Biomedical subjects

H Egeth

Publications and source records attributed to H Egeth.

17 recordsLinked to original sources

PubMed2000

Mixed reference frames for dynamic inhibition of return.

Reference frames mediating inhibition of return (IOR) in dynamic displays were investigated by comparing the effects of a cue in simple versus extended objects. Experiment 1 replicated S. P. Tipper, B. Weaver, L. M. Jerreat, and A. L. Burak's (1994) finding of location- and object-based IOR for boxes rotating about fixation. In Experiments 2 and 3, the boxes were replaced by two boomerang-shaped objects. Response times were slowed to all target locations across a cued object. They were also slowed to locations vacated by the uncued region of the cued object-evidence for a representation the authors call the "perceptual footprint." Whereas an object served as the medium for location-based IOR for B. S. Gibson and H. Egeth (1994), the environment served as the medium for object- and location-based IOR in Experiments 2 and 3. This suggests that (a) frames of reference may be considered hierarchically and (b) nesting of frames is context dependent.

Cues↗

PubMed1998

How does feature-based attention affect visual processing?

Five experiments are reported from which it is concluded that attending on the basis of a stimulus feature (e.g., red) does not directly affect the sensory quality of stimuli that possess that feature. Feature-based attention was manipulated in a visual search task by providing information about the probability that the target would possess a given feature (e.g., "The target has a 1.0 probability of being red when present.") Feature-based attention failed to aid performance under "data-limited" conditions (i.e., those under which performance was primarily affected by the quality of the stimulus) but did affect performance under conditions that were not data limited (Experiments 1-3). If attending to a feature had affected the sensory quality of stimuli, performance should have been aided under all conditions. Experiments 4 and 5 provided converging support for this conclusion.

Adolescent↗

PubMed1997

Perception without attention: evidence of grouping under conditions of inattention.

Many theories of visual perception assume that before attention is allocated within a scene, visual information is parsed according to the Gestalt principles of organization. This assumption has been challenged by experiments in which participants were unable to identify what Gestalt grouping patterns had occurred in the background of primary-task displays (A. Mack, B. Tang, R. Tuma, S. Kahn, & I. Rock, 1992). In the present study, participants reported which of 2 horizontal lines was longer. Dots in the background, if grouped, formed displays similar to the Ponzo illusion (Experiments 1 and 2) or the Müller-Lyer illusion (Experiment 3). Despite inaccurate reports of what the patterns were, participants' responses on the line-length discrimination task were clearly affected by the 2 illusions. These results suggest that Gestalt grouping does occur without attention but that the patterns thus formed may not be encoded in memory without attention.

Adolescent↗

PubMed1994

Inhibition of return to object-based and environment-based locations.

Inhibition of return (IOR) has been described in terms of two functional components. The location-based component is associated with descriptions of spatially fixed, environmental locations; the object-based component is associated with more abstract descriptions of spatially invariant objects. In the present study, we hypothesized that the location-based component may also be associated with descriptions of spatially invariant objects because, like environment-based descriptions, object-based descriptions have an intrinsic spatial structure. To test this hypothesis, we employed a computer-generated depiction of a brick that rotated in depth between the presentations of cue and target. The results of four experiments showed that IOR accrued to locations that remained fixed with respect to the brick as well as the environment, suggesting that both object-based and environment-based descriptions can influence location-based IOR.

Attention↗

PubMed1994

Inhibition and disinhibition of return: evidence from temporal order judgments.

In the present study the temporal order judgment (TOJ) task was used to investigate whether or not inhibition of return (IOR) affects perceptual processing. Previous failures to obtain IOR in the TOJ task have been taken to suggest that IOR does not affect perceptual processing (e.g., Maylor, 1985). The present study showed that IOR is modulated by the temporal disparity between successive targets as well as the relative order in which they appear at cued and uncued locations. Consequently, IOR affects TOJs in some conditions but not in others. The selective occurrence of IOR in the TOJ task provides converging support for the notion that IOR does affect perceptual processing, and also accounts for the previous failures to observe IOR in the TOJ task. Moreover, these and other results suggest that inhibitory processing at the cued location can be disinhibited when stimulation occurs at other locations.

Attention↗

PubMed1993

Nucleus basalis magnocellularis and attention: effects of muscimol infusions.

The basal forebrain is important in cognitive processing. Most studies have focused on the importance of this area in mnemonic processing. However, the nucleus basalis magnocellularis (NBM), which is a major component of the basal forebrain, may also be involved in attentional processes. Attention can influence the sensitivity of perceptual processes, as assessed by discriminability, or the selection of response strategies, as assessed by bias. This experiment examined whether temporary inactivation of the NBM, using the GABA agonist muscimol, would interfere with attention. Each rat was tested in a 2-choice reaction time (RT) task in which stimulus frequency was varied. RT and error rate increased, and discriminability decreased following muscimol infusions into the NBM. Bias was unchanged. The pattern of results provides evidence that the NBM is important in attention, and this influence of the NBM acts primarily on perceptual aspects of attention.

Animals↗

PubMed1992

Consequences of allocating attention to locations and to other attributes.

Simple reaction time to a light target may be lengthened when the light is preceded by a noninformative stimulus at the same location. This is known as inhibition of return. Does inhibition of return result if the relation between successive stimuli is defined in terms of color or orientation? Subjects pressed a key when a small square was displayed. In Experiments 1-3, location and color of the square were manipulated; there was inhibition of return based on location, but not on color. In Experiments 4-5, a confounding of color and luminance was eliminated, with no change in results. In Experiments 6-7, the background was composed of vertical stripes and the squares were composed of left- or right-oriented diagonal stripes. There was evidence of inhibition of return based on location, but not on orientation. These data support the idea that location is processed differently from other features.

Adult↗

PubMed1992

Expectancy and stimulus frequency: a comparative analysis in rats and humans.

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency. A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.

Animals↗

PubMed1991

Parallel versus serial processing in visual search: further evidence from subadditive effects of visual quality.

The authors propose a diagnostic for distinguishing between serial and parallel processing in visual search; it is based on testing for subadditive effects of a within-trial visual quality manipulation on target-absent trials. It was evaluated in 2 experiments wherein parallel and serial processing might be expected on the basis of previous work and was then applied to a more uncertain situation in a third experiment. The diagnostic indicates parallel processing of stimuli that differ from each other on a featural basis (Xs and Os) and canonical letters that differ in line arrangement (Ts and Ls) but serial processing when Ts and Ls are randomly rotated. These results form a coherent pattern that is understandable in terms of the literature on visual search, and thus they suggest that the diagnostic may be a useful addition to the methodology used to distinguish between serial and parallel processes.

Adult↗

PubMed1991

Further evidence for a time-independent shift of the focus of attention.

The separation between stimuli was manipulated in a same-different matching task. In Experiment 1, stimuli were upright Ts and/or Ls, whereas in Experiment 2, they were rotated Ts and/or Ls. In both experiments, mean reaction time (RT) for the same-different judgment did not increase as a function of interletter separation, suggesting either that the time needed to relocate attention was independent of distance, or that the stimuli were processed in parallel. These alternatives were tested in a third experiment, with a diagnostic for parallel processing proposed by Egeth and Dagenbach (1991). The diagnostic indicated that the rotated Ts and Ls in Experiment 2 were processed serially. If serial processing implies the utilization of attention, then the results of Experiment 2 suggest that relocation of attention is time-invariant with respect to distance.

Adult↗

PubMed1989

Does the identification of simple features require serial processing?

Several recent studies have shown performance decrements with increasing display size when background texture elements are present in a same-different feature discrimination task--a result that challenges the traditional notion that the identities of simple visual features are processed in parallel, preattentively. Four experiments are reported that explore the implications of these results. Experiment 1 replicates the recent studies but limits the generalizability of the results to small target numbers. Experiments 2 and 3 show that the observed performance decrements are not due to a serial or even limited-capacity, parallel process. Experiment 4 suggests that decision factors idiosyncratic to the use of texture elements in a same-different task are responsible for the effect. It is concluded that the identification of simple visual features proceeds in parallel, with unlimited capacity (i.e., preattentively).

Adolescent↗

PubMed1988