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Biomedical subjects

A Treisman

Publications and source records attributed to A Treisman.

At least 19 recordsLinked to original sources
PubMed2001

Objects and their locations in exogenous cuing.

Anatomical, physiological, and behavioral studies provide support for separate object- and location-based components of visual attention. Although studies of object-based components have usually involved voluntary attention, more recent evidence has suggested that objects may play an independent role in reflexive exogenous orienting, at least at long stimulus onset asynchronies (SOAs). In the present experiments, the role of objects in reflexive attentional orienting was investigated by developing a task in which location and object cuing could be separately examined for both short and long SOAs. Typical location cuing effects were obtained, indicating facilitation at short cue-target intervals and inhibition of return (IOR) at longer intervals. In contrast, object cuing resulted in facilitation for cued objects at long cue-target intervals and no object-based IOR. Interestingly, object cuing primarily affected targets at cued locations, and not those at uncued locations. Together, the experiments examine the interactive nature of objects and locations in exogenous orienting and seem most consistent with a location-mediated view of object-based orienting.

Adult↗
PubMed2001

The midstream order deficit.

The relative order of an auditory sequence can be more difficult to apprehend when it is presented repeatedly without pause (i.e., cycling) than when it is presented only once (Warren, Obusek, Farmer, & Warren, 1969). We find that this phenomenon, referred to as the midstream order deficit (MOD), can also occur with visual stimuli. The stimuli need not form separate perceptual "streams," and the effect can occur with presentation rates as slow as five items per second, even though the identification of individual letters is very accurate at this rate. However, if the first item of the sequence is visually very distinct from the preceding items, relative order reports can be as accurate in the cycling condition as in the single-presentation condition. Our results suggest that the MOD is not due to masking, attentional blink, repetition blindness, Reeves and Sperling's (1986) order illusion, memory limitations, or decision criteria. The MOD may reflect an attentional cost to the initiation of order encoding, which is distinct from the allocation of attention is required in order to detect and identify individual items. To initiate order encoding successfully, one's attention must be set for, or captured by, an initial salient event.

Adult↗
PubMed1998

Feature binding, attention and object perception.

The seemingly effortless ability to perceive meaningful objects in an integrated scene actually depends on complex visual processes. The 'binding problem' concerns the way in which we select and integrate the separate features of objects in the correct combinations. Experiments suggest that attention plays a central role in solving this problem. Some neurological patients show a dramatic breakdown in the ability to see several objects; their deficits suggest a role for the parietal cortex in the binding process. However, indirect measures of priming and interference suggest that more information may be implicitly available than we can consciously access.

Attention↗
PubMed1997

Voluntary attention modulates fMRI activity in human MT-MST.

How does voluntary attention to one attribute of a visual stimulus affect the neural processing of that stimulus? We used functional magnetic resonance imaging to examine the attentional modulation of neural activity in the human homolog of the MT-MST complex, which is known to be involved in the processing of visual motion. Using a visual stimulus containing both moving and stationary dots, we found significantly more MT-MST activation when subjects attended to the moving dots than when they attended to the stationary dots, even though the visual stimulus was identical during the two conditions.

Adult↗
PubMed1996

The binding problem.

Perceptual representations depend on distributed neural codes for relaying the parts and properties of objects. Some mechanism is needed to 'bind' the information relating to each object and to distinguish it from others. Possible candidates include cells tuned to conjunctions of features, spatial attention, and synchronized firing across separate but interconnected areas of the brain. Deficits in neurological patients suggest a role for the parietal cortex in the binding process. Several current models combine these ideas.

Brain↗
PubMed1996

Visual memory for novel shapes: implicit coding without attention.

Implicit memory for novel shapes was explored with a negative priming paradigm. The results show that representations of shapes, formed in a single trial and without attention, can last without decrement across 200 intervening trials and with temporal delays of up to a month. No explicit memory of the shapes was available, either immediately or after a delay. There were consistent individual differences in the amount of negative priming shown, and some participants showed only facilitation. There was a trend toward increased facilitation across time, as if the memory of the shape survived longer than an "action tag" attached to it, which specified whether it should be attended or ignored. The results demonstrate a surprising combination of plasticity and permanence in the visual system and suggest that the roles of both attention and repetition may be to ensure voluntary retrievability rather than to form a lasting memory.

Attention↗
PubMed1995

Parietal contributions to visual feature binding: evidence from a patient with bilateral lesions.

Neurophysiologists have documented the existence of multiple cortical areas responsive to different visual features. This modular organization has sparked theoretical interest in how the "binding problem" is solved. Recent data from a neurological patient (R.M.) with bilateral parietal-occipital lesions demonstrates that the binding problem is not just a hypothetical construct; it can be a practical problem, as rare as the selective inability to perceive motion or color. R.M. miscombines colors and shapes even under free viewing conditions and is unable to judge either relative or absolute visual locations. The evidence suggests that a single explanation--an inadequate spatial representation--can account for R.M.'s spatial judgment and feature-binding deficits.

Cerebral Infarction↗
PubMed1994

Attention and apparent motion.

Two dissociations between short- and long-range motion in visual search are reported. Previous research has shown parallel processing for short-range motion and apparently serial processing for long-range motion. This finding has been replicated and it has also been found that search for short-range targets can be impaired both by using bicontrast stimuli, and by prior adaptation to the target direction of motion. Neither factor impaired search in long-range motion displays. Adaptation actually facilitated search with long-range displays, which is attributed to response-level effects. A feature-integration account of apparent motion is proposed. In this theory, short-range motion depends on specialized motion feature detectors operating in parallel across the display, but subject to selective adaptation, whereas attention is needed to link successive elements when they appear at greater separations, or across opposite contrasts.

Adaptation, Ocular↗
PubMed1992

The reviewing of object files: object-specific integration of information.

A series of experiments explored a form of object-specific priming. In all experiments a preview field containing two or more letters is followed by a target letter that is to be named. The displays are designed to produce a perceptual interpretation of the target as a new state of an object that previously contained one of the primes. The link is produced in different experiments by a shared location, by a shared relative position in a moving pattern, or by successive appearance in the same moving frame. An object-specific advantage is consistently observed: naming is facilitated by a preview of the target, if (and in some cases only if) the two appearances are linked to the same object. The amount and the object specificity of the preview benefit are not affected by extending the preview duration to 1 s, or by extending the temporal gap between fields to 590 ms. The results are interpreted in terms of a reviewing process, which is triggered by the appearance of the target and retrieves just one of the previewed items. In the absence of an object link, the reviewing item is selected at random. We develop the concept of an object file as a temporary episodic representation, within which successive states of an object are linked and integrated.

Adult↗
PubMed1992

Perceiving and re-perceiving objects.

A number of experiments exploring priming effects and automatization in the perception of novel objects are described, and a framework for understanding the benefits and costs of re-perceiving previously seen objects is proposed. The suggestion is that perceiving an object creates a temporary representation in an object file that collects, integrates, and updates information about its current characteristics. The contents of an object file may be stored as an object token and retrieved next time the object appears. This facilitates its re-perception when all of the attributes match and may impair it if some are changed. Thus, the world molds our minds to capitalize on earlier experiences but at the same time leaves us able readily to detect and represent any novel or unexpected objects and events.

Attention↗
PubMed1992

Automaticity and preattentive processing.

The characteristics of automatized performance resemble those of preattentive processing in some respects. In the context of visual search tasks, these include spatially parallel processing, involuntary calling of attention, learning without awareness, and time-sharing with other tasks. However, this article reports some evidence suggesting that extended practice produces its effects through different mechanisms from those that underlie preattentive processing. The dramatic changes in search rate seem to depend not on the formation of new preattentive detectors for the task-relevant stimuli, nor on learned abstracted procedures for responding quickly and efficiently, but rather on changes that are very specific both to the particular stimuli and to the particular task used in practice. We suggest that the improved performance may depend on the accumulation of separate memory traces for each individual experience of a display (see Logan, 1988), and we show that the traces differ for conjunction search in which stimuli must be individuated and for feature search where a global response to the display is sufficient.

Attention↗
PubMed1991

Search, similarity, and integration of features between and within dimensions.

Three experiments test the claim that conjunction search is difficult only because the target resembles each distractor, whereas the distractors are highly discriminable from each other. The results show that when similarity is controlled, there is an additional difficulty created by the need to conjoin features. In addition, a target with standard values (blue and vertical) is found more easily than targets with nonstandard values (e.g., violet and tilted). Similarity may result in shared components in the functional codes that represent the targets and the distractors. A hypothesis that is based on coarse coding of features values relates the difficulty of feature search with nonstandard targets to problems in coding conjunctions of features within dimensions. Consistent with this account, illusory targets are reported not only in the usual conjunction displays but also in displays containing different features that may share the same underlying components.

Attention↗
PubMed1990

Conjunction search revisited.

Search for conjunctions of highly discriminable features can be rapid or even parallel. This article explores three possible accounts based on (a) perceptual segregation, (b) conjunction detectors, and (c) inhibition controlled separately by two or more distractor features. Search rates for conjunctions of color, size, orientation, and direction of motion correlated closely with an independent measure of perceptual segregation. However, they appeared unrelated to the physiology of single-unit responses. Each dimension contributed additively to conjunction search rates, suggesting that each was checked independently of the others. Unknown targets appear to be found only by serial search for each in turn. Searching through 4 sets of distractors was slower than searching through 2. The results suggest a modification of feature integration theory, in which attention is controlled not only by a unitary "window" but also by a form of feature-based inhibition.

Adult↗
PubMed1990

Effect of surface medium on visual search for orientation and size features.

By using a visual search task, this study examined the encoding of orientation and size for stimuli defined in five different surface media: luminance, color, texture, relative motion, and binocular disparity. Results indicated a spatially parallel analysis of size and orientation features for all surface media, with the possible exception of binocular disparity. The data also revealed a search rate asymmetry in the orientation task for all media: Parallel or shallow search functions were obtained for oblique targets in vertical distractors, whereas steeper serial search functions were obtained for vertical targets in oblique distractors. No consistent asymmetry was found for the large and small targets in the size task. There seemed to be common principles of coding in all these different media, suggesting either a single analysis of shape features applied to a common representation or multiple analyses, one for each surface medium, with each extracting a similar set of features. The shared coding principles may facilitate the use of redundancy across media to reduce ambiguities in the locations and shapes of contours in the visual scene.

Adult↗
PubMed1990

Implicit and explicit memory for visual patterns.

The article reports an investigation of implicit and explicit memory for novel, visual patterns. Implicit memory was assessed by a speeded perception task, and explicit memory by a four-alternative, forced-choice recognition task. Tests were given either immediately after testing or 7 days later. The results suggest that a single exposure of a novel, nonverbal stimulus is sufficient to establish a representation in memory that is capable of supporting long-lived perceptual priming. In contrast, recognition memory showed significant loss over the same delay. Performance measures in the two tasks showed stochastic independence on the first trial after a single exposure to each pattern. Finally, a specific occurrence of a previously studied item could be retrieved from explicit memory but did not affect the accuracy of perception in the implicit memory test. The results extend the domain of experimental dissociations between explicit and implicit memory to include novel, nonverbal stimuli.

Consciousness↗