Biomedical subjects

Jay Pratt

Publications and source records attributed to Jay Pratt.

At least 19 recordsLinked to original sources

PubMed2006

Objects do not aid inhibition of return in crossing the vertical meridian.

Location-based cuing experiments have shown that inhibition of return (IOR) spreads beyond a cued location but appears to be confined to the cued hemifield by the vertical meridian. Previous studies have also shown that IOR can spread across objects and here we investigate whether an object can be used to mediate the spreading of IOR into the opposite hemifield. Two experiments used a rectangular object that surrounded four target locations, two to the left and right of a central fixation point. The spreading of IOR in the presence of the object was determined and compared with a condition where the object-frame was absent. Object-present and object-absent trials were either mixed within a block (Experiment 1) or divided into separate blocks (Experiment 2). Both experiments revealed robust inhibition in the cued but not the uncued hemifield, further demonstrating the hemifield-based spreading of IOR.

Attention↗

PubMed2006

Distinct mechanisms for planning keypress and reaching responses: a developmental study.

This study examined developmental effects in the ability to use precue information for the planning of keypress and reaching responses. Participants from four age groups (7, 9, 13, and 21 year olds) performed a spatial precuing task either by pressing one of four response keys (keypress task) or by reaching directly toward one of the four target locations on the screen (reaching task). Reaction time data revealed striking age differences in the ability to use advance information in the keypress task, not in the reaching task. This dissociation confirms the hypothesis that distinct and separate mechanisms govern the planning of indirect keypress and direct reaching responses.

Adolescent↗

PubMed2006

Rapid onset and long-term inhibition of return in the multiple cuing paradigm.

Inhibition of return (IOR) refers to the finding that targets at cued locations are responded to more slowly than targets at uncued locations when a relatively long temporal interval occurs between the two events. In studies which have examined the time course of IOR (e.g., Samuel & Kat in Psychonomic Bulletin & Review, 10, 897-906, 2003), the effect is generally shown to develop at around 200 ms and dissipate at around 3,000 ms following a cue. A number of recent studies, however, have demonstrated that IOR can develop much more quickly (up to 50 ms following a cue) and last much longer (up to 13 min following a cue) in certain tasks. The present study uses the multiple cuing paradigm to determine whether IOR can be observed outside the normally reported temporal boundaries (300-3,000 ms) when attention is shifted very quickly (every 15 ms) or very slowly (every 1,500 ms) throughout the visual field. IOR was observed as quickly as 30 ms following cue onset and as long as 6,000 ms following cue onset. Implications for the role of IOR in visual search are discussed.

Cues↗

PubMed2006

Inhibition of return in cue-target and target-target tasks.

Inhibition of return (IOR), the term given for the slowing of a response to a target that appeared at the same location as a previously presented stimulus, has been studied with both target-target (TT; participants respond to each successive event) and cue-target (CT; participants only respond to the second of two events) tasks. Although both tasks have been used to examine the processes and characteristics of IOR, few studies have been conducted to understand if there are any differences in the processes that underlie the IOR that results from ignoring (CT paradigm) or responding to (TT paradigm) the first stimulus. The purpose of the present study was to examine the notion that IOR found in TT tasks represents "true" IOR whereas IOR found in CT tasks consist of both "true" IOR and response inhibition (Coward et al. in Exp Brain Res 155:124-128, 2004). Consistent with the pattern of effects found by Coward et al. (Exp Brain Res 155:124-128, 2004), IOR was larger in the CT task than in the TT task when a single detection response was required (Experiment 1). However, when participants completed one of two spatially-directed responses (rapid aiming movement to the location of the target stimulus), IOR effects from the CT and TT tasks were equal in magnitude (Experiment 2). Rather than CT tasks having an additional response inhibition component, these results suggest that TT tasks may show less of an inhibitory effect because of a facilitatory response repetition effect.

Adolescent↗

PubMed2006

Attentional modulation of the gap effect.

The gap effect refers to a reduction in the latency of saccades to peripherally appearing targets when the fixation point disappears a short time before target appearance. The effect has been attributed to a number of potential mechanisms that function to assist in the maintenance of fixation. One such mechanism, attention, has been the focus of some disagreement in the literature regarding the gap effect. In the present study, we had subjects attend to a portion of a complex fixation stimulus. On some trials the attended portion was removed prior to onset of a saccade target whereas on other trials an unattended portion was removed. Subjects were faster to initiate saccades when the attended portion was removed, thus establishing a role of attention in the gap effect. The results have important implications for our understanding of eye movements and the gap effect.

Adolescent↗

PubMed2006

Object- and location-based inhibition of return in younger and older adults.

When a cued object moves to new spatial coordinates, inhibition of return (IOR) with younger adults is found at the original cued location (location-based IOR) and at the current location of the object (object-based IOR). Older adults, however, show only location-based IOR. To determine whether this pattern of results represents a general age-related deficit in object-based IOR, the authors used static displays in which the placeholders (i.e., objects) were either present (location-based IOR+object-based IOR) or absent (location-based IOR only). Both age groups showed location-based IOR, but the older adults failed to show object-based IOR, consistent with age-related differences in visual pathways.

Adult↗

PubMed2006

Long-term inhibition of return for spatial locations: evidence for a memory retrieval account.

It has generally been accepted that attention is inhibited from returning to previously attended locations, and that this inhibition of return (IOR) lasts just two or three seconds. Recently, Tipper, Grison, and Kessler (2003) showed that IOR can occur over much longer periods of time provided the inhibition is encoded with a context-rich event. Here we examine standard (i.e., typical time range) and long-term IOR within the same experimental paradigm as a means to compare their properties. Experiment 1 used the simple displays typical of cueing paradigms and revealed that both standard and long-term IOR can be obtained under such conditions. Experiment 2 showed that both standard and long-term IOR occurred when there was incongruence between the required response on the current trial and that stored in memory. Furthermore, IOR was not produced when there was incongruence between a target feature (colour) of the current trial and that stored in memory. These results are consistent with a memory retrieval account of IOR and suggest that the same inhibitory mechanism may underlie both standard and long-term IOR.

Adult↗

PubMed2006

Moving farther but faster: an exception to Fitts's law.

Fitts's law holds that movement time (MT) increases with longer distances. Here we report a violation of this law: When the target appears in a structured, linear display with placeholders indicating the possible target locations, MT to the most distant target is not longer than MT to the second most distant target, but rather tends to be shorter. Furthermore, the presence of placeholders attenuates the range effect that occurs in the absence of placeholders. These findings suggest that Fitts's law may be limited to egocentric visuomotor action, and that the visual control of hand movements may use allocentric, in addition to egocentric, spatial information.

Adult↗

PubMed2006

Growing older does not always mean moving slower: examining aging and the saccadic motor system.

Although humans typically move more slowly as they age, one exception may be the saccadic motor system. To fully determine whether the execution of saccades is affected by age, the authors examined detailed kinematics of vertical and horizontal saccades across a range of saccadic amplitudes (4 degrees, 8 degrees, and 12 degrees). Ten younger and 20 older adults participated in each experiment. Whereas in the 1st experiment, the authors assessed volitionally generated saccades, in the 2nd experiment, they evaluated reflexively generated saccades. The results of those experiments showed that the saccadic motor system is relatively impervious to the effects of aging; in fact, the differences between vertical and horizontal saccades were more evident than were differences between saccades produced by younger and older adults. The authors discuss possible reasons for that relative resistance to aging.

Adolescent↗

PubMed2006

The effects of memory load on the time course of inhibition of return.

Inhibition of return (IOR) refers to a processing disadvantage at a recently attended location. It is generally agreed that when elicited in a cue-target task, IOR will not be apparent until attention is disengaged from the originally cued location and returned to a neutral state. Here we test the hypothesis that when such disengagement is dependent on endogenous control, a secondary task that taxes working memory capacity should delay the appearance of IOR. Participants were given a six-item verbal working memory load prior to the peripheral cue in a cue-target detection task. Consistent with the hypothesis, the appearance of IOR was delayed on trials for which participants had to hold information in working memory. Converging evidence was derived from a second experiment in which the time course of IOR's appearance, when we added a central cue to exogenously remove attention from the peripheral cue, was unaffected by the memory load.

Attention↗

PubMed2005

The effect of previous trial type on inhibition of return.

Inhibition of return (IOR) refers to the finding that targets appearing at previously cued locations are more slowly responded to than targets appearing at previously uncued locations when a relatively long temporal interval occurs between the cue and target. This experiment was conducted to determine whether the magnitude of IOR is influenced by the type of preceding trial (cued or uncued) and/or the location of the cue/target on the previous trial. Although no effect of cue/target location is observed, there was a marked effect of previous trial type, as IOR was greater following an uncued trial relative to a cued trial. This effect was attributable to differences in the response time as a function of previous trial type: specifically, participants were faster to respond to cued and uncued trials when the previous trial type was identical.

Attention↗

PubMed2005

The effects of action video game experience on the time course of inhibition of return and the efficiency of visual search.

The ability to efficiently search the visual environment is a critical function of the visual system, and recent research has shown that experience playing action video games can influence visual selective attention. The present research examined the similarities and differences between video game players (VGPs) and non-video game players (NVGPs) in terms of the ability to inhibit attention from returning to previously attended locations, and the efficiency of visual search in easy and more demanding search environments. Both groups were equally good at inhibiting the return of attention to previously cued locations, although VGPs displayed overall faster reaction times to detect targets. VGPs also showed overall faster response time for easy and difficult visual search tasks compared to NVGPs, largely attributed to faster stimulus-response mapping. The findings suggest that relative to NVGPs, VGPs rely on similar types of visual processing strategies but possess faster stimulus-response mappings in visual attention tasks.

Adolescent↗

PubMed2005

Letter processing interferes with inhibition of return: evidence for cortical involvement.

Inhibition of return (IOR) refers to the finding that, when the time lag between a cue and a target is prolonged, the reaction to the target, when it eventually appears, is actually slower than with no cue. This phenomenon is thought to make visual search more efficient, and it is subserved by the left inferior parietal cortex and the supramarginal gyrus bilaterally. Interestingly, the very same brain structures are also involved in letter processing. Accordingly, we asked whether the two mental processes interfere with each other when simultaneously probed. The first experiment used a typical IOR procedure, but the cue/target placeholders were either simple geometric shapes or English letters. The results show that, although IOR is approximately the same across visual fields when shape placeholders are used, it is significantly lessened in the right visual field when letters are used as cue and target placeholders. To examine if this finding was due to potential spatial frequency differences between the placeholders, a second experiment using shapes and Japanese letters was conducted, and no differences in IOR were found. The supramarginal gyrus appears to be the most likely locus for the letter-IOR interference effect because it is active bilaterally in IOR, but only in the left hemisphere during letter processing. These findings provide support for the notion that IOR is not simply due to subcortical processes but also involves processing from cortical structures.

Analysis of Variance↗

PubMed2005

Pro-saccades and anti-saccades to onset and offset targets.

Pro- and anti-saccades made to either onset or offset targets were examined to determine which of (1) changes in luminance or (2) the appearance of new peripheral objects, is more important in the reflexive generation of pro-saccades. In two experiments, pro-saccades had faster reaction times than did anti-saccades, but the difference was much greater for onset targets than offset targets (both with white targets on black backgrounds and black targets on white backgrounds). These findings suggest that there is a continuum of "prepotentness" in the oculomotor system with new peripheral objects being especially effective in generating reflexive pro-saccades.

Adolescent↗

PubMed2005

Visual processing of targets can reduce saccadic latencies.

Normal human saccadic reaction times (SRTs) have been thought to be approximately 200 ms. The present study, using an experimental method that takes advantage of what the saccade system has evolved to do (by instructing subjects to rapidly acquire detailed visual information from the environment), shows that human SRTs are actually on the order of 150 ms. Moreover, when combined with the sensory-based "gap" effect (removal of gaze fixation object prior to target presentation), this method yielded extremely low SRTs. These findings imply that previous approximations of human SRTs may have been too conservative, and that the group of saccades often classified as "express" may instead represent the norm.

Adult↗

PubMed2005

Attending to eye movements and retinal eccentricity: evidence for the activity distribution model of attention reconsidered.

When testing between spotlight and activity distribution models of visual attention, D. LaBerge, R. L. Carlson, J. K. Williams, and B. G. Bunney (1997) used an experimental paradigm in which targets are embedded in 3 brief displays. This paradigm, however, may be confounded by retinal eccentricity effects and saccadic eye movements. When the retinal eccentricities of the targets are equated and eye position is monitored, the pattern of results reported by LaBerge et al., which supported the activity distribution model, is not found. This result underscores the importance of considering targets' eccentricity and people's inclination to make saccadic eye movements in certain types of visual cognition tasks. ((c) 2005 APA, all rights reserved).

Attention↗

PubMed2005

Examining task difficulty and the time course of inhibition of return: detecting perceptually degraded targets.

The ability to efficiently direct visual attention to salient features in the environment is a critical function of the visual system. The finding that people are slower to detect a target that appears at a previously cued location is thought to reflect a mechanism known as inhibition of return (IOR). Past research has shown that difficult target discriminations result in a greater amount of time needed to inhibit previously attended locations (i.e., a delayed onset of inhibition), suggesting that task difficulty plays a critical role in the allocation of attention. In this study, IOR was measured at a wide range of SOAs while participants detected either a perceptually degraded target or a standard, high luminance target. When responses were made to a perceptually degraded target, the time course of IOR was delayed by approximately 250 ms (relative to the control group), suggesting that the difficulty in detecting targets also influences the allocation of attention. The results are consistent with the notion that IOR is not simply a reflexive subcortical mechanism but rather involves top-down attentional control settings.

Adult↗

PubMed2005

Looking for inhibition of return in pigeons.

We conducted four experiments in order to investigate whether pigeons' responses to a recently attended (i.e., recently pecked) location are inhibited. In Experiments 1 and 2, stimulus displays were similar to those used in studies of inhibition of return (IOR) with humans; responses to cued targets tended to be facilitated rather than inhibited. In Experiments 3 and 4, birds were presented with stimulus displays that mimicked clusters of small grains and were relatively localized, which should have been more appropriate for detecting IOR in pigeons. The results from these experiments again provided evidence for facilitation of responding to cued targets, rather than for IOR.

Animals↗