When left feels right: asymmetry in the affordance effect

Previous research has demonstrated the existence of the so-called affordance effect (faster response when the visual affordance of a graspable object (e.g., a pan) corresponds to the response location). It has been argued that the effect is due to abstract spatial coding of the position of the handle relative to the object instead of the grasping affordance. Our experiment tested the hypothesis that the affordance effect is not caused solely by abstract spatial coding but also by specific motor activation in response to the visual affordance. We assumed that, in the case of abstract spatial codes, response location and not hand distinction would be the critical factor for producing an affordance effect. In our experiment, bi-manual crossed/uncrossed responses to left/right symbols superimposed on a picture of a pan were used. The task was to attend to the symbol and to press a corresponding left/right button. Affordances of the pan were manipulated. A three-way interaction between side of affordance (left/right), mode of response (crossed/uncrossed hands), and response-affordance correspondence (corresponding/non-corresponding) showed a correspondence effect in the right affordance condition with hands uncrossed and no correspondence effect with hands crossed. The correspondence effect was obtained in the left affordance condition across hand positions that differed only by their magnitude. Overall, the results suggest that both mechanisms (grasping affordance and spatial codes) differentially contribute to the processing of an object with a graspable handle, depending on the affordance side and response hand.     

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.     

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.     

Response priming by supraliminal and subliminal action effects

Theories assuming an effect-based coding of action predict that motor responses become activated by the perception of the responses' sensory effects. In accordance with this prediction it was found that responding to a visual target is faster and more accurate when the target is briefly preceded by the visual effect of the required response. Most importantly, this effect-induced response priming was independent of prime perceptibility and it occurred even when the prime was not consciously discriminable. Beyond ruling out alternative interpretations of earlier induction studies in terms of deliberate response biases, this suggests that effect codes evoke their associated motor patterns in a highly automatic manner not affording conscious mediation. The results accord with a functional dissociation between the consciousness-mediated implementation and the consciousness-independent realization of action goals.     

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.     

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.     

Visual attention amplifies response priming of pointing movements to color targets

We studied the influence of spatial visual attention on the time course of primed pointing movements. We measured pointing responses to color targets preceded by color stimuli priming either the same response as the target or the opposite response. The effects of visual attention at the prime and target locations were studied by varying both the cue-prime and prime-target intervals when presenting either exogenous attentional cues or, in a separate experiment, endogenous cues whose processing was a precondition for performing the task. Pointing trajectories revealed large priming effects in which pointing responses were first controlled by prime signals and then captured in midflight by target signals. Priming effects were strongly amplified when the relevant prime locations were visually attended at optimal cue-prime SOAs, with attention modulating the entire time course of the primed pointing movements. We propose that visual attention amplifies the earliest waves of visuomotor feedforward information, elicited in turn by primes and by targets.     

Action priming by briefly presented objects

Three experiments investigated how visual objects prime the actions they afford. The principal concern was whether such visuomotor priming depends upon a concurrent visual input--as would be expected if it is mediated by on-line dorsal system processes. Experiment 1 showed there to be essentially identical advantages for making afforded over non-afforded responses when these were made to objects still in view and following brief (30 or 50 ms) object exposures that were backward masked. Experiment 2 showed that affordance effects were also unaffected by stimulus degradation. Finally, Experiment 3 showed there to be statistically equal effects from images of objects and their names. The results suggest that an active object representation is sufficient to generate affordance compatibility effects based on associated actions, whether or not the object is concurrently visible.     

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.     

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.     

Unconscious integration of pointing relation between two masked arrows

In the present study, by using a briefly masked prime display paradigm, we investigated whether the pointing relation (same or different) between two unconsciously perceived arrows in the prime could be processed. Since only motor response priming can reflect unconscious processing of two arrows’ pointing-direction relation (i.e., a relational integration), we could distinguish the motor response priming from the visual priming in this study which in other studies were not separated. We also manipulated the prime-to-target stimulus onset asynchronies (SOA) by using a 70?ms and a 180?ms SOA. In this experiment, two masked arrow signs pointing in the same or different directions (> > or > <) were simultaneously presented in the prime, followed by two arrow symbols also pointing in the same or different directions in the target. The participants were asked to decide whether the two arrows in the target were pointing in the same or different directions. The results did not show any visual priming effect, but did show that the unconsciously perceived pointing relation in the prime elicited a positive motor response priming effect in RT under the 70?ms SOA condition, and a negative motor response priming effect in accuracy under the 180?ms SOA condition. The results were discussed in terms of self-motor-inhibition (or mask-triggered inhibition) and attention mechanisms. Overall, this study indicated that the pointing relation between the two subliminal arrows in the prime could influence the subsequent responses to the target and suggested that people can integrate unconsciously perceived information.     

Hand-foot motor priming in the presence of temporary inability to use hands

To verify if the link between observed hand actions and executed foot actions found in aplasics is essentially induced by the constant use of foot substituting the hand, we investigated if the vision of a grasping hand is able to prime a foot response in normals. Participants were required to detect the time-to-contact of a hand grasping an object either with a suitable or a less suitable movement, an experimental paradigm known to induce a priming effect. Participants responded either with the hand or the foot, while having free or bound hands. Results showed that for hand responses motor priming effect was stronger when the hands were free, whereas for foot responses it was stronger when the hands were bound. These data are interpreted as a further evidence that a difficulty to move affects specific cognitive functions and that the vision of a grasping hand may prime a foot response.     

行动语义、客体背景和判断任务对客体动作承载性的影响

客体动作承载性指人们知觉客体时同时激活的针对客体的行动。当Gibson最初提出动作承载性概念时, 他认为客体的这种属性是可以自动激活的。然而近年来越来越多的证据显示, 在知觉和行动的关系中, 行动语义知识和客体所处背景对客体动作承载性具有调节作用, 表现在人们可以根据这些自上而下的信息选择针对客体的适当的行动。此外, 不同的判断任务在引发客体动作承载性效应上具有特异性, 表现在若判断任务仅需知觉客体表层属性时, 不能激活对客体的动作, 进而不能产生客体动作承载性; 若判断任务需要对客体进行深层加工时, 才会激活对客体的动作。未来研究还需要进一步探究行动语义知识和客体所处背景影响客体动作承载性发生的原因和机制, 以及不同判断任务中出现结果特异性的原因。     

Hand–foot motor priming in the presence of temporary inability to use hands

To verify if the link between observed hand actions and executed foot actions found in aplasics is essentially induced by the constant use of foot substituting the hand, we investigated if the vision of a grasping hand is able to prime a foot response in normals. Participants were required to detect the time-to-contact of a hand grasping an object either with a suitable or a less suitable movement, an experimental paradigm known to induce a priming effect. Participants responded either with the hand or the foot, while having free or bound hands. Results showed that for hand responses motor priming effect was stronger when the hands were free, whereas for foot responses it was stronger when the hands were bound. These data are interpreted as a further evidence that a difficulty to move affects specific cognitive functions and that the vision of a grasping hand may prime a foot response.     

Early activity in the lateralized readiness potential suggests prime-response retrieval as a source of negative priming

Negative priming (NP) refers to increased response time (RT) for a probe target that was a distractor in a preceding prime presentation (distractor-target shift, DT), compared to novel targets. The present study used the lateralized readiness potential (LRP) to investigate, in a four-choice identification task, a novel episodic-retrieval explanation of NP introduced by Rothermund, Wentura, and de Houwer (2005). This theory proposes that retrieval reactivates the prime response which interferes with selection of the correct probe response, thereby producing NP. 20 participants responded to pairs of red and blue digits, contingent on the identity of the digit presented in the target color. Behavioral NP involved RT increase by 16 ms. With shift trials (different hands used for prime and probe responses), in the DT condition LRP onset was delayed relative to control. By contrast, earlier LRP onset was observed for DT relative to control with no-shift trials (same hand used for prime and probe responses). Behavioral NP effects showed similar magnitude for shift and no-shift trials. Results support the Rothermund et al. (2005) theory of prime-response retrieval.     

基于客体的一致性效应的产生机制

采用具有不同深度信息的剪影和图片刺激为材料,要求被试完成形状判断任务,探究基于客体的一致性效应的产生机制。实验1中客体刺激呈现于屏幕中央位置;实验2进一步增强了刺激空间呈现的左右位置倾向;实验3则通过交叉手的范式分离了反应位置和反应手不同的编码对一致性效应的作用。结果发现:当刺激不存在显著的左右位置信息时,剪影刺激出现了一致性效应,图片则没有;而当刺激的空间位置信息显著时,剪影和图片均出现了一致性效应,这一效应在反应位置和反应手编码分离后仍然存在。因此得出结论:空间位置编码假说对解释基于客体的一致性效应的产生有重要作用。     

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.     

Priming of mental operations by masked stimuli

Motor responses can be affected by visual stimuli that have been made invisible by masking. Can masked visual stimuli also affect nonmotor operations that are necessary to perform the task? Here, I report priming effects of masked stimuli on operations that were cued by masking stimuli. Cues informed participants about operations that had to be executed with a forthcoming target stimulus. In five experiments, cues indicated (1) the required response, (2) part of the motor response, (3) the stimulus modality of the target stimulus, or (4) the task to be performed on a multidimensional stimulus. Motor and nonmotor priming effects followed comparable time courses, which differed from those of prime recognition. Experiment 5 demonstrated nonmotor priming without prime awareness. Results suggest that motor and nonmotor operations are similarly affected by masked stimuli.     

Masked response priming in expert typists

In masked priming tasks responses are usually faster when prime and target require identical rather than different responses. Previous research has extensively manipulated the nature and number of response-affording stimuli. However, little is known about the constraints of masked priming regarding the nature and number of response alternatives. The present study explored the limits of masked priming in a six-choice reaction time task, where responses from different fingers of both hands were required. We studied participants that were either experts for the type of response (skilled typists) or novices. Masked primes facilitated responding to targets that required the same response, responses with a different finger of the same hand, and with a homologous finger of the other hand. These effects were modulated by expertise. The results show that masked primes facilitate responding especially for experts in the S–R mapping and with increasing similarity of primed and required response.