Amelia R. Hunt

Inhibition of return: Dissociating attentional and oculomotor components.

Inhibition of return (IOR) describes a performance decrement for stimuli appearing at recently cued locations. Both attentional and motor processes have been implicated in the IOR effect. The present data reveal a double dissociation between the attentional and motor components of IOR whereby the motor-based component of IOR is present when the response is oculomotor, and the attention-based component of IOR is present when the response is manual. These 2 distinct components should be considered and studied separately, as well as in relation to each other, if a comprehensive theory of IOR is to be achieved. ((c) 2003 APA, all rights reserved)

Looking ahead: The perceived direction of gaze shifts before the eyes move

How do we know where we are looking? Our direction of gaze is commonly thought to be assigned to the location in the world that falls on our fovea, but this may not always hold, especially, as we report here, just before an eye movement. Observers shifted their gaze to a clock with a fast-moving hand and reported the time perceived to be on the clock when their eyes first landed. The reported time was 39 ms earlier than the actual time the eyes arrived. In a control condition, the clock moved to the eyes, mimicking the retinal motion but without the eye movement. Here the reported time lagged 27 ms behind the actual time on the clock when it arrived. The timing of perceived fixation in our experiment is similar to that for the predictive activation observed in visual cortex neurons at the time of eye movements.

The Time Course of Attentional and Oculomotor Capture Reveals a Common Cause.

Eye movements are often misdirected toward a distractor when it appears abruptly, an effect known as oculomotor capture. Fundamental differences between eye movements and attention have led to questions about the relationship of oculomotor capture to the more general effect of sudden onsets on performance, known as attentional capture. This study explores that issue by examining the time course of eye movements and manual localization responses to targets in the presence of sudden-onset distractors. The results demonstrate that for both response types, the proportion of trials on which responses are erroneously directed to sudden onsets reflects the quality of information about the visual display at a given point in time. Oculomotor capture appears to be a specific instance of a more general attentional capture effect. Differences and similarities between the two types of capture can be explained by the critical idea that the quality of information about a visual display changes over time and that different response systems tend to access this information at different moments in time.

Orienting Attention in Aging and Parkinson's Disease: Distinguishing Modes of Control

Past research on attentional orienting and Parkinsons disease (PD) has been compromised because the experimental paradigms tended to confound different forms of orienting. We sought to overcome this by examining the attentional orienting of three distinct groups (PD-patients, age-matched controls, and young controls) on five different tasks, four of which isolated pure forms of orienting. On two covert orienting tasks PD patients oriented volitional (Experiment 1) and reflexive (Experiment 2) covert attention in a healthy and normal manner for their age. On two overt orienting tasks, PD patients were found to execute volitional eye movements that were prone to undershoot their target goal (Experiment 3), and reflexive eye movements that were unusually fast (Experiment 4). When required to perform an antisaccade task (Experiment 5), which combines reflexive and volitional modes of overt orienting, PD patients performed normally This indicates that using a task which combines different modes of orienting creates a situation that is more than the sum of its parts. Together our study supports the thesis that it is crucial to isolate and investigate different modes of attentional control.

Eliminating the cost of task set reconfiguration

With insufficient time to fully prepare for a switch in task, a deterioration in performance on the first trial of a new task would be expected. The interest of researchers has been captured by the residual switch costs that, surprisingly, remain despite sufficient time to prepare.We used a very simple task to investigate the costs to reaction time and accuracy associated with changing between two different instructional sets every eight trials. Subjects responded to left and right visual targets by making either spatially compatible or incompatible eye movements (Experiment 1) or buttonpress responses (Experiment 2). The subjectswere cued as to whether tomake the compatible or the incompatible response by the color of a border appearing on the perimeter of the display. In cases in which the subject alternated betweenmaking pro- and antisaccades,the large costs to reaction time and accuracy at the short cue—target stimulus onset asynchrony were completely eliminated when sufficient time was provided to prepare for the switch. This complete elimination of residual switch costs was not obtained when the same alternationwas applied to manual responses. This pattern of results links residual costs to response selectionprocesses and suggests that they are not a necessarycomponent of the switch process. We propose that the elimination of “stubborn” residual switch costs is rooted in our use of ahyper-compatible task (making saccadestoward targets) that placesminimal demands on response selection.

Remapped visual masking

Cells in saccade control areas respond if a saccade is about to bring a target into their receptive fields (J. R. Duhamel, C. L. Colby, & M. R. Goldberg, 1992). This remapping process should shift the retinal location from which attention selects target information (P. Cavanagh, A. R. Hunt, S. R. Afraz, & M. Rolfs, 2010). We examined this attention shift in a masking experiment where target and mask were presented just before an eye movement. In a control condition with no eye movement, masks interfered with target identification only when they spatially overlapped. Just before a saccade, however, a mask overlapping the target had less effect, whereas a mask placed in the targets remapped location was quite effective. The remapped location is the retinal position the target will have after the upcoming saccade, which corresponds to neither the retinotopic nor spatiotopic location of the target before the saccade. Both effects are consistent with a pre-saccadic shift in the location from which attention selects target information. In the case of retinally aligned target and mask, the shift of attention away from the target location reduces masking, but when the mask appears at the targets remapped location, attentions shift to that location brings in mask information that interferes with the target identification.

The effect of emotional faces on eye movements and attention

The present study investigated the nature of attention to facial expressions using an oculomotor capture paradigm. Participants were required to make a speeded saccade toward a predefined target and ignore distractors. The valence (happy or angry) and orientation (upright or inverted) of the target and distractors varied. We found evidence that irrelevant happy and angry face distractors did capture attention, but only when emotions were the target of search. Eye movements were not directed toward angry distractors any more often than toward happy distractors, and saccades to angry face targets were no faster than to other targets. The results provide evidence that emotion information can be used as a feature to voluntarily select targets and direct attention, suggesting attention is not necessary for the identification of emotional expression. There was no evidence, however, that angry face stimuli have a special priority for reflexively orienting attention.

Multisensory executive functioning.

To better understand the prefrontal circuitry that putatively supports executive functions, such as those involved in switching tasks, we asked whether a current task set is open equally to receiving information from any sensory modality or if it is to some degree modality-specific. Subjects were presented with a sequence of digits to be classified as either odd/even or greater/less than five. The digits were either auditory or visual, with the modality varying randomly. Results demonstrated a reaction time (RT) cost associated with switching between tasks and also an unexpected cost of switching between modalities. When both modality and task switched, the two costs were greater than either of the costs alone, but significantly less than predicted simply by summing the two costs together (i.e., they were underadditive). These data indicate that the frontal mechanisms that allow for a switch in task are only partially modality-specific. Current theories of executive function must be adapted to account for this finding. We also suggest that the present paradigm is amenable to future research aimed at determining precisely how modalities are linked within a task set.

Representations in Visual Cognition It’s About Time

Visual cognition relies on changing representations of visual information. The dynamic nature of representations is demonstrated by new findings in human perception and attention showing that the influence of specific aspects of a stimulus on behavior changes dramatically over time. As a consequence, performance depends on what point in time responses are measured. Specifically, quick responses to early representations of a new scene are heavily influenced by the relative salience of different stimuli in the visual field. Slow responses based on later representations of the same scene are informed by more complex information that integrates prior knowledge and observer goals. Thus, as a result of the dynamic nature of representations, the kind of information that is prioritized depends on the moment in time the representation is accessed. Examining how representations change over time can lead to new and important insights in a wide range of domains of human cognition.

Saccadic eye movements and perceptual judgments reveal a shared visual representation that is increasingly accurate over time

Although there is evidence to suggest visual illusions affect perceptual judgments more than actions, many studies have failed to detect task-dependant dissociations. In two experiments we attempt to resolve the contradiction by exploring the time-course of visual illusion effects on both saccadic eye movements and perceptual judgments, using the Judd illusion. The results showed that, regardless of whether a saccadic response or a perceptual judgement was made, the illusory bias was larger when responses were based on less information, that is, when saccadic latencies were short, or display duration was brief. The time-course of the effect was similar for both the saccadic responses and perceptual judgements, suggesting that both modes may be driven by a shared visual representation. Changes in the strength of the illusion over time also highlight the importance of controlling for the latency of different response systems when evaluating possible dissociations between them.