The role of attention in the affordance effect: can we afford to ignore it?

Size coding of alternative responses is sufficient to induce a potentiation effect with manipulable objects

The mere perception of manipulable objects usually grasped with a power-grip (e.g., an apple) or a precision-grip (e.g., a cherry) potentiate power-grip- and precision-grip-responses, respectively. This effect is seen as to be driven by automatic access of the representation of manipulable objects that includes a motor representation of usually performed grasping behaviors (i.e., the embodied view). Nevertheless, a competing account argues that this effect could be due to an overlapping of size codes used to represent both manipulable objects and response options. Indeed, objects usually grasped with a power- and a precision-grip (e.g., an apple vs. a cherry) could be coded as large- and small-objects, respectively; and power- and precision-grip responses as large- and small-responses, respectively. We conducted 4 experiments to test this hypothesis. In Experiment 1, the response device usually used in studies reporting a potentiation effect is fixed horizontally (the grasping component of responses was removed). We instructed participants to press the small-switch with their index-digit and the large-switch with their palm-hand. In line with the size-coding-hypothesis, responses on the small-switch performed with the index-digit led to shorter RTs when objects usually associated with a precision-grip (e.g., a cherry) were presented compared to objects usually associated with a power-grip (e.g., an apple). A reverse pattern was obtained for responses on the large-switch performed with the palm-hand. In Experiments 2, 3 and 4, we went further by investigating which factors of Experiment 1 allow the size coding of responses: the size of switch and/or the size of the effector part used. Data confirmed the critical involvement of the size of switches and the possible involvement of the size of the effector part used. Thus, data support the possibility that the potentiation of grasping is due to a compatibility/incompatibility between size codes rather than involving motor representations of usually performed grasping behaviors as advocated in several embodied views. Moreover, data support the possibility that responses are coded thanks to a size code that extends the Theory of Event Coding.

Exploring the Role of Action Consequences in the Handle-Response Compatibility Effect

Previous research investigating handle-response compatibility effects with graspable objects used different categories of objects as stimuli, regardless of their specific, intrinsic characteristics. The current study explores whether different types of objects' characteristics may elicit different types of spatial compatibility, that is, handle-response and response-effect compatibility as well as their potential interaction. In Experiment 1, objects having a graspable handle opposite to either a visible functional component (i.e., handle-function objects: a teapot) or a latent functional component (handle-only objects: a pitcher lacking the spout) were presented separately in different blocks. Both the handle and the goal-directed functional components of these objects were located on the horizontal axis. In Experiment 2, handle-only objects had a handle located on the horizontal axis and a latent functional component located on the vertical axis (e.g., a cup). In both experiments, participants were required to judge the material (plastic and metal) the object was made of. Results showed that the handle-response compatibility effect was sensitive to whether the actions consequences of object manipulation took place on the horizontal rather than on the vertical axis.

A meta-analysis of the object-based compatibility effect

The object-based compatibility effect (CE) describes, in the context of two-choice keypress tasks, the facilitation of response times (RTs) by the correspondence between participants' response hand and the task-irrelevant orientation of a viewed object's handle. Object-based CEs are often attributed to affordance perception. Although the object-based CE paradigm is the major RT task used to study affordances, failures to replicate the effect have raised questions about its robustness. Moreover, it remains unclear whether the object-based CE is indeed indicative of affordances, or whether it is merely an example of spatial CEs brought about by the object's protruding handle. We present a meta-analysis of object-based CEs to (1) obtain a point estimate of the overall effect and (2) test for moderation consistent with either affordance or spatial compatibility accounts. From 88 independent effects (computed on 2359 participants), we estimated a small but significant compatibility effect (ES = 0.106, z = 5.44, p < .001 95% CI:[0.068, 0.145]), although evidence of publication bias suggests that the true effect is smaller in magnitude. Further, we found significant heterogeneity in effect sizes, indicating between-study variation beyond sampling variability. Moderator analyses indicated that CEs were larger when (1) task-relevant decisions were not about the function of objects, (2) when stimuli were silhouettes as opposed to photographs, and (3) when objects were centered on-screen according to their base or pixel distribution. Response mode (within vs between-hand) did not moderate CEs, nor did the critical interaction between stimulus type (photograph vs silhouette/illustration) and response mode. In all, results are mostly consistent with a spatial compatibility account of object-based CEs. Finally, analyses revealed moderation by trial and task structure, providing implications for study design.

Motor (but not auditory) attention affects syntactic choice

Understanding the determinants of syntactic choice in sentence production is a salient topic in psycholinguistics. Existing evidence suggests that syntactic choice results from an interplay between linguistic and non-linguistic factors, and a speaker’s attention to the elements of a described event represents one such factor. Whereas multimodal accounts of attention suggest a role for different modalities in this process, existing studies examining attention effects in syntactic choice are primarily based on visual cueing paradigms. Hence, it remains unclear whether attentional effects on syntactic choice are limited to the visual modality or are indeed more general. This issue is addressed by the current study. Native English participants viewed and described line drawings of simple transitive events while their attention was directed to the location of the agent or the patient of the depicted event by means of either an auditory (monaural beep) or a motor (unilateral key press) lateral cue. Our results show an effect of cue location, with participants producing more passive-voice descriptions in the patient-cued conditions. Crucially, this cue location effect emerged in the motor-cue but not (or substantially less so) in the auditory-cue condition, as confirmed by a reliable interaction between cue location (agent vs. patient) and cue type (auditory vs. motor). Our data suggest that attentional effects on the speaker’s syntactic choices are modality-specific and limited to the visual and motor, but not the auditory, domain.

Spatial stimulus-response compatibility and affordance effects are not ruled by the same mechanisms

Stimulus position is coded even if it is task-irrelevant, leading to faster response times when the stimulus and the response locations are compatible (spatial Stimulus–Response Compatibility–spatial SRC). Faster responses are also found when the handle of a visual object and the response hand are located on the same side; this is known as affordance effect (AE). Two contrasting accounts for AE have been classically proposed. One is focused on the recruitment of appropriate grasping actions on the object handle, and the other on the asymmetry in the object shape, which in turn would cause a handle-hand correspondence effect (CE). In order to disentangle these two accounts, we investigated the possible transfer of practice in a spatial SRC task executed with a S–R incompatible mapping to a subsequent affordance task in which objects with either their intact handle or a broken one were used. The idea was that using objects with broken handles should prevent the recruitment of motor information relative to object grasping, whereas practice transfer should prevent object asymmetry in driving handle-hand CE. A total of three experiments were carried out. In Experiment 1 participants underwent an affordance task in which common graspable objects with their intact or broken handle were used. In Experiments 2 and 3, the affordance task was preceded by a spatial SRC task in which an incompatible S–R mapping was used. Inter-task delays of 5 or 30 min were employed to assess the duration of transfer effect. In Experiment 2 objects with their intact handle were presented, whereas in Experiment 3 the same objects had their handle broken. Although objects with intact and broken handles elicited a handle-hand CE in Experiment 1, practice transfer from an incompatible spatial SRC to the affordance task was found in Experiment 3 (broken-handle objects), but not in Experiment 2 (intact-handle objects). Overall, this pattern of results indicate that both object asymmetry and the activation of motor information contribute to the generation of the handle-hand CE effect, and that the handle AE cannot be reduced to a SRC effect.

Dissociating between object affordances and spatial compatibility effects using early response components

Perception and action are tightly linked: objects may be perceived not only in terms of visual features, but also in terms of possibilities for action. Previous studies showed that when a centrally located object has a salient graspable feature (e.g., a handle), it facilitates motor responses corresponding with the feature's position. However, such so-called affordance effects have been criticized as resulting from spatial compatibility effects, due to the visual asymmetry created by the graspable feature, irrespective of any affordances. In order to dissociate between affordance and spatial compatibility effects, we asked participants to perform a simple reaction-time task to typically graspable and non-graspable objects with similar visual features (e.g., lollipop and stop sign). Responses were measured using either electromyography (EMG) on proximal arm muscles during reaching-like movements, or with finger key-presses. In both EMG and button press measurements, participants responded faster when the object was either presented in the same location as the responding hand, or was affordable, resulting in significant and independent spatial compatibility and affordance effects, but no interaction. Furthermore, while the spatial compatibility effect was present from the earliest stages of movement preparation and throughout the different stages of movement execution, the affordance effect was restricted to the early stages of movement execution. Finally, we tested a small group of unilateral arm amputees using EMG, and found residual spatial compatibility but no affordance, suggesting that spatial compatibility effects do not necessarily rely on individuals' available affordances. Our results show dissociation between affordance and spatial compatibility effects, and suggest that rather than evoking the specific motor action most suitable for interaction with the viewed object, graspable objects prompt the motor system in a general, body-part independent fashion.