The role of executive control in the activation of manual affordances

Critical bottom-up attentional factors in the handle orientation effect: asymmetric luminance transients and object-center eccentricity relative to fixation

In 1998, Tucker and Ellis found that keypress responses are faster when the task-irrelevant orientation of a graspable object's handle corresponds to response hand location. Over the past 20 years, researchers have disagreed over the extent to which grasping affordance or spatial compatibility contributes to the effect. One of the causes behind the conflicting findings and interpretations may be that studies advocating the grasping affordance view have tended to overlook the contributions of low-level perceptual characteristics to the observed correspondence effects. The present study evaluated the role of visual salience and bottom-up attention in the occurrence of the effect. Experiment 1 involved a vertical orientation task (bimanual keypresses) using photographs of graspable objects, centered based on object width or pixel area. The same procedure was performed using a color discrimination task on solid-colored silhouettes, large (Experiment 2) and small-sized (Experiment 3), as well as silhouette outlines (Experiment 4). Similar result patterns across Experiments 1-3 were observed and discussed in the context of diverging findings in Experiment 4, prompting us to introduce the notion of asymmetry-based Simon effects, whereby location is coded at stimulus onset on the basis of asymmetric changes in luminance between both hemifields, coupled with object-center eccentricity relative to fixation. These low-level factors were critical in modulating the temporal dynamics, as well as the direction of compatibility effects (toward handles or bodies), irrespective of grasping affordance, task, object identity, or stimulus size. The present findings provide further evidence that the Tucker and Ellis paradigm for studying variable affordances is extremely vulnerable to location-coding, which may arise on the basis of exogenous deployments of attention. This problem is only exacerbated in a large portion of the relevant literature, whereby visually complex stimuli are primarily discussed in terms of their graspable nature and relation to task, rather than their low-level, attention-capturing features.

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.

Information presentation compatibility in a simple digital control panel design: eye-tracking study

Various designs of typical digital control panels were analyzed experimentally from both the effectiveness and efficiency points of view. Subjects performed information comparison tasks aimed at keeping vehicle velocity at the same level. The experiment involved two versions of speedometers for displaying current and target velocities (clock-face and digital). The stimuli were also differentiated by the target velocity value (20, 50 and 80 km/h) and the correct response type (increase or decrease). Subjects' performance results along with the eye-tracking data were qualitatively and quantitatively analyzed for all 24 experimental conditions.