Global precedence in attended and nonattended objects

In four experiments we evaluated whether there is a priority in early perceptual analysis for the global aspect of a nonattended, visual, compound stimulus. In all experiments, two objects were distinguished by being enclosed in either a square or a circle, and each object consisted of a larger letter constructed from smaller letters. Attention was directed to one of the two objects on the basis of either the square/circle distinction (Experiments 1, 2, and 3) or a visual precue (Experiment 4). In agreement with previous findings, for attended objects, the global aspect was identified faster and was more difficult to ignore than the local aspect. However, for nonattended objects, no evidence was found for an overall priority in perceptual processing leading to identification of the global aspect. Rather, the results indicate that there is a priority in perceptual processing for the general category of the global information contained within nonattended objects. Although the results provide some support for the view that global information receives priority during early perceptual analysis, aspects of the results are more consistent with postidentification accounts of global precedence.     

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.     

Attentional prioritization to contextually new objects

Using a hybrid paradigm of a contextual cuing task and a probe detection task, we tested whether or not contextually new objects can be prioritized in visual search. After several hundred visual search practice trials with repeated and nonrepeated layouts, an additional distractor that was contextually new was presented in the repeated layouts. The results showed that detection of probe dots appearing at the location of a search target was faster in the repeated than in the nonrepeated layouts. More importantly, detection of probe dots at the new object locations was as fast as that of probe dots at the target locations in repeated layouts, suggesting that the attentional system implicitly prioritizes the processing of a location where a change in contextual information has occurred.     

Attentional capture by globally defined objects

The abrupt appearance of a new perceptual object in the visual field typically captures visual attention. However, if attention is focused in advance on a different location, onsets can fail to capture attention (Yantis & Jonides, 1990). In the present experiments, we investigated the extent to which the deployment of attention to the local level of a hierarchical scene may be affected by the abrupt appearance of a new object at the global level. Participants searched for a semi-disk target in an array of randomly oriented segmented disks (“pacmen”). On half the trials, a subset of the segmented disks induced a subjective square. On these critical trials, participants were significantly slower to respond to the presence of a local target even though the local features of the display were qualitatively identical across all conditions. This slowing was absent when outline pacmen were used (which do not induce subjective figures) and when the subjective square was perceptually old. When the participants’ task was defined at the global level of the display, a new local element failed to capture attention, suggesting an asymmetry in the ability of objects at different levels of a hierarchical scene to capture attention. In a control experiment, a new local element captured attention, however, when the participants’ task was defined at the local level, indicating that the local item was in principle capable of capturing attention. It is argued that global objects capture attention because they convey important information about the environment that is not available at the local level.     

Attentional capture by globally defined objects.

The abrupt appearance of a new perceptual object in the visual field typically captures visual attention. However, if attention is focused in advance on a different location, onsets can fail to capture attention (Yantis & Jonides, 1990). In the present experiments, we investigated the extent to which the deployment of attention to the local level of a hierarchical scene may be affected by the abrupt appearance of a new object at the global level. Participants searched for a semi-disk target in an array of randomly oriented segmented disks ("pacmen"). On half the trials, a subset of the segmented disks induced a subjective square. On these critical trials, participants were significantly slower to respond to the presence of a local target even though the local features of the display were qualitatively identical across all conditions. This slowing was absent when outline pacmen were used (which do not induce subjective figures) and when the subjective square was perceptually old. When the participants' task was defined at the global level of the display, a new local element failed to capture attention, suggesting an asymmetry in the ability of objects at different levels of a hierarchical scene to capture attention. In a control experiment, a new local element captured attention, however, when the participants' task was defined at the local level, indicating that the local item was in principle capable of capturing attention. It is argued that global objects capture attention because they convey important information about the environment that is not available at the local level.     

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 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.     

Memory for attended and unattended visual stimuli

Subjects were presented with lists of 'compound letters,' letters whose overall shapes were described by repeated use of replicates of other, smaller letters. In Experiment 1 subjects were asked to attend to either the overall letter or the smaller, constituent letter. At the end of list presentation, recall of all letters was required, but a postlist cue determined whether the attended or unattended letters were to be reported first. The results for four-item lists accorded with those of Martin (1978, 1980): order of report had a larger effect upon retention of attended letters than upon retention of unattended letters. The findings for three-item lists did not agree with Martin, however: first, the interaction of attention and order was weak; second, sharp recency for unattended letters was not found.

Experiment 2 required that subjects recall either in temporal pairs or by letter size. The results strongly suggest that the present paradigm does not constitute an analogue to dichotic listening. In particular, there is little evidence for a role for sensory retention of compound letters at time of recall.     

Attentional set protects visual marking from visual transients

When some distractors (old items) appear before others (new items) in an inefficient visual search task, the old items are excluded from the search (visual marking). Previous studies have shown that changing the shape of old items eliminates this effect, suggesting that shape identity must be maintained for successful visual marking. However, the contribution of top-down target knowledge to the maintenance of visual marking under shape change conditions has not been systematically examined. The present study tested whether the vulnerability of visual marking to shape change is contingent on observers' attentional set, by manipulating compatibility of the set and the domains in which the change occurs. The results indicated that visual marking survived shape changes when the observer's attentional set was consistent with critical features between the old and new items. This protection was observed when the set was based on explicit instructions at the beginning of the experiment, and when the task set was implicitly carried over from the previous task. These results suggest that top-down processes play a role in maintaining memory templates by enhancing the grouping and suppression processes during visual search, despite disruptive bottom-up signals.     

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.     

Failure to detect changes to attended objects in motion pictures

Our intuition that we richly represent the visual details of our environment is illusory. When viewing a scene, we seem to use detailed representations of object properties and interobject relations to achieve a sense of continuity across views. Yet, several recent studies show that human observers fail to detect changes to objects and object properties when localized retinal information signaling a change is masked or eliminated (e.g., by eye movements). However, these studies changed arbitrarily chosen objects which may have been outside the focus of attention. We draw on previous research showing the importance of spatiotemporal information for tracking objects by creating short motion pictures in which objects in both arbitrary locations and the very center of attention were changed. Adult observers failed to notice changes in both cases, even when the sole actor in a scene transformed into another person across an instantaneous change in camera angle (or “cut”).     

Attentional demands of visual word recognition

Becker's (1976, 1979, 1980, 1985; Becker & Killion, 1977; Eisenberg & Becker, 1982) verification model was used as a framework to investigate the attentional demands of word recognition. In two experiments, a lexical decision task and an auditory probe task were performed in single- and dual-task conditions. Responses to probes were divided into detection and movement measures that indexed the demands of recognition and response output, respectively. In Experiment 1, single- to dual-task decrements in probe detection performance were larger during low-frequency as compared with high-frequency trials. This finding indicates that the attentional demands of word recognition vary with word frequency. These findings were replicated in Experiment 2, which was designed to separate a response compatibility and a capacity interpretation of the results. The findings are interpreted within Becker's verification model.     

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.     

Auditory and visual objects

Notions of objecthood have traditionally been cast in visuocentric terminology. As a result, theories of auditory and cross-modal perception have focused more on the differences between modalities than on the similarities. In this paper we re-examine the concept of an object in a way that overcomes the limitations of the traditional perspective. We propose a new, cross-modal conception of objecthood which focuses on the similarities between modalities instead of the differences. Further, we propose that the auditory system might consist of two parallel streams of processing (the 'what' and 'where' subsystems) in a manner analogous to current conceptions of the visual system. We suggest that the 'what' subsystems in each modality are concerned with objecthood. Finally, we present evidence for - and elaborate on - the hypothesis that the auditory 'where' subsystem is in the service of the visual-motor 'where' subsystem.     

Attentional capture of objects referred to by spoken language

Participants saw a small number of objects in a visual display and performed a visual detection or visual-discrimination task in the context of task-irrelevant spoken distractors. In each experiment, a visual cue was presented 400 ms after the onset of a spoken word. In experiments 1 and 2, the cue was an isoluminant color change and participants generated an eye movement to the target object. In experiment 1, responses were slower when the spoken word referred to the distractor object than when it referred to the target object. In experiment 2, responses were slower when the spoken word referred to a distractor object than when it referred to an object not in the display. In experiment 3, the cue was a small shift in location of the target object and participants indicated the direction of the shift. Responses were slowest when the word referred to the distractor object, faster when the word did not have a referent, and fastest when the word referred to the target object. Taken together, the results demonstrate that referents of spoken words capture attention.     

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.     

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.     

Spatial interference between attended items engenders serial visual processing

A pair of experiments investigated the architecture of visual processing, parallel versus serial, across high and low levels of spatial interference in a divided attention task. Subjects made speeded judgments that required them to attend to a pair of color-cued objects among gray filler items, with the spatial proximity between the attended items varied to manipulate the strength of interference between attended items. Systems factorial analysis (Townsend & Nozawa, Journal of Mathematical Psychology 39:321-359, 1995) was used to identify processing architecture. Experiment 1, using moderately dense displays, found evidence of parallel processing whether attended objects were in low or high proximity to one another. Experiment 2, using higher-density displays, found evidence of parallel selection when attended stimuli were widely separated but serial processing when they were in high proximity. Divided visual attention can operate in parallel under conditions of low or moderate spatial interference between selected items, but strong interference engenders serial processing.     

Attentional and structural constraints on visual encoding

We examined the mechanisms that mediate the transfer of information from visual input to storage in memory. Observers performed two concurrent tasks, one of which required input into memory. We discovered that the processes involved in the transfer of information from sensory input into memory cause slowing in concurrent cognitive tasks (dual-task slowing). We used the dual-task slowing effect to demonstrate that memory encoding requires more time when more information is to be encoded and to show that dual-task slowing occurs long after the initial perceptual encoding of visual information (Exp. 1). These results suggest a late and central locus of interaction between the two tasks. Experiment 2 also used two concurrent tasks. However, we reversed the direction of interaction between them and produced a memory deficit from the execution of a concurrent task. Together the results suggest that the mechanisms that encode information into memory belong to a family of mechanisms that are involved in dual-task slowing phenomena and that have been studied under the rubric of the PRP effect (psychological refractory period). We were able to locate the most probable locus of the dual-task interactions to a process that appears necessary for memory encoding. We call this process short-term consolidation. Received: 20 July 1997 / Accepted: 17 March 1998