Simon-like and functional affordance effects with tools: The effects of object perceptual discrimination and object action state

In the present study two separate stimulus–response compatibility effects (functional affordance and Simon-like effects) were investigated with centrally presented pictures of an object tool (a torch) characterized by a structural separation between the graspable portion and the goal-directed portion. In Experiment 1, participants were required to decide whether the torch was red or blue, while in Experiment 2 they were required to decide whether the torch was upright or inverted. Our results showed that with the same stimulus two types of compatibility effect emerged: one based on the direction signalled by the goal-directed portion of the tool (a Simon-like effect as observed in Experiment 1), and the other based on the actions associated with an object (a functional affordance effect as observed in Experiment 2). Both effects emerged independently of the person's intention to act on the stimulus, but depended on the stimulus properties that were processed in order to perform the task.     

The role of attention in the occurrence of the affordance effect

It has been demonstrated that visual objects activate responses spatially corresponding to the orientation (left or right) of their graspable parts. To investigate the role of attention orienting in the generation of this effect, which we will refer to as affordance effect, we ran three experiments in which the target stimulus could either correspond or not with a dynamic event capturing attention. Participants were required to press a left or right key according to the vertical orientation (upward or inverted) of objects presented with their handles oriented to the right or to the left. In Experiments 1 and 2, the objects were located above or below fixation, while in Experiment 3, to assess the contemporary presence of the affordance and Simon effects, the objects were located to the left or right of fixation. The results showed that while the affordance effect, when evident, was always relative to the target object, irrespective of its attentional capturing properties, the Simon effect occurred relative to the event capturing attention. These findings suggest that automatic and controlled processes of visual attention may play a differential role in the occurrence of the two effects.     

Separate Pathways for the Processing of Affordance of Neutral and Dangerous Object

Previous studies have shown that observation of object automatically elicits the activation of a reach-to-grasp response specifically directed to interact with the object, which is termed affordance. Recent findings provide evidences that even dangerous objects can evoke aversive affordances. However, these studies only focused on avoidance effect emerged with dangerous objects. It remains unclear whether the neutral object and dangerous object share a common mechanism for the processing of affordance information. The affordance effect is considered to be a type of conflict between the afforded response and the response required by the task. In a symbol judgment task, we simultaneously presented the neutral object and dangerous object to investigate whether the congruency sequence effects (congruency effects following incongruent trials are smaller than those following congruent trials) occurred across the two types of affordance conflict, which is typically assumed that such flexible adjustments can only be observed between the same conflict types. It was found that congruency sequence effects were only generated between the same types of affordance conflict (e.g., neutral object or dangerous object), but not between two different affordance conflict types (e.g., neutral object and dangerous object). These results indicate there may be two different pathways for the processing of affordance of the neutral and dangerous object.     

Motor inhibition associated with the affordance of briefly displayed objects

Research has demonstrated that left- and right-hand responses are facilitated when they are performed with the hand compatible with the orientation of a viewed object. This suggests that graspable objects automatically activate the motor representations that correspond to their orientation. It has recently been proposed that similar positive stimulus–response compatibility effects (PCE) may turn into negative compatibility effects (NCE) when a prime object is displayed very briefly. These NCEs are suggested to reflect motor inhibition mechanisms—motor activation triggered by briefly viewed objects may be treated by the motor system as unwanted, and thus it is rapidly inhibited. We examined whether the motor activation triggered by the orientation of a task-irrelevant object is similarly inhibited when the object is displayed briefly. In Experiment 1, a NCE was observed between the orientation of an object and the responding hand when the object was displayed for 30 or 70 ms. The effect turned into a PCE when the object was displayed for 370 ms. Experiment 2 confirmed that this motor inhibition effect was produced by the handle affordance of the object rather than some abstract visual properties of the object.     

Motor inhibition associated with the affordance of briefly displayed objects

Research has demonstrated that left- and right-hand responses are facilitated when they are performed with the hand compatible with the orientation of a viewed object. This suggests that graspable objects automatically activate the motor representations that correspond to their orientation. It has recently been proposed that similar positive stimulus-response compatibility effects (PCE) may turn into negative compatibility effects (NCE) when a prime object is displayed very briefly. These NCEs are suggested to reflect motor inhibition mechanisms--motor activation triggered by briefly viewed objects may be treated by the motor system as unwanted, and thus it is rapidly inhibited. We examined whether the motor activation triggered by the orientation of a task-irrelevant object is similarly inhibited when the object is displayed briefly. In Experiment 1, a NCE was observed between the orientation of an object and the responding hand when the object was displayed for 30 or 70 ms. The effect turned into a PCE when the object was displayed for 370 ms. Experiment 2 confirmed that this motor inhibition effect was produced by the handle affordance of the object rather than some abstract visual properties of the object.     

Gradations of emulation learning in infants' imitation of actions on objects

This study explored different gradations of emulation in the imitation of actions on objects by 17-month-olds. Experiment 1 established levels of behavioral reproduction following prerecorded video demonstrations similar to those levels following live demonstrations. In Experiment 2, two digitally modified videos, where object movements or body movements critical to producing the target action were highlighted in isolation, were developed. Infants produced the target action equally frequently by observing the object movement video and observing the unmodified video. In contrast, their performance was much less successful based on the body movement video. In Experiment 3, the performance obtained following the object movement video was similar to that following a further video that emphasized the object movements produced in unsuccessful attempts to produce the target action. These findings suggest that emulation in the form of object movement reenactment or affordance learning plays a role in the social learning of actions on objects during infancy.     

Electrophysiological examination of embodiment in vision and action

A wealth of behavioral data has shown that the visual properties of objects automatically potentiate motor actions linked with them, but how deeply are these affordances embedded in visual processing? In the study reported here, we used electrophysiological measures to examine the time course of affordance resulting from the leftward or rightward orientation of the handles of common objects. Participants were asked to categorize those objects using a left- or right-handed motor response. Lateralized readiness potentials showed rapid motor preparation in the hand congruent with the affordance provided by the object only 100 to 200 ms after stimulus presentation and up to 400 ms before the actual response. Examination of event-related potentials also revealed an effect of handle orientation and response-hand congruency on the visual P1 and N1 components. Both of these results suggest that activity in the early sensory pathways is modulated by the action associations of objects and the intentions of the viewer.     

Perceptual priming is not a necessary consequence of semantic classification of pictures

Four experiments investigated how repetition priming of object recognition is affected by the task performed in the prime and test phases. In Experiment 1 object recognition was tested using both vocal naming and two different semantic decision tasks (whether or not objects were manufactured, and whether or not they would be found inside the house). Some aspects of the data were inconsistent with contemporary models of object recognition. Specifically, object priming was eliminated with some combinations of prime and test tasks, and there was no evidence of perceptual (as opposed to conceptual or response) priming in either semantic classification task, even though perceptual identification of the objects is required for at least one of these tasks. Experiment 2 showed that even when perceptual demands were increased by brief presentation, the inside task showed no perceptual priming. Experiment 3 showed that the inside task did not appear to be based on conceptual priming either, as it was not primed significantly when the prime decisions were made to object labels. Experiment 4 showed that visual sensitivity could be restored to the inside task following practice on the task, supporting the suggestion that a critical factor is whether the semantic category is preformed or must be computed. The results show that the visual representational processes revealed by object priming depend crucially on the task chosen.     

Action-related objects influence the distribution of visuospatial attention

Previous studies have shown that attention is drawn to the location of manipulable objects and is distributed across pairs of objects that are positioned for action. Here, we investigate whether central, action-related objects can cue attention to peripheral targets. Experiment 1 compared the effect of uninformative arrow and object cues on a letter discrimination task. Arrow cues led to spatial-cueing benefits across a range of stimulus onset asynchronies (SOAs: 0?ms, 120?ms, 400?ms), but object-cueing benefits were slow to build and were only significant at the 400-ms SOA. Similar results were found in Experiment 2, in which the targets were objects that could be either congruent or incongruent with the cue (e.g., screwdriver and screw versus screwdriver and glass). Cueing benefits were not influenced by the congruence between the cue and target, suggesting that the cueing effects reflected the action implied by the central object, not the interaction between the objects. For Experiment 3 participants decided whether the cue and target objects were related. Here, the interaction between congruent (but not incongruent) targets led to significant cueing/positioning benefits at all three SOAs. Reduced cueing benefits were obtained in all three experiments when the object cue did not portray a legitimate action (e.g., a bottle pointing towards an upper location, since a bottle cannot pour upwards), suggesting that it is the perceived action that is critical, rather than the structural properties of individual objects. The data suggest that affordance for action modulates the allocation of visual attention.     

Action-related objects influence the distribution of visuospatial attention

Previous studies have shown that attention is drawn to the location of manipulable objects and is distributed across pairs of objects that are positioned for action. Here, we investigate whether central, action-related objects can cue attention to peripheral targets. Experiment 1 compared the effect of uninformative arrow and object cues on a letter discrimination task. Arrow cues led to spatial-cueing benefits across a range of stimulus onset asynchronies (SOAs: 0 ms, 120 ms, 400 ms), but object-cueing benefits were slow to build and were only significant at the 400-ms SOA. Similar results were found in Experiment 2, in which the targets were objects that could be either congruent or incongruent with the cue (e.g., screwdriver and screw versus screwdriver and glass). Cueing benefits were not influenced by the congruence between the cue and target, suggesting that the cueing effects reflected the action implied by the central object, not the interaction between the objects. For Experiment 3 participants decided whether the cue and target objects were related. Here, the interaction between congruent (but not incongruent) targets led to significant cueing/positioning benefits at all three SOAs. Reduced cueing benefits were obtained in all three experiments when the object cue did not portray a legitimate action (e.g., a bottle pointing towards an upper location, since a bottle cannot pour upwards), suggesting that it is the perceived action that is critical, rather than the structural properties of individual objects. The data suggest that affordance for action modulates the allocation of visual attention.     

The predictive mirror: interactions of mirror and affordance processes during action observation

An important question for the study of social interactions is how the motor actions of others are represented. Research has demonstrated that simply watching someone perform an action activates a similar motor representation in oneself. Key issues include (1) the automaticity of such processes, and (2) the role object affordances play in establishing motor representations of others' actions. Participants were asked to move a lever to the left or right to respond to the grip width of a hand moving across a workspace. Stimulus-response compatibility effects were modulated by two task-irrelevant aspects of the visual stimulus: the observed reach direction and the match between hand-grasp and the affordance evoked by an incidentally presented visual object. These findings demonstrate that the observation of another person's actions automatically evokes sophisticated motor representations that reflect the relationship between actions and objects even when an action is not directed towards an object.     

Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence

Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (‘pinchable’) or whole-hand/power (‘graspable’) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450 ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450 ms (but not 150 ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect.     

Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence

Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (‘pinchable’) or whole-hand/power (‘graspable’) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450 ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450 ms (but not 150 ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect.     

Effects of action relations on the configural coding between objects

Configural coding is known to take place between the parts of individual objects but has never been shown between separate objects. We provide novel evidence here for configural coding between separate objects through a study of the effects of action relations between objects on extinction. Patients showing visual extinction were presented with pairs of objects that were or were not co-located for action. We first confirmed the reduced extinction effect for objects co-located for action. Consistent with prior results showing that inversion disrupts configural coding, we found that inversion disrupted the benefit for action-related object pairs. This occurred both for objects with a standard canonical orientation (e.g., teapot and teacup) and those without, but where grasping and using the objects was made more difficult by inversion (e.g., spanner and nut). The data suggest that part of the affordance effect may reflect a visuo-motor response to the configural relations between stimuli. Experiment 2 showed that distorting the relative sizes of the objects also reduced the advantage for action-related pairs. We conclude that action-related pairs are processed as configurations.     

Further evidence that object-based correspondence effects are primarily modulated by object location not by grasping affordance

Tipper, Paul and Hayes found object-based correspondence effects for door-handle stimuli for shape judgments but not colour. They reasoned that a grasping affordance is activated when judging dimensions related to a grasping action (shape), but not for other dimensions (colour). Cho and Proctor, however, found the effect with respect to handle position when the bases of the door handles were centred (so handles were positioned left or right; the base-centred condition) but not when the handles were centred (the object-centred condition), suggesting that the effect is driven by object location, not grasping affordance. We conducted an independent replication of Cho and Proctor's design, but with behavioural and event-related potential measures. Participants made shape judgments in Experiment 1 and colour judgments in Experiment 2 on the same door-handle objects. Correspondence effects on response time and errors were obtained in both experiments for the base-centred condition but not the object-centred condition. Effects were absent in the P1 and N1 data, which are consistent with the hypothesis of little binding between visual processing of grasping component and action. These findings question the grasping-affordance view but support a spatial-coding view, suggesting that correspondence effects are modulated primarily by object location.     

Searching for Memory Systems

The aim of the present study was to investigate the relationship between the affordance effect (i.e., the advantage for responses corresponding spatially with the location of an object's graspable part) and the Simon effect (i.e., the advantage for responses corresponding spatially with stimulus location) and to assess whether they both occur at the response selection stage. In two experiments participants were required to respond according to the vertical orientation (upward or inverted) of photographs of graspable objects, located to the left or right of fixation, with their handles oriented to the right or left. In Experiment 1 the response was a buttonpress; in Experiment 2 was a reaching movement. Our results showed that both Simon and affordance effects emerged in response times but not in movement times. In Experiment 1, the two effects did not interact, whereas a clear interaction emerged in Experiment 2. These results seem to suggest that the interaction between Simon and affordance effects may depend on the type of required action.     

Infant perception of causal motion produced by humans and inanimate objects

Both the movements of people and inanimate objects are intimately bound up with physical causality. Furthermore, in contrast to object movements, causal relationships between limb movements controlled by humans and their body displacements uniquely reflect agency and goal-directed actions in support of social causality. To investigate the development of sensitivity to causal movements, we examined the looking behavior of infants between 9 and 18 months of age when viewing movements of humans and objects. We also investigated whether individual differences in gender and gross motor functions may impact the development of the visual preferences for causal movements. In Experiment 1, infants were presented with walking stimuli showing either normal body translation or a “moonwalk” that reversed the horizontal motion of body translations. In Experiment 2, infants were presented with unperformable actions beyond infants’ gross motor functions (i.e., long jump) either with or without ecologically valid body displacement. In Experiment 3, infants were presented with rolling movements of inanimate objects that either complied with or violated physical causality. We found that female infants showed longer looking times to normal walking stimuli than to moonwalk stimuli, but did not differ in their looking time to movements of inanimate objects and unperformable actions. In contrast, male infants did not show sensitivity to causal movement for either category. Additionally, female infants looked longer at social stimuli of human actions than male infants. Under the tested circumstances, our findings indicate that female infants have developed a sensitivity to causal consistency between limb movements and body translations of biological motion, only for actions with previous visual and motor exposures, and demonstrate a preference toward social information.     

Transport and use of common objects: Influence of weight on action planning

Internal knowledge and visual cues about object's weight play an important role in grasping and lifting objects. It has been shown that both visual cues and internal knowledge might influence movement kinematics and force production depending on action goal (use vs. transport). However, there is little evidence about weight's influence on action planning as reflected by initiation time. In the present study we investigated this issue. In Experiment 1, participants had to grasp light and heavy objects (without moving them) to either use or transport them. In Experiment 2 we asked another group of participants to actually use or transport the same objects. We observed that initiation times were faster for heavy objects than for light objects in both the transport and use tasks, but only in Experiment 2. Thus, weight influenced the planning of use and transport actions, only when the end-goal of the action was really achieved. These data are incompatible with the hypothesis that only use actions are supported by stored object's representations. They rather suggest that in some circumstances, depending of the end-goal of the action and the physical constraints the planning of both use and transport actions are based on stored object representation.     

Conflict in object affordance revealed by grip force

Viewing objects can result in automatic, partial activation of motor plans associated with them-"object affordance". Here, we recorded grip force simultaneously from both hands in an object affordance task to investigate the effects of conflict between coactivated responses. Participants classified pictures of objects by squeezing force transducers with their left or right hand. Responses were faster on trials where the object afforded an action with the same hand that was required to make the response (congruent trials) compared to the opposite hand (incongruent trials). In addition, conflict between coactivated responses was reduced if it was experienced on the preceding trial, just like Gratton adaptation effects reported in "conflict" tasks (e.g., Eriksen flanker). This finding suggests that object affordance demonstrates conflict effects similar to those shown in other stimulus-response mapping tasks and thus could be integrated into the wider conceptual framework on overlearnt stimulus-response associations. Corrected erroneous responses occurred more frequently when there was conflict between the afforded response and the response required by the task, providing direct evidence that viewing an object activates motor plans appropriate for interacting with that object. Recording continuous grip force, as here, provides a sensitive way to measure coactivated responses in affordance tasks.     

Inhibition of return to occluded objects

Since many visual objects are vulnerable to occlusion, an active process that tracks objects behind occluders confers considerable ecological validity to the visual system. We studied this possibility by testing whether inhibition of return can be observed with occluded objects. In our experiments, two moving objects disappeared or reappeared behind occluders while a cue and a probe were presented. Contrary to the results of a previous study (Tipper, Weaver, Jerreat, & Burak, 1994), responses were consistently delayed for the cued object that was occluded when it was cued (Experiment 1), when it was probed (Experiment 2), or both (Experiment 3). These results suggest that attention can select occluded objects that are out of view. Our findings are in line with prior studies that have demonstrated similar perceptual/attentional effects for occluded objects, as well as for visible objects.