Biomedical subjects

N Lavie

Publications and source records attributed to N Lavie.

At least 19 recordsLinked to original sources

PubMed2001

The role of perceptual load in neglect: rejection of ipsilesional distractors is facilitated with higher central load.

Neglect is known to produce a bias towards the ipsilesional side. Here we examined whether this bias is automatic or can be modulated by manipulating perceptual load in a relevant task [e.g., Lavie, N. (1995). Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Performance, 21, 451-468]. Three patients with left neglect and three healthy controls made speeded choice responses to a target letter in the center of the display while attempting to ignore an irrelevant distractor presented on left or right. Perceptual load was manipulated by inducing a search for the target that appeared with another central stimulus, which was either a blob (low load) or a nontarget letter (higher load). Response competition effects from ipsilesional distractors were significantly reduced by higher load. The same increase of load, however, did not decrease distractor effects in the control group, as expected [e.g., Lavie, N., & Cox, S. (1997). On the efficiency of attentional selection: Efficient visual search results in inefficient rejection of distraction. Psychological Science, 8, 395-398]. These results demonstrate that ipsilesional bias in neglect is not fully automated and emphasize an additional restriction of perceptual capacity. Moreover, they supported our prediction that reduced perceptual capacity in neglect can lead to improved distractor rejection with just small increases in perceptual load.

Aged↗

PubMed2001

The role of working memory in visual selective attention.

The hypothesis that working memory is crucial for reducing distraction by maintaining the prioritization of relevant information was tested in neuroimaging and psychological experiments with humans. Participants performed a selective attention task that required them to ignore distractor faces while holding in working memory a sequence of digits that were in the same order (low memory load) or a different order (high memory load) on every trial. Higher memory load, associated with increased prefrontal activity, resulted in greater interference effects on behavioral performance from the distractor faces, plus increased face-related activity in the visual cortex. These findings confirm a major role for working memory in the control of visual selective attention.

Adult↗

PubMed2001

Processing of irrelevant visual motion during performance of an auditory attention task.

The extent to which irrelevant perception of visual motion distractors can be modulated by manipulating auditory load in a relevant task was assessed with Positron Emission Tomography (PET) and behavioural experiments. Subjects performed an auditory task and ignored an irrelevant visual motion stimulus, under two conditions. In a low load condition, subjects were asked to detect words spoken in a loud voice among words spoken in a quiet voice, while in a high load condition they attempted to detect bisyllabic words among monosyllabic and trisyllabic words. We found that motion-related visual areas were strongly activated by the irrelevant motion stimulus, compared to a static stimulus, under both conditions of load in the auditory task. In a second behavioural experiment, the duration of the motion after-effect was similarly unaffected by adaptation under low or high auditory load. These results are in clear contrast with the strong modulation of irrelevant motion processing by visual load, as reflected in the duration of the motion after effect (Section 6) and neural responses in motion-related visual areas (Rees et al., Science, (1997) 278, 338). These findings support the claim that attentional capacity is restricted within but not between sensory modalities, and indicate that processing of visual distractors may occur whenever there is sufficient visual capacity to process them, despite being task- and modality-irrelevant.

Adult↗

PubMed2001

What can functional imaging reveal about the role of attention in visual awareness?

This review focuses on neuroimaging studies that address the relationship between selective attention, neural activity and visual awareness. Withdrawing attention from particular visual stimuli reduces modality-specific processing in posterior visual cortex, and when attention is fully engaged elsewhere, even highly salient but task-irrelevant stimuli can fail to evoke activity and reach awareness. However, the link between visual attention and awareness extends beyond posterior visual cortex to also encompass regions of parietal and prefrontal cortex. Activity in the posterior visual cortex may be necessary but not sufficient for awareness, without a contribution from frontal and parietal cortex. Consistent with this, enhanced interactions between parietal, frontal and posterior visual cortex are observed as a function of both visual attention and visual awareness; and lesions of parietal cortex disrupt both visual attention and awareness. Taken together, these data suggest that distributed interactions between modality-specific posterior visual cortex and frontoparietal areas subserve both visual attention and visual awareness.

Attention↗

PubMed2001

Neural correlates of change detection and change blindness.

Functional magnetic resonance imaging (fMRI) of subjects attempting to detect a visual change occurring during a screen flicker was used to distinguish the neural correlates of change detection from those of change blindness. Change detection resulted in enhanced activity in the parietal and right dorsolateral prefrontal cortex as well as category-selective regions of the extrastriate visual cortex (for example, fusiform gyrus for changing faces). Although change blindness resulted in some extrastriate activity, the dorsal activations were clearly absent. These results demonstrate the importance of parietal and dorsolateral frontal activations for conscious detection of changes in properties coded in the ventral visual pathway, and thus suggest a key involvement of dorsal-ventral interactions in visual awareness.

Adult↗

PubMed2001

Changing faces: a detection advantage in the flicker paradigm.

Observers seem surprisingly poor at detecting changes in images following a large transient or flicker. In this study, we compared this change blindness phenomenon between human faces and other common objects (e.g., clothes). We found that changes were detected far more rapidly and accurately in faces than in other objects. This advantage for faces, however, was found only for upright faces in multiple-object arrays, and was completely eliminated when displays showed one photograph only or when the pictures were inverted. These results suggest a special role for faces in competition for visual attention, and provide support for previous claims that human faces are processed differently than stimuli that may be of less biological significance.

Awareness↗

PubMed2000

The role of perceptual load in negative priming.

Negative priming (NP) effects from irrelevant distractors were assessed as a function of perceptual load in the processing of prime targets. Participants searched for a target letter among a varying number of nontarget letters in the center of the display and ignored an irrelevant peripheral distractor. NP from this distractor was found to depend on the relevant search set size, decreasing as this set size was increased. The authors conclude that exhausting attention in relevant processing reduces irrelevant processing (e.g., N. Lavie, 1995), leaving less distractor processing to produce NP. This conclusion is consistent with recent reactive inhibition views for NP (e.g., G. Houghton, S. P. Tipper, B. Weaver, & D. I. Shore, 1996).

Attention↗

PubMed1999

Effect of articulatory and mental tasks on postural control.

The present study sought to determine whether the increased postural instability produced by a spoken mental task was due to competing demands for attentional resources or perturbation of posture by articulation. Postural sway was measured in 36 normal subjects under the following conditions: repeating a number aloud (articulation), counting backwards aloud in multiples of seven (articulation and attention), counting backwards silently (attention), and no mental task (neither articulation nor attention). Articulation resulted in a significant increase in sway, whereas no effect of attention was observed. We conclude that in order to accurately assess the effect of attentional demands on postural control, it is important to eliminate or control the effects of articulation.

Adolescent↗

PubMed1999

Attentional demands of perception of passive self-motion in darkness.

The purpose of this study was to determine whether significant attentional resources are required to accurately monitor changes in bodily orientation, using vestibular information. This question was addressed firstly using a dual-task paradigm in which orientation perception tasks and a speeded auditory tone discrimination task were carried out either singly or in combination. For the active orientation perception task, subjects were seated in darkness on a motorised chair which could be rotated about an earth-vertical axis. Following passive angular displacements, subjects were required to return the chair to their perceived starting position, using a joy-stick which controlled chair motion. For the speeded auditory task, subjects pushed a hand-held button as fast as possible when a tone was presented over headphones. When the two tasks were combined, reaction times on the auditory task increased. Reaction time also increased when subjects were simply asked to fixate during rotation. A second experiment demonstrated that if attention was occupied by performance of a demanding mental arithmetic task during the passive rotation, accuracy of subsequently repositioning the chair to the origin declined, implying that change in orientation had been less accurately registered when performing the concurrent mental task. In combination, these findings indicate that a small but significant degree of attention or cognitive effort is necessary to monitor accurately the direction and amplitude of a brief angular rotation, and to suppress vestibulo-ocular reflex eye movement.

Adult↗

PubMed1998

The influence of perceptual load on age differences in selective attention.

The effect of perceptual load on age differences in visual selective attention was examined in 2 studies. In Experiment 1, younger and older adults made speeded choice responses indicating which of 2 target letters was present in a relevant set of letters in the center of the display while they attempted to ignore an irrelevant distractor in the periphery. The perceptual load of relevant processing was manipulated by varying the central set size. When the relevant set size was small, the adverse effect of an incompatible distractor was much greater for the older participants than for the younger ones. However, with larger relevant set sizes, this was no longer the case, with the distractor effect decreasing for older participants at lower levels of perceptual load than for younger ones. In Experiment 2, older adults were tested with the empty locations in the central set either unmarked (as in Experiment 1) or marked by small circles to form a group of 6 items irrespective of set size; the 2 conditions did not differ markedly, ruling out an explanation based entirely on perceptual grouping.

Adult↗

PubMed1997

Modulating irrelevant motion perception by varying attentional load in an unrelated task.

Lavie's theory of attention proposes that the processing load in a relevant task determines the extent to which irrelevant distractors are processed. This theory was tested by asking participants in a study to perform linguistic tasks of low or high load while ignoring irrelevant visual motion in the periphery of the display. Although task and distractor were unrelated, both functional imaging of motion-related activity in cortical area V5 and psychophysical measures of the motion aftereffect showed reduced motion processing during high load in the linguistic task. These findings fulfill the prediction that perception of irrelevant distractors depends on the relevant processing load.

Adult↗

PubMed1997

Contrast discrimination function: spatial cuing effects.

The effects of spatial cuing were measured for discrimination between an increment and a decrement on a target's pedestal contrast. Discrimination thresholds measured in the absence of a spatial cue were always higher than corresponding thresholds measured in the presence of a spatial cue, except when pedestal contrast was near zero. Uncued discrimination thresholds rose monotonically with pedestal contrast; cued discrimination thresholds formed a dipper function of pedestal contrast. A spatial-uncertainty model incorporating a nonlinear transducer produced similar results.

Contrast Sensitivity↗

PubMed1997

Visual feature integration and focused attention: response competition from multiple distractor features.

Predictions from Treisman's feature integration theory of attention were tested in a variant of the response-competition paradigm. Subjects made choice responses to particular color-shape conjunctions (e.g., a purple cross vs. a green circle) while withholding their responses to the opposite conjunctions (i.e., a purple circle vs. a green cross). The results showed that compatibility effects were based on both distractor color and shape. For unattended distractors in preknown irrelevant positions, compatibility effects were equivalent for conjunctive distractors (e.g., a purple cross and a blue triangle) and for disjunctive distractors (e.g., a purple triangle and a blue cross). Manipulation of attention to the distractors positions resulted in larger compatibility effects from conjoined features. These results accord with Treisman's claim that correct conjunction information is unavailable under conditions of inattention, and they provide new information on response-competition effects from multiple features.

Adult↗

PubMed1996

On the spatial extent of attention in object-based visual selection.

A new test was devised to avoid previous confounds in measures of object-based limits on divided visual attention. The distinction between objects was manipulated across a wide spatial extent. Target elements appeared on the same object only when far apart, and appeared close only when on different objects, so that object effects could not be reduced to spatial effects, nor vice versa. Subjects judged whether two odd elements within a display of two dashed lines were the same or different. They performed better when the target elements were far apart on a common line rather than on two distinct lines even though the latter arrangement was more likely. Thus, nonstrategic object-based limits on divided attention can arise even across large distances. However, when subjects were precued to expect targets in a narrow region of the display, the object effect was eliminated, implying that object-based selection may only operate within spatially attended regions.

Adolescent↗

PubMed1995

Perceptual load as a necessary condition for selective attention.

The early and late selection debate may be resolved if perceptual load of relevant information determines the selective processing of irrelevant information. This hypothesis was tested in 3 studies; all used a variation of the response competition paradigm to measure irrelevant processing when load in the relevant processing was varied. Perceptual load was manipulated by relevant display set size or by different processing requirements for identical displays. These included the requirement to process conjunctions versus isolated features and the requirement to perform simple detection of a character's presence versus difficult identification of its size and position. Distractors' interference was found only under low-load conditions. Because the distractor was usually clearly distinct from the target, it is concluded that physical separation is not a sufficient condition for selective perception; overloading perception is also required. This allows a compromise between early and late selection views and resolves apparent discrepancies in previous work.

Adult↗

PubMed1994

The role of attention in illusory conjunctions.

In five experiments, we investigated the effects of attention on illusory conjunctions formed between features of unrelated objects. The first three experiments used a weak manipulation of attention and found that illusory conjunctions formed either among features receiving high attentional priority or among features receiving low attentional priority were not more frequent than were conjunctions formed between mixed features of different attentional priority. The last two experiments used a strong manipulation of attention and failed to reveal any evidence of true illusory conjunctions. The results are inconsistent with the feature-integration theory, which predicts that when attention is focused on a subset of items, illusory conjunctions ought to occur within and outside of the attended subset, but not between the attended and unattended items.

Attention↗

PubMed1994

Perceptual load as a major determinant of the locus of selection in visual attention.

In this paper, we propose that the debate concerning the locus of attentional selection can be resolved by specifying the conditions under which early selection is possible. In the first part, we present a theoretical discussion that integrates aspects from structural and capacity approaches to attention and suggest that perceptual load is a major factor in determining the locus of selection. In the second part, we present a literature review that examines the conditions influencing the processing of irrelevant information. This review supports the conclusion that a clear physical distinction between relevant and irrelevant information is not sufficient to prevent irrelevant processing; early selection also requires that the perceptual load of the task be sufficiently high to exceed the upper limit of available attentional resources.

Attention↗

PubMed1993

Location dominance in attending to color and shape.

Four experiments investigated whether Ss direct attention to stimulus location when attempting to attend to its color or shape. In the first 2 experiments a given property (location, color, or shape) of a letter cue instructed Ss whether to report any letters from a subsequent display. Regardless of which property was relevant, Ss reported letters adjacent to the cue and not those similar to its color or shape. In the last 2 experiments, the varied location of a cue was irrelevant to the task, whereas its varied color instructed Ss to report a letter in a given location or of a given shape. Targets adjacent to the cue were reported faster than those remote from the cue. The results suggest that attempting to attend to any aspect of a stimulus entails directing attention to its location.

Adult↗