The timecourse of space- and object-based attentional prioritization with varying degrees of certainty

Attention and platypuses

This perspective piece discusses a set of attentional phenomena that are not easily accommodated within current theories of attentional selection. We call these phenomena attentional platypuses, as they allude to an observation that within biological taxonomies the platypus does not fit into either mammal or bird categories. Similarly, attentional phenomena that do not fit neatly within current attentional models suggest that current models are in need of a revision. We list a few instances of the "attentional platypuses" and then offer a new approach, that we term dynamically weighted prioritization, stipulating that multiple factors impinge onto the attentional priority map, each with a corresponding weight. The interaction between factors and their corresponding weights determines the current state of the priority map which subsequently constrains/guides attentional allocation. We propose that this new approach should be considered as a supplement to existing models of attention, especially those that emphasize categorical organizations. This article is categorized under: Psychology > Attention Psychology > Perception and Psychophysics Neuroscience > Cognition.

EXPRESS: Contextual uncertainty of visual scene modulates object-based attention

Contextual information involves invariant properties that are critical in selective attention. There is no direct evidence showing the effect of contextual information on object-based selective attention. The current study aimed to investigate the role of contextual uncertainty on object-based effect using a flanker task and to clarify the contradictory results obtained in previous studies. Herein, contextual uncertainty specifically referred to the configurations of the stimuli presented randomly as vertical or horizontal displays (high contextual uncertainty) that was reduced by showing consistent configurations within a block, via implicit learning of configuration (low contextual uncertainty). In Experiment 1, the object-based effect was observed under the high uncertainty condition and disappeared under the low uncertainty condition, demonstrating that contextual uncertainty modulated object-based attention. Experiment 2 provided explicit knowledge of the configural orientations, which can be utilised to sufficiently guide subsequent perception with increase in cueing interval, and therefore, affected contextual uncertainty. Relative to a short cueing interval, the long cueing interval enabled the participants to utilise the contextual knowledge for guiding visual attention and reducing uncertainty. Consistent with the finding in Experiment 1, the explicit manipulation of contextual uncertainty affected the object-based effect. The results proved that contextual uncertainty played an important role in prioritisation in object-based attentional selection. The mechanism of the interplay between contextual uncertainty and object-based attention was discussed.

Target frequency modulates object-based attention

Decades of research have provided evidence that object representations contribute to attentional selection. However, most evidence for object-based attentional allocation is drawn from studies employing the two-rectangle paradigm where the target distribution is biased towards the cued object. It is thus unclear whether object-based attentional selection is from object representations or a consequence of spatial attention based on statistical imbalances. Here, we investigate the extent to which target frequency modulates object-based attention by systematically manipulating the frequency of target appearance in a particular spatial location within objects to equate spatial allocation, bias specific spatial locations, or bias objects. In four experiments, participants were presented with a variant of the two-rectangle paradigm in which one end of a rectangle was cued and performed a target discrimination task. Critically, the target location probabilities were parametrically manipulated. The target could appear equally in all ends within the objects (valid, invalid within-object, invalid between-object, diagonal) (Experiment 1) or with overall equality between objects but biased towards the invalid locations (Experiment 2). The target could also appear in three locations (valid, invalid within-object, invalid between-object) distributed equally between objects but biased towards the invalid between-object location (Experiment 3) or with an overall bias towards the invalid between-object location (Experiment 4). We observed that while objects bias attention, spatial biases are prioritized over object representations. Combined results suggest that object-based contribution to attentional guidance is the result of both spatial probabilities and object representations.

Attention scales according to inferred real-world object size

Natural scenes consist of objects of varying shapes and sizes. The impact of object size on visual perception has been well-demonstrated, from classic mental imagery experiments¹, to recent studies of object representations reporting topographic organization of object size in the occipito-temporal cortex². While the role of real-world physical size in perception is clear, the effect of inferred size on attentional selection is ill-defined. Here, we investigate whether inferred real-world object size influences attentional allocation. Across five experiments, attentional allocation was measured in objects of equal retinal size, but varied in inferred real-world size (for example, domino, bulldozer). Following each experiment, participants rated the real-world size of each object. We hypothesized that, if inferred real-world size influences attention, selection in retinal size-matched objects should be less efficient in larger objects. This effect should increase with greater attentional demand. Predictions were supported by faster identified targets in objects inferred to be small than large, with costlier attentional shifting in large than small objects when attentional demand was high. Critically, there was a direct correlation between the rated size of individual objects and response times (and shifting costs). Finally, systematic degradation of size inference proportionally reduced object size effect. It is concluded that, along with retinal size, inferred real-world object size parametrically modulates attention. These findings have important implications for models of attentional control and invite sensitivity to object size for future studies that use real-world images in psychological research.

Object width modulates object-based attentional selection

Visual input typically includes a myriad of objects, some of which are selected for further processing. While these objects vary in shape and size, most evidence supporting object-based guidance of attention is drawn from paradigms employing two identical objects. Importantly, object size is a readily perceived stimulus dimension, and whether it modulates the distribution of attention remains an open question. Across four experiments, the size of the objects in the display was manipulated in a modified version of the two-rectangle paradigm. In Experiment 1, two identical parallel rectangles of two sizes (thin or thick) were presented. Experiments 2-4 employed identical trapezoids (each having a thin and thick end), inverted in orientation. In the experiments, one end of an object was cued and participants performed either a T/L discrimination or a simple target-detection task. Combined results show that, in addition to the standard object-based attentional advantage, there was a further attentional benefit for processing information contained in the thick versus thin end of objects. Additionally, eye-tracking measures demonstrated increased saccade precision towards thick object ends, suggesting that Fitts's Law may play a role in object-based attentional shifts. Taken together, these results suggest that object-based attentional selection is modulated by object width.

Coherence of visual representations: attention and integration of contour shape information

Change blindness demonstrations illustrate the limited detail of visual representations. These demonstrations typically require disruption to the visual input when the change occurs or changes that occur very slowly. With sustained viewing or faster changes to the scenes, changes are more easily detected because attention can be effectively allocated to the part of the scene that is changing. Here, we investigate the interaction of visual attention and memory in the domain of 2-D contour shapes. We show, using a novel combination of established change blindness paradigms, that changes can go unnoticed even when they occur on isolated 2-D contour shapes. The effect appears to be due to involuntary updating of stored shape information. This involuntary updating process, however, is constrained so that previously attended shape information is updated only when attention is reallocated to qualitatively similar shape information.