like fear leak into movement programming and produce deviations away from threatening stimuli in movement execution. Avoidance of threatening stimuli is rapidly integrated into ongoing motor behaviour in order to increase the distance between the participant's body and the threatening stimulus.

Reaction time distribution analysis of spatial correspondence effects

Since 1994, group reaction time (RT) distribution analyses of spatial correspondence effects have been used to evaluate the dynamics of the spatial Simon effect, a benefit of correspondence of stimulus location information with response location for tasks in which stimulus location is irrelevant. We review the history and justification for analyzing group RT distributions and clarify which conditions result in the Simon effect decreasing across the distribution and which lead to flat or increasing functions. Although the standard left-right Simon effect typically yields a function for which the effect decreases as RT increases, in most other task variations, the Simon effect remains stable or increases across the RT distribution. Studies that have used other means of evaluating the temporal dynamics of the Simon effect provide converging evidence that the changes in the Simon effect across the distribution are due mainly to temporal activation properties, an issue that has been a matter of some dispute.

Colour Correspondence Effects between Controlled Objects and Targets

It is increasingly popular to use movement trajectories as a measure of mental processes related to task performance. Often this is accomplished by moving a cursor to a target on a computer screen. However, the relation between features of the cursor and the targets is rarely, if at all, considered. In five experiments, we examined whether moving a cursor to a target was affected by the relation between their colours, even when this relation was task irrelevant. In Experiments 1–3, a mouse-controlled cursor was moved to one of two coloured targets. Results showed colour correspondence effects in latency to initiate a response, duration of movement times, and movement trajectories when the relationship between cursor and target colours was task relevant (Experiment 1) and when only the cursor colour was task relevant (Experiment 2), but not when only the target was task relevant (Experiment 3). Follow-up experiments using single targets showed that colour correspondence effects occurred as long as attention was dedicated to the colour of the cursor, even when neither the cursor nor the target colour was relevant to selecting the correct movement (Experiments 4 and 5). Furthermore, when the relation between cursor and target colours is task irrelevant, colour correspondence effects for response initiation times are uncorrelated with those for movement times and movement trajectories. We interpret the observed correspondence effect in terms of response coding, although attention cueing may also play a role, and suggest that greater consideration of cursor features is needed when examining movement trajectories in choice reaction tasks.

Effects of Saccades and Response Type on the Simon Effect: If you Look at the Stimulus, the Simon Effect May be Gone

The Simon effect has most often been investigated with key-press responses and eye fixation. In the present study, we asked how the type of eye movement and the type of manual response affect response selection in a Simon task. We investigated three eye movement instructions (spontaneous, saccade, and fixation) while participants performed goal-directed (i.e., reaching) or symbolic (i.e., finger-lift) responses. Initially, no oculomotor constraints were imposed, and a Simon effect was present for both response types. Next, eye movements were constrained. Participants had to either make a saccade toward the stimulus or maintain gaze fixed in the screen centre. While a congruency effect was always observed in reaching responses, it disappeared in finger-lift responses. We suggest that the redirection of saccades from the stimulus to the correct response location in noncorresponding trials contributes to the Simon effect. Because of eye–hand coupling, this occurred in a mandatory manner with reaching responses but not with finger-lift responses. Thus, the Simon effect with key-presses disappears when participants do what they typically do—look at the stimulus.

Action plans produce separate Simon effects for picking up and transporting objects

A common type of interaction with the environment is reaching to move an object from one location to another. We investigated the influence of spatial stimulus-response (S-R) compatibility effects on the planning of such multi-reach actions. Participants responded to a cue on their left or right side by picking up a bean (initial reach) and then placing it in a container (goal reach). In three experiments, the initial reach and the goal reach were varied so that both reaches were to opposite sides (Exp 1), the initial reach was neutral (Exp 2), and both the initial and goal reaches were on the same side (Exp 3). The participants' reaction time to begin the initial reach was measured. Results showed that the spatial compatibility between the cue and both the initial and goal reaches contribute to the reaction time, with the relation between the cue and the initial reach playing a dominant role.