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Biomedical subjects

Jan Theeuwes

Publications and source records attributed to Jan Theeuwes.

At least 19 recordsLinked to original sources
PubMed2004

Endogenous and exogenous attention shifts are mediated by the same large-scale neural network.

Event-related fMRI was used to examine the neural basis of endogenous (top-down) and exogenous (bottom-up) spatial orienting. Shifts of attention were induced by central (endogenous) or peripheral (exogenous) cues. Reaction times on subsequently presented targets showed the expected pattern of facilitation and inhibition in both conditions. No difference in brain activity was observed when the two orienting conditions were contrasted with a liberal threshold, showing that both forms of orienting were mediated by the same neural network. Compared to within-block control trials, both endogenous and exogenous orienting activated a fronto-parietal network consisting of premotor cortex, posterior parietal cortex, medial frontal cortex and right inferior frontal cortex. Within these regions, equally strong activation was observed for both orienting conditions. It is concluded that endogenous and exogenous orienting are mediated by the same large-scale network of frontal and parietal brain areas.

Adult↗
PubMed2004

Inhibition-of-return and oculomotor interference.

The present study shows that inhibition-of-return reduces competition for selection within the oculomotor system. We examined the effect of a distractor when it was presented at an inhibited location (IOR). The results show that due to IOR distractors cause less interference. This was evident in all three measures. First, there was less oculomotor capture when a distractor was presented at an inhibited location. Second, the saccade latency to the target was shorter when a distractor appeared at an inhibited location than when it appeared at a non-inhibited location. Third, there was less curvature towards the distractor when it was presented at inhibited location relative to a non-inhibited location. The observation that there is less interference for a distractor presented at an inhibited location suggests that IOR reduces the exogenous activation of the distractor within the saccade map.

Attention↗
PubMed2004

Response selection in visual search: the influence of response compatibility of nontargets.

The authors used visual search tasks in which components of the classic flanker task (B. A. Eriksen & C. W. Eriksen, 1974) were introduced. In several experiments the authors obtained evidence of parallel search for a target among distractor elements. Therefore, 2-stage models of visual search predict no effect of the identity of those distractors. However, clear compatibility effects of the distractors were obtained: Responses were faster when the distractors were compatible with the response than when they were incompatible. These results show that even in parallel search tasks identity information is extracted from the distractors. In addition, alternative interpretations of the results in terms of the occasional identification of a distractor before or after the target was identified could be ruled out. The results showed that flat search slopes obtained in visual search experiments provide no benchmark for preattentive processing.

Attention↗
PubMed2004

The relationship between inhibition of return and saccade trajectory deviations.

After presentation of a peripheral cue, a subsequent saccade to the cued location is delayed (inhibition of return: IOR). Furthermore, saccades typically deviate away from the cued location. The present study examined the relationship between these inhibitory effects. IOR and saccade trajectory deviations were found after central (endogenous) and peripheral (exogenous) cuing of attention, and both effects were larger with an onset cue than with a color singleton cue. However, a dissociation in time course was found between IOR and saccade trajectory deviations. Saccade trajectory deviations occurred at short delays between the cue and the saccade, but IOR was found at longer delays. A model is proposed in which IOR is caused by inhibition applied to a preoculomotor attentional map, whereas saccade trajectory deviations are caused by inhibition applied to the saccade map, in which the final stage of oculomotor programming takes place.

Attention↗
PubMed2004

The role of stimulus-driven and goal-driven control in saccadic visual selection.

Four experiments were conducted to investigate the role of stimulus-driven control in saccadic eye movements. Participants were required to make a speeded saccade toward a predefined target presented concurrently with multiple nontargets and possibly 1 distractor. Target and distractor were either equally salient (Experiments 1 and 2) or not (Experiments 3 and 4). The results uniformly demonstrated that fast eye movements were completely stimulus driven, whereas slower eye movements were goal driven. These results are in line with neither a bottom-up account nor a top-down notion of visual selection. Instead, they indicate that visual selection is the outcome of 2 independent processes, one stimulus driven and the other goal driven, operating in different time windows.

Adult↗
PubMed2004

No blindness for things that do not change.

It is well known that under normal circumstances, human observers are able to detect a visual change (a luminance transient) in the outside world very easily. This study demonstrated that observers are also easily able to detect a nonchanging element if it is located in a display containing multiple elements that do change. That is, a nonchanging element popped out from a display containing multiple changing elements (luminance transients). The efficient detection of the nonchanging element may be due to temporal grouping created by the dynamic character of the stimulus display.

Humans↗
PubMed2004

Attentional capture modulates perceptual sensitivity.

The present study was designed to determine the spatial distribution of attention in displays in which an irrelevant color singleton was present. The results show that the presence of an irrelevant color singleton modulates target detectability (d'). The presence of an irrelevant singleton reduces the gain for input at the target location, particularly when the irrelevant color singleton was close to the target singleton. In line with earlier claims, it is argued that the capture of attention by the irrelevant singleton causes a reduced sensory input at the target location.

Attention↗
PubMed2004

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.

Attention↗
PubMed2004

Top-down search strategies cannot override attentional capture.

Bacon and Egeth (1994) have claimed that color singletons do not interfere with search for a shape singleton when, instead of using a singleton detection mode, participants are forced to use a feature search mode. Bacon and Egeth induced a feature search mode by adding different shape singletons to the display so that observers could not simply respond to uniqueness to find the target. We did exactly the same but used larger display sizes to ensure that the target and distractor singletons remained salient. The results show that under these conditions, an irrelevant color singleton interferes with search for a shape singleton. It is argued that the notion of differential search modes may be incorrect and that the results can be explained in terms of bottom-up salience signals.

Adolescent↗
PubMed2003

Attentional capture within and between objects.

The present study addressed the question whether attentional capture by abrupt onsets is affected by object-like properties of the stimulus field. Observers searched for a target circle at one of four ends of two solid rectangles. In the focused attention condition the location of the upcoming target was cued by means of a central arrowhead, whereas in the divided attention condition, the target location was not cued. Irrelevant abrupt onsets could appear either within the attended or within the non-attended object. The results showed that in the focused attention condition, onsets ceased to capture attention irrespective of whether the onset appeared within an attended object or within a non-attended object.

Adolescent↗
PubMed2003

Parallel allocation of attention prior to the execution of saccade sequences.

In a series of 5 experiments, the allocation of attention prior to the execution of saccade sequences was examined by using a dual-task paradigm. In the primary task, participants were required to execute a sequence of 2 endogenous saccades. The secondary task was a forced-choice letter identification task. During the programming of the saccade sequences, letters were briefly presented at the saccade goals and at no-saccade locations. The results showed that performance was better for letters presented at any of the saccade goals than for letters presented at any of the no-saccade locations. The results support a spatial model that assumes that prior to the execution of a saccade sequence, attention is allocated in parallel to all saccade goals. ((c) 2003 APA, all rights reserved)

Adult↗
PubMed2003

Attentional and oculomotor capture with static singletons.

Previous research has shown that in visual search static singletons have the ability to capture attention (Theeuwes, 1991a, 1992). The present study investigated whether these singletons also have the ability to capture the eyes. Participants had to make an eye movement and respond manually to a shape singleton while a color singleton was present. When participants searched for a unique shape while a unique color singleton was present there was strong attentional and oculomotor capture (Experiment 1). However, when participants searched for a specific-shape singleton (a green circle) when a specific-color singleton (a red element) had to be ignored, there was attentional capture but no oculomotor capture (Experiment 2). The results suggest that an attentional set for a specific feature value defining both the target and the distractor (as in Experiment 2) allows such a fast disengagement of attention from the location of the distractor that a saccade execution to that location is prevented.

Attention↗
PubMed2003

Prioritizing selection of new elements: bottom-up versus top-down control.

Watson and Humphreys (1997) have proposed that prioritized selection of new over old elements occurs because observers can apply top-down inhibition to the locations of the old elements by a mechanism they refer to as visual marking. However, recent evidence has suggested that the top-down mechanism is questionable (Donk & Theeuwes, 2001). In the present study, we investigated whether prioritized selection of new over old elements occurs in a bottom-up or a top-down fashion. Observers were presented with displays containing one set of elements (old elements) followed, after a certain time interval, by a second set of elements (new elements). The observers were instructed to search for the presence of a target that was presented with equal probability among the old and the new elements (Experiments 1 and 2) or twice as often among the old elements than among the new elements (Experiment 3). The results show that new elements were prioritized for selection over old ones even though the observers had no incentive to do so. The results suggest that prioritized selection of new over old elements is not mediated by a top-down inhibition process, as was proposed by Watson and Humphreys (1997). Instead, prioritization of new elements appears to be a bottom-up process. The implications of these results are discussed in terms of models of attentional control.

Adolescent↗
PubMed2003

Inhibition of return spreads across 3-D space.

Focusing attention to a location in 3-D space operates much the same as in 2-D space. Attending a location in 2-D space is followed by a selective inhibitory aftereffect known as inhibition of return (IOR). Here, we report the results of two 3-D reflexive cuing studies in which depth was defined by binocular disparity. As has been shown before, attentional cuing was specific for x-y-z locations. However, the present results show that IOR is not depth specific. After a specific location in x-y-z is cued, IOR occurs for the depth plane in front of and behind the cued location. The finding that IOR spreads across depth planes may be related to how inhibited locations are encoded in the superior colliculus. We argue that the functional role of a depth-blind IOR is to bias attention against going back to any part of a previously attended object.

Attention↗
PubMed2002

Oculomotor capture and Inhibition of Return: evidence for an oculomotor suppression account of IOR.

Previous research has shown that when subjects search for a particular target object the sudden appearance of a new object captures the eyes on a large proportion of trials. The present study examined whether the onset affects the oculomotor system even when the eyes move directly towards the target. Using a modified version of the oculomotor paradigm (see Theeuwes, Kramer, Hahn, & Irwin, 1998) we show that when the eyes moved to the target object, subsequent saccades were inhibited from moving to a location at which a new object had previously appeared (inhibition-of-return; IOR). Whether or not a saccade to the onset was executed had no effect on the size of the inhibition. In particular conditions, the trajectories of saccades to the target objects were slightly curved in the opposite direction of the onset. The data are interpreted in the context of a novel hypothesis regarding oculomotor IOR.

Adult↗
PubMed2002

Programming of endogenous and exogenous saccades: evidence for a competitive integration model.

Participants were required to make a saccade to a uniquely colored target while ignoring the presentation of an onset distractor. The results provide evidence for a competitive integration model of saccade programming that assumes endogenous and exogenous saccades are programmed in a common saccade map. The model incorporates a lateral interaction structure in which saccade-related activation at a specific location spreads to neighboring locations but inhibits distant locations. In addition, there is top-down, location-specific inhibition of locations to which the saccade should not go. The time course of exogenous and endogenous activation in the saccade map can explain a variety of eye movement data, including endpoints, latencies, and trajectories of saccades and the well-known global effect.

Analysis of Variance↗
PubMed2002

Relation between glare and driving performance.

The present study investigated the effects of discomfort glare on driving behavior. Participants (old and young; U. S. and Europeans) were exposed to a simulated low-beam light source mounted on the hood of an instrumented vehicle. Participants drove at night in actual traffic along a track consisting of urban, rural, and highway stretches. The results show that the relatively low glare source caused a significant drop in detecting simulated pedestrians along the roadside and made participants drive significantly slower on dark and winding roads. Older participants showed the largest drop in pedestrian detection performance and reduced their driving speed the most. The results indicate that the deBoer rating scale, the most commonly used rating scale for discomfort glare, is practically useless as a predictor of driving performance. Furthermore, the maximum U. S. headlamp intensity (1,380 cd per headlamp) appears to be an acceptable upper limit.

Adolescent↗