Search PubMed⌕ Search

Biomedical subjects

A Treisman

Publications and source records attributed to A Treisman.

12 recordsLinked to original sources
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↗
PubMed1986

Illusory words: the roles of attention and of top-down constraints in conjoining letters to form words.

When attention is divided among four briefly exposed syllables, subjects mistakenly detect targets whose letters are present in the display but in the wrong combinations. These illusory conjunctions are somewhat more frequent when the target is a word and when the distractors are nonwords, but the effects of lexical status are small, and no longer reach significance in free report of the same displays. Search performance is further impaired if the nonwords are unpronounceable consonant strings rather than consonant-vowel-consonant strings, but the decrement is due to missed targets rather than to increased conjunction errors. The results are discussed in relation to feature-integration theory and to current models of word perception.

Adolescent↗
PubMed1985

Search asymmetry: a diagnostic for preattentive processing of separable features.

The search rate for a target among distractors may vary dramatically depending on which stimulus plays the role of target and which that of distractors. For example, the time required to find a circle distinguished by an intersecting line is independent of the number of regular circles in the display, whereas the time to find a regular circle among circles with lines increases linearly with the number of distractors. The pattern of performance suggests parallel processing when the target has a unique distinguishing feature and serial self-terminating search when the target is distinguished only by the absence of a feature that is present in all the distractors. The results are consistent with feature-integration theory (Treisman & Gelade, 1980), which predicts that a single feature should be detected by the mere presence of activity in the relevant feature map, whereas tasks that require subjects to locate multiple instances of a feature demand focused attention. Search asymmetries may therefore offer a new diagnostic to identify the primitive features of early vision. Several candidate features are examined in this article: Colors, line ends or terminators, and closure (in the sense of a partly or wholly enclosed area) appear to be functional features; connectedness, intactness (absence of an intersecting line), and acute angles do not.

Adult↗