Attentional distribution in visual space

Summary The horizontal extent of the visual attentive field was measured by the use of a two-choice-RT task and compatible and incompatible distractors. The target was a line that inclined either to the left or to the right. Whether or not the subject performed the choice RT was made contingent upon whether two other stimuli presented in the visual display matched or mismatched. The match-mismatch stimuli varied in locations so as to manipulate the relevant visual area (the attended area). The locations of the distractors were also varied. The increase in RT associated with incompatible distractors was found to vary inversely with their distance from the edge of the area attended to and independently of their distance from the target lines. The results were interpreted in terms of an inhibitory field that surrounds the area attended to.     

Attentional factors in visual field asymmetries.

Over the past 30 years, numerous studies have reported left/right asymmetries in visual field performance, with performance generally superior in the right visual field for verbal tasks and in the left visual field for spatial tasks. These asymmetries parallel those found in neurological studies of hemispheric specialization. Consequently, many investigators have concluded that visual hemifield differences are primarily a reflection of the functional differences between the two cerebral hemispheres. However, alternative explanations proposing that visual field effects are dependent on other factors such as inadequate fixation, eye movements during presentation, postexposural scanning, and attentional biases have been offered. The potential impact of each of these factors on visual field differences are reviewed and discussed. Evidence is provided suggesting that attention and hemispheric functional differences interact to produce the magnitude and direction of visual field differences.     

Upper and lower visual field differences in categorical and coordinate judgments

Kosslyn (1987) theorized that the left and right hemispheres differ in processing categorical and coordinate spatial relationships, respectively. Previc (1990) hypothesized that the upper and lower visual fields are functionally specialized for visual search and visuomotor manipulations, respectively. Conceptual similarities between these two theories suggested possible upper visual field advantages for categorical judgments and lower visual field advantages for coordinate judgments. In the present two experiments, subjects made either categorical or coordinate judgments to stimuli in the upper left, upper right, lower left, or lower right visual fields. The first experiment manipulated categorical/coordinate judgments as a between-subjects variable. The second experiment manipulated categorical/coordinate judgments as a within-subjects variable. In the first experiment, reaction times (RTs) for categorical judgments were equal in all visual fields except the lower left, in which RTs were slower. For coordinate judgments, RTs were equal in all visual fields except the lower left, in which RTs were faster. In general, these effects were replicated in the second experiment. However, there appeared to be consequences associated with manipulating the categorical/coordinate variable in a within-subjects fashion. The requirements of visual search versus visuomotor processes appear to map onto the nature of categorical versus coordinate processing, respectively, suggesting possible upper-lower visual field differences in categorical versus coordinate processing.     

Attentional episodes in visual perception

Is one's temporal perception of the world truly as seamless as it appears? This article presents a computationally motivated theory suggesting that visual attention samples information from temporal episodes (episodic simultaneous type/serial token model; Wyble, Bowman, & Nieuwenstein, 2009). Breaks between these episodes are punctuated by periods of suppressed attention, better known as the attentional blink (Raymond, Shapiro, & Arnell, 1992). We test predictions from this model and demonstrate that participants were able to report more letters from a sequence of 4 targets presented in a dense temporal cluster than from a sequence of 4 targets interleaved with nontargets. However, this superior report accuracy comes at a cost in impaired temporal order perception. Further experiments explore the dynamics of multiple episodes and the boundary conditions that trigger episodic breaks. Finally, we contrast the importance of attentional control, limited resources, and memory capacity constructs in the model.     

Attentional misguidance in visual search

Previous research has shown that a task-irrelevant sudden onset of an object will capture an observer’s visual attention or draw it to that object (e.g., Yantis & Jonides, 1984). However, further research has demonstrated the apparent inability of an object with a task-irrelevant but unique color or luminance to capture attention (Jonides & Yantis, 1988). In the experiments reported here, we reexplore the question of whether task-irrelevant properties other than sudden onset may capture attention. Our results suggest that uniquely colored or luminous objects, as well as salient though irrelevant boundaries, do not appear to capture attention. However, these irrelevant features do appear to serve as landmarks for a top-down search strategy which becomes increasingly likely with larger display set sizes. These findings are described in terms of stimulus-driven and goal-directed aspects of attentional control.     

Attentional holism in visual word processing

Summary Decisions about the identity of an entire word are made more quickly than decisions about the identity of a letter within a word. Explanations of this whole-word advantage based on the time-course of the activation of different levels of unit detectors have given way to explanations based on how attention is allocated to the output of the detectors. Three studies were carried out to examine the role of attention in the whole-word advantage. In Experiment 1, cues as to the level of decision (whole-word vs. first-letter) facilitated component processing, a finding that suggests word level information is normally the focus of attention. In Experiment 2, identification of a probe item to the right of a display was longer when subjects prepared for a first-letter rather than a whole-word decision. That is, the spatial extent of attention is wider for whole-word decisions. In Experiment 3, probe latencies were longer when subjects prepared for a whole-word decision than when they prepared for a signalled probe trial. Preparation for a whole-word decision is not automatic in the sense of being free of capacity demands. The overall pattern of results leads to the conclusion that the whole-word advantage is an instance of attentional holism.     

Attentional priming and visual search in pigeons

Advance information about a target's identity improved visual search efficiency in pigeons. Experiments 1 and 2 compared information supplied by visual cues with information supplied by trial sequences. Reaction times (RTs) were lower when visual cues signaled a single target rather than two. RTs were (Experiment 1) or accuracy improved (Experiment 2) when a sequence of trials presented a single target rather than a mixture of 2. Experiments 3, 4, and 5 considered the selectivity of visual priming by introducing probe trials that reversed the usual cue-target relationship. RT was higher following such miscues than following the usual 1- or 2- target cuing relationships (Experiment 3); the miscuing effect persisted over variations in the target's concealment (Experiments 4 and 5), but did not occur when the target was presented alone (Experiment 4). The findings indicate that priming modifies an attentional mechanism and suggest that this effect accounts for search images.     

Attentional interference in judgments of musical timbre: individual differences in working memory

Researchers have shown that working memory is related to a variety of high-level cognitive processes. However, the results of recent research have suggested that may be because of its role in attentional control. In the present experiment, the authors investigated that hypothesis by using an attentional interference task with musical stimuli. Listeners were asked to monitor one ear for either a clarinet or violin tone and to ignore any information in the other ear. On some of the trials, they heard only one tone and on other trials, either the same instrument in both ears or different instruments. Individual differences were measured in working memory and musical experience. The results showed more attentional interference in the different-instrument condition for participants with lower working memory scores, which suggested that working memory involves the ability to control attention to inhibit irrelevant information.     

Attentional strategies and the visual control of discrete movements

The relationship between the availability of visual information and attention demands during the production of a discrete motor act was examined. Subjects were required to move a linear slide a distance of 15 cm in both 150 and 600 msec conditions under three light manipulations, viz., light always on; light always terminated as movement began; or, subject was unsure as to whether light would stay on or terminate. A simple key press by the index finger of the opposite hand to a tone was used as a secondary task and a measure of attention demands. The light manipulation influenced attention demands on the rapid 150 msec movement such that more attention was demanded when the subject knew the light would terminate. No such attentional strategy differences were found with the slow 600 msec movement. These findings suggest that task constraints in the form of kinematic criteria, together with the perceived availability of visual information, contribute to determining attentional strategy in movement production.     

Attentional modulation in perception of visual motion events.

Identical visual targets moving across each other with equal and constant speed can be perceived either to bounce off or to stream through each other. This bistable motion perception has been studied mostly in the context of motion integration. Since the perception of most ambiguous motion is affected by attention, there is the possibility of attentional modulation occurring in this case as well. We investigated whether distraction of attention from the moving targets would alter the relative frequency of each percept. During the observation of the streaming/bouncing motion event in the peripheral visual field, visual attention was disrupted by an abrupt presentation of a visual distractor at various timings and locations (experiment 1; exogenous distraction of attention) or by the demand of an additional discrimination task (experiments 2 and 3; endogenous distraction of attention). Both types of distractions of attention increased the frequency of the bouncing percept and decreased that of the streaming percept. These results suggest that attention may facilitate the perception of object motion as continuing in the same direction as in the past.     

Attentional set interacts with perceptual load in visual search

In the present study, we examined the hypothesis that perceptual load is the primary factor that determines the efficiency of attentional selection. Participants performed a visual search task under conditions of high- and low-load. In line with the perceptual load hypothesis, presenting conditions of highand low-load in separate blocks of trials resulted in processing of to-be-ignored stimuli only in the lowload condition (Experiment 1). However when high- and low-load conditions were randomly mixed in blocks of trials, the participants showed processing of to-be-ignored stimuli in both conditions, suggesting that high perceptual load is not necessarily sufficient to obtain perceptual selectivity (Experiment 2). An analysis of intertrial transition effects showed that on high-load trials, processing of to-be-ignored stimuli occurred only when the previous trial was a low-load trial. The results suggest that low perceptual load can engender broad attentional processing. On the other hand, when a high-load trial was preceded by another high-load trial, little processing of task-irrelevant stimuli was observed. The present results are discussed in terms of the interaction between expectancies and bottom-up factors in the efficiency of attentional selection.     

Attentional resources in visual tracking through occlusion: the high-beams effect

A considerable amount of research has uncovered heuristics that the visual system employs to keep track of objects through periods of occlusion. Relatively little work, by comparison, has investigated the online resources that support this processing. We explored how attention is distributed when featurally identical objects become occluded during multiple object tracking. During tracking, observers had to detect small probes that appeared sporadically on targets, distracters, occluders, or empty space. Probe detection rates for these categories were taken as indexes of the distribution of attention throughout the display and revealed two novel effects. First, probe detection on an occluder’s surface was better when either a target or distractor was currently occluded in that location, compared to when no object was behind that occluder. Thus even occluded (and therefore invisible) objects recruit object-based attention. Second, and more surprising, probe detection for both targets and distractors was always better when they were occluded, compared to when they were visible. This new attentional high-beams effect indicates that the ability to track through occlusion, though seemingly effortless, in fact requires the active allocation of special attentional resources.     

Attentional processes in young children with congenital visual impairment

The study investigated attentional processes of 32 preschool children with congenital visual impairment (VI). Children with profound visual impairment (PVI) and severe visual impairment (SVI) were compared to a group of typically developing sighted children in their ability to respond to adult directed attention in terms of establishing, maintaining, and shifting attention on toys. The measures of children's sensory‐motor understanding (SMU) and language ability were obtained using the Reynell‐Zinkin scales of mental development. The video‐recordings of these play‐based assessments were coded for three categories of behavioural responses (Establish, Maintain, and Shift). The three groups were matched on verbal comprehension (VC), but differed significantly in their SMU and their chronological age. The groups of children with PVI and SVI were found to be comparable in their ability to establish and maintain attention on objects. Despite a relatively good performance overall both groups scored significantly lower on those skills than children who were sighted. However, with regards to attention shifting, children with PVI showed significantly lower performance than both the children with SVI and the sighted children who were similar on this component. Ability to maintain and shift attention was significantly related to the cognitive ability of children with PVI; however the poorer attentional responses were not confined only to the children with low IQ. The results are discussed in relation to the role of vision, cognitive ability and executive function in attentional processes in children with congenital VI.     

Duration judgments of naturalistic events in the auditory and visual modalities

Two experiments were performed to examine whether the same underlying mechanisms apply to the duration estimates of both auditory and visual events. In Experiment 1, it was found that the durations of visual scenes are reproduced with the same level of accuracy in prospective and retrospective situations when these display a predictable array of information, a result consistent with past research on auditory durations. Experiment 2 further revealed that when participants are asked to prospectively or retrospectively judge the durations of various naturalistic events in their auditory, visual, or audiovisual modality, no differences in either accuracy or bias are observed. These findings diverge from previous research and are argued to stem from different processing mechanisms that arise from naturalistic events.