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Biomedical subjects

J T Enns

Publications and source records attributed to J T Enns.

33 records · Page 2Linked to original sources
PubMed1995

The box alignment illusion: an orientation illusion induced by pictorial depth.

In four experiments, observers attempted to align two sets of oblique edges to parallel. The contexts for these alignments included lines in isolation (2-D control), lines embedded in orthogonal drawings of same-oriented and different-oriented boxes (3-D objects), and each of these viewed against backgrounds depicting strong linear perspective (3-D backgrounds). A consistent distortion was observed in the alignments of different-oriented boxes relative to control lines, indicating that the parallel lines in these stimuli appeared to diverge toward the top of the picture. Furthermore, this box alignment illusion decreased with interstimulus distance, whereas alignment distortions in control lines and same-oriented boxes increased with distance. Viewing the stimuli against 3-D backgrounds produced a dramatic reversal of the illusion, with control lines now appearing to converge more than the boxes. These results suggest that the illusion reflects basic processes involved in pictorial depth perception.

Adult↗
PubMed1994

The development of selective attention: a life-span overview.

This paper outlines research on selective attention within a life-span developmental framework. Findings obtained in both the infancy-child and adulthood-aging literatures are reviewed and discussed in relationship to four aspects of selective attention: orienting, filtering, search, and expecting. Developmental consistencies and inconsistencies are identified and integrative theories are evaluated. Although a single theory is unlikely to accommodate the diverse patterns of age effects, emergent themes are identifiable nonetheless and the essential ingredients of a life-span theory of attentional development are enumerated. Directions for future research and theory are suggested.

Adolescent↗
PubMed1993

Size contrast as a function of conceptual similarity between test and inducers.

In four experiments, the effect of the semantic relationship between test and inducing stimuli on the magnitude of size contrast in an Ebbinghaus-type illusion was explored. In Experiments 1 and 2, the greatest illusion was found when test and inducing stimuli were identical in shape and differed only in size. Decreased size contrast was found when inducing stimuli were drawn from the same category as the test stimulus, but were not visually identical. Even less size contrast was found when inducing stimuli were from a near conceptual category, with the least effect when they were drawn from a completely different category. In Experiment 3, it was demonstrated that even if test and inducing stimuli are drawn with identical geometric elements, the size contrast illusion is greatly reduced if they represent apparently different conceptual categories (through the manipulation of orientation and perceptual set). In Experiment 4, any geometric or spatial confounds were ruled out. These results suggest that size contrast is strongly influenced by the conceptual similarity between test and inducing stimuli.

Adolescent↗
PubMed1992

Sensitivity of early human vision to 3-D orientation in line-drawings.

The modern "textbook" view of visual perception contains an inherent paradox. On the one hand, it claims that relatively simple edge-extraction processes requires a stimulus exposure of approximately 50 ms. On the other hand, it says that the identification of objects in photographs and line-drawings can be highly accurate with exposure durations as short as 100 ms. It is tempting to conclude that all the difficult work of perception occurs in the 50 ms that elapse between when these two tasks are accomplished. This article argues against this view, suggesting instead that much more than edge-extraction is accomplished by the early visual processes. To illustrate this view, a computational model is described that is capable of recovering the 3-D orientation of objects from some line-drawings, rapidly and in parallel. Data from recent visual search experiments with human observers are presented in support of this model and the implications of this view for the "textbook" view are discussed.

Female↗
PubMed1992

Visual search for direction of shading is influenced by apparent depth.

Recent reports of rapid visual search for some feature conjunctions suggested that preattentive vision might be sensitive to scene-based as well as to image-based features (Enns & Rensink, 1990a, 1990b). This study examined visual search for targets defined by the direction of a luminance gradient, a conjunction of luminance and relative location that often corresponds to object curvature and direction of lighting in naturalistic scenes. Experiment 1 showed that such search is influenced by several factors, including the type of gradient, the shape of the contour enclosing the gradient, and the background luminance. These factors were varied systematically in Experiment 2 in a three-dimensionality rating task and in a visual-search task. The factors combined interactively in the rating task, supporting the presence of an emergent property of three-dimensionality. In contrast, each factor contributed only additively to the speed of the visual-search task. This is inconsistent with the view that search is guided by specialized detectors for surface curvature or direction of lighting. Rather, it is in keeping with the view that search is governed by a number of "quick and dirty" processes that are implemented rapidly and in parallel across the visual field.

Attention↗
PubMed1991

Preattentive recovery of three-dimensional orientation from line drawings.

It has generally been assumed that rapid visual search is based on simple features and that spatial relations between features are irrelevant for this task. Seven experiments involving search for line drawings contradict this assumption; a major determinant of search is the presence of line junctions. Arrow- and Y-junctions were detected rapidly in isolation and when they were embedded in drawings of rectangular polyhedra. Search for T-junctions was considerably slower. Drawings containing T-junctions often gave rise to very slow search even when distinguishing arrow- or Y-junctions were present. This sensitivity to line relations suggests that preattentive processes can extract 3-dimensional orientation from line drawings. A computational model is outlined for how this may be accomplished in early human vision.

Attention↗
PubMed1990

Influence of scene-based properties on visual search.

The task of visual search is to determine as rapidly as possible whether a target item is present or absent in a display. Rapidly detected items are thought to contain features that correspond to primitive elements in the human visual system. In previous theories, it has been assumed that visual search is based on simple two-dimensional features in the image. However, visual search also has access to another level of representation, one that describes properties in the corresponding three-dimensional scene. Among these properties are three dimensionality and the direction of lighting, but not viewing direction. These findings imply that the parallel processes of early vision are much more sophisticated than previously assumed.

Computers↗
PubMed1989

A developmental study of covert orienting to peripheral visual cues.

Observers aged 6, 8, and 20 years participated in a speeded classification task designed to measure covert shifts of visual attention. On each trial observers responded to a target which appeared in one of three locations arrayed horizontally across the display. Three prestimulus cues were employed: neutral (the cue was present in all three possible target locations), unpredictable (the cue was present in the target location on a random basis), and predictable (the cue was present in the target location on 80% of the trials). There were four developmental findings: (1) Observers of all ages oriented attention automatically to the cued locations, (2) children processed targets in non-cued locations more slowly than adults, (3) only adults took advantage of the predictability of the cue, and (4) all age groups provided evidence that strategic orienting competes with response priming for cognitive resources. The implications of these findings for theories of attentional development are discussed.

Adult↗
PubMed1989

Relations between covert orienting and filtering in the development of visual attention.

This study examined a widely held assumption concerning the development of visual attention, namely, that different aspects of visual selectivity depend on common processing resources. Observers aged 5, 7, 9, and 24 years participated in a speeded classification task designed to examine the relations between covert shifts of attention and filtering. There were three important findings: (1) covert orienting and filtering share processing resources, (2) the ability to orient covertly to a target location and to filter competing information on the same trial became more efficient with age, and (3) 5 year olds were able to filter as efficiently as adults when target location was precued. The implications of these results for theories of attentional development are discussed.

Adult↗
PubMed1989

A developmental study of filtering in visual attention.

Children aged 4, 5, and 7 years and adults aged 20 years performed a speeded classification task designed to isolate several sources of interference in visual selective attention. On each trial, observers responded to 1 of 4 targets which were mapped to 2 responses. On some trials the targets were also flanked by distractor stimuli, which observers were asked to ignore. The interference measures examined the effects of attentional set, increases in feature number, increases in feature type, response competition, and stimulus generalization. All but 1 of the measures (stimulus generalization) produced reliable interference in the adult observers. However, only 2 of the measures (attentional set, increases in feature number) produced reliable interference in children. The implications of these findings for theories of attentional development are discussed.

Adult↗
PubMed1987

Selective attention in young children: the relations between visual search, filtering, and priming.

Previous studies of visual attention in children have used a wide variety of tasks to demonstrate that visual selectivity improves with age. A guiding assumption (often implicit) of this work is the existence of a single attentional resource that increases in capacity with development. The present study examined the relations between three components of tasks that are often used in developmental studies of attention: search, filtering, and priming. Additive factors logic was applied to a simple speeded classification task performed by subjects aged 4, 7, and 24 years. The results showed (1) improvements with age occurred in each of the three task components, (2) visual search was unrelated to filtering and priming, and (3) filtering and priming were related to one another in a capacity-sharing fashion. Implications of these results for developmental studies of attention and for theories of attention are discussed.

Adolescent↗
PubMed1987

da Vinci's window facilitates drawings of total and partial occlusion in young children.

When two or more objects are present in a scene, children 5 and 6 years of age rarely draw the scene such that one object totally or partially occludes another object. Instead they draw complete objects. The present study separated two components of drawing: perspective taking and graphic skill. Perspective taking was examined by comparing a free viewing condition with a restricted viewing condition in which a model could only be viewed through four apertures. Graphic skill was examined by comparing drawings requiring total occlusion with drawings requiring partial occlusion under both viewing conditions. Experiment 1 showed that 90% of 5- and 6-year-olds drew total occlusions under restricted viewing conditions but only 32% did so in the free viewing condition. Experiment 2 showed that drawings of partial occlusion were unaffected by viewing condition among 5-year-olds, but that restricted viewing increased the number of partial occlusions that 6-year-olds drew. Thus, failures of young children to draw occlusions have less to do with graphic skill than was previously thought. Instead, it is suggested that young children have a more general difficulty selecting one perspective and maintaining it over time.

Attention↗
PubMed1985

Developmental changes in selective and integrative visual attention.

School-aged children and adults performed two speeded classification tasks designed to examine the relation between selective and integrative aspects of visual attention. Stimuli consisted of two parentheses (Experiment 1) or two arrows (Experiment 2) separated by 0.5 to 16 degrees visual angle. In a selective attention task, observers classified stimuli on the basis of one of the two elements. Younger children experienced more interference when the elements were closely spaced than older children and adults. In an integrative attention task, stimuli were classified on the basis of both of the elements. Here age differences were most pronounced when elements were separated by large visual angles. These findings suggest that the ability to contract and expand the size of the attentional "spotlight" improves with age in the school years.

Adolescent↗