The visual size of graspable objects is needed to induce the potentiation of grasping behaviors even with verbal stimuli

Incompatibility Influences Cursor Placement When Pointing to Images of Cups

OBJECTIVE

As images are used within graphical user interfaces to signify menu selection, it is important to understand how image properties can influence cursor placement online.

BACKGROUND

Objects have multiple dimensions that create potential ambiguity and Stroop-like confusions for the operator if a previously habitual response conflicts with the required response.

METHODS

To examine the impact of compatibility and other contextual factors, 41 participants used a computer Mouse or touch screen to place the cursor upon images of full or empty cups that varied in size, and direction of handle.

RESULTS

Cursor placements took longer using the Mouse than touch screen. Although participants were placing the cursor on images, the size of the cup, whether it was empty or full, and the handle orientation interacted in their effects upon response duration and cursor placement. The effects of cup size reversed for empty cups or those with incompatible handles.

CONCLUSION

Context can influence cursor placement. Perceived spillability influenced precision requirements, and the cup handle can serve as target or a flanking distractor.

APPLICATION

Image content can influence screen hotspots. As performance can change with cup spillability, this bodes well for attempts to detect intent from cursor trajectories.

Stimulus-response compatibility effects during object semantic categorisation: Evocation of grasp affordances or abstract coding of object size?

When the size of visual objects matches the size of the response required to perform the task, a potentiation effect has been reported, with faster responses in compatible than incompatible situations. Size compatibility effects have been taken as evidence of close perception-action interrelations. However, it is still unclear whether the effect arises from abstract coding of the size of stimulus and response or from the evocation of grasp affordances from visual objects. We aimed to disentangle the two interpretations. Two groups of 40 young adults categorised small and large objects presented in standardised size as natural or artefact objects. One group categorised manipulable objects that may be associated with small or large size properties and evoke power or precision grasp affordances. The other group categorised non-manipulable objects that may only be associated with small or large size properties. Categorisation responses were made by reaching and grasping a monotonic cylindric device with a power or precision grip in a grasping condition and with large or small touch responses in a control condition. Compatibility effects were found in both grasping and control conditions, independently of the manipulability or category of objects. Participants were faster when the size of the expected response matched the size of the object than when they mismatched, especially for power grasps or whole-hand touch responses. Overall findings support the abstract coding hypothesis and suggest that compatibility between the conceptual size of the object and the size of the hand response is sufficient to facilitate semantic categorisation judgements.

The visual size is enough to automatically induce the potentiation of grasping behaviours

Seeing objects usually grasped with a power or a precision grip (e.g., an apple vs a cherry) potentiates power- and precision-grip responses, respectively. An embodied account suggests that this effect occurs because object conceptual representations would lie on a motor simulation process. A new account, named the size-coding account, argues that this effect could be rather due to an overlapping of size codes used to represent both manipulable objects and response options. In this article, we investigate whether this potentiation effect could be merely due to a low-level visual feature that favours a size-coding of stimuli: the visual size in which objects are presented. Accordingly, we conducted two experiments in which we presented highly elementary and non-graspable stimuli (i.e., ink spots) either large or small rather than graspable objects. Our results showed that the mere visual size automatically potentiates power- and precision-grip responses that are in line with the size-coding account of the potentiation effect of grasping behaviours. Moreover, these results appeal to improve the methodological control of the size of stimuli especially when researchers try to support the embodied account.

Manipulable objects can potentiate pointing and unusual grasping besides habitual grasping behaviors

People are faster to perform a precision grip when they see a cherry (i.e., a small graspable object) than to perform a power grip, and the reverse holds true when they see an apple (i.e., a large graspable object). This potentiation effect supports that object representations could include motor components that would be simulated when a graspable object is seen. However, the nature of these motor components remains unclear. The embodied account posits that seeing an object only potentiates the most frequent actions associated with it (i.e., usual actions). In contrast, the size-coding account posits that seeing an object potentiates any actions associated to spatial codes compatible with those associated to the objects. We conducted three experiments to disentangle these two alternative accounts. We especially varied the nature of the responses while participants saw either large or small graspable objects. Our results showed a potentiation effect when participants performed the usual grasping actions (Experiment 1: power and precision grip) but also when they performed unusual grasping actions (Experiment 2: grasping between the thumb and little finger) and even when they had to perform non-grasping actions (Experiment 3: pointing actions). By supporting the size-coding account, our contribution underlines the need for a better understanding of the nature of the motor components of object representations and for using a proper control condition (i.e., pointing action) before arguing that the embodied account convincingly explains the potentiation effect of grasping behaviors.

Hand constraint reduces brain activity and affects the speed of verbal responses on semantic tasks

According to the theory of embodied cognition, semantic processing is closely coupled with body movements. For example, constraining hand movements inhibits memory for objects that can be manipulated with the hands. However, it has not been confirmed whether body constraint reduces brain activity related to semantics. We measured the effect of hand constraint on semantic processing in the parietal lobe using functional near-infrared spectroscopy. A pair of words representing the names of hand-manipulable (e.g., cup or pencil) or nonmanipulable (e.g., windmill or fountain) objects were presented, and participants were asked to identify which object was larger. The reaction time (RT) in the judgment task and the activation of the left intraparietal sulcus (LIPS) and left inferior parietal lobule (LIPL), including the supramarginal gyrus and angular gyrus, were analyzed. We found that constraint of hand movement suppressed brain activity in the LIPS toward hand-manipulable objects and affected RT in the size judgment task. These results indicate that body constraint reduces the activity of brain regions involved in semantics. Hand constraint might inhibit motor simulation, which, in turn, would inhibit body-related semantic processing.