Oculocentric coding of inhibited eye movements to recently attended locations

Results are reported for experiments that examined eye movements directed toward recently cued objects. In 1 experiment participants were slower to initiate saccades toward the earlier location of an object that had been cued, even though the cued object had subsequently moved away from that location. Other experiments involved exploring the reference frame within which the inhibited eye movements are encoded. These experiments revealed that the eye movement that is inhibited is encoded in an oculocentric-rather than an environmental-reference frame. However, simple detection as indexed by manual keypress responses is encoded in an environmental reference frame. The results have implications for inhibition of return, for the link between eye movements and attention, and for the nature of the spatial reference frames in which both covert and overt movements of attention are encoded.     

A new estimation of the duration of attentional dwell time

How rapidly can attention move from one object to the next? Previous studies in which the dwell time paradigm was used have estimated attentional switch times of 200–500 msec, results incompatible with the search rate estimates of 25–50 msec shown in numerous visual search studies. It has been argued that dwell times are so long in the dwell time paradigm because the attentional shifts measured are unlike those used in visual search. In the present experiment, a variation of a visual search task was used, in which serial endogenous (volitional) deployments of attention were measured directly by means of a probe reaction time task. The experiment revealed a dwell time of about 250 msec, consistent with the faster estimates from other dwell time studies. This result suggests that endogenous shifts of attention may be relatively slow and that the faster attentional shifts estimated from visual search tasks may be due to the involvement of bottom-up processes.     

The planning and execution of sequential eye movements: saccades do not show the one target advantage

The present experiment examined the one-target advantage (OTA) with regard to saccadic eye movements. The OTA, previously found with manual pointing responses, refers to the finding that movements are executed faster when the limb is allowed to stop on the target compared to the situation where it has to proceed and hit a second target. Using an adapted limb movement OTA task, saccades of 5 degrees and 15 degrees were made to (a) a single target (one-target), (b) one target and immediately to another target without a change in direction (two-target-extension), and (c) one target and immediately back to the start location (two-target-reversal). Unlike manual movements, the movement times for the initial saccade in the two-target-extension condition were not prolonged compared to either of the other two conditions. Moreover, this pattern of results was found for both the shorter and longer amplitude saccades. The results indicate that the OTA does not occur in the oculomotor system and therefore is not a general motor control phenomenon.     

Symbolic control of visual attention: The role of working memory and attentional control settings

This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. ((c) 2003 APA, all rights reserved)     

The spatial distribution of inhibition of return

Inhibition of return (IOR) refers to the finding that response times (RTs) are typically slower for targets at previously attended (cued) locations than for targets at novel (uncued) locations. Although previous research has indicated that IOR may spread beyond a cued location, the present study is the first to examine the spatial distribution of IOR with high spatial resolution over a large portion of the central visual field. This was done by using a typical IOR procedure (cue, delay, target) with 4 cue locations and 441 target locations (each separated by 1° of visual angle). The results indicate that IOR spreads beyond the cued location to affect the cued hemifield. However, the cues also produced a gradient of RTs throughout the visual field, with inhibition in the cued hemifield gradually giving way to facilitation in the hemifield opposite the cue.     

The Effect of Inhibition of Return on Lexical Access

Abstract—Inhibition of return refers to a bias against returning attention to a location or object that has been recently attended. Recent research has shown that inhibition of return can be found not only in simple detection tasks, but also in tasks requiring relatively simple discrimination judgments. The present experiments examined whether inhibition of return occurs in tasks that require complex discriminations such as lexical decision and categorization tasks. Not only was inhibition of return found in both experiments, but a greater amount of inhibition was found for low-frequency words than for high-frequency words. These findings suggest that inhibition of return not only inhibits returning attention to previously attended locations, but can also affect the processing that is required for lexical access.