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At least 1,009 records · Page 56Linked to original sources
PubMed1998

Long-range twinkle induction: an achromatic rebound effect in the magnocellular processing system?

After viewing a blank region surrounded by a dynamic noise stimulus, viewers report the perception of prolonged dynamic twinkle in the unstimulated blank region. This twinkle aftereffect may be induced over long ranges in the visual field, up to 10 degrees from the edge of the noise in central vision. Our previous studies of the properties of this aftereffect suggested mediation by the magnocellular processing system. We therefore evaluated the properties predicted by the magnocellular hypothesis by varying the coloring, the temporal and the spatial frequency of the stimulus. No aftereffect could be induced by an equiluminant color stimulus or by luminance noise below the temporal frequency of 5 Hz. The aftereffect obtained by luminance noise above 5 Hz was stronger for larger inducing elements. These results are consistent with known properties of the magnocellular processing system.

Color Perception↗
PubMed2006

Visual memory for moving scenes.

In the present study, memory for picture boundaries was measured with scenes that simulated self-motion along the depth axis. The results indicated that boundary extension (a distortion in memory for picture boundaries) occurred with moving scenes in the same manner as that reported previously for static scenes. Furthermore, motion affected memory for the boundaries but this effect of motion was not consistent with representational momentum of the self (memory being further forward in a motion trajectory than actually shown). We also found that memory for the final position of the depicted self in a moving scene was influenced by properties of the optical expansion pattern. The results are consistent with a conceptual framework in which the mechanisms that underlie boundary extension and representational momentum (a) process different information and (b) both contribute to the integration of successive views of a scene while the scene is changing.

Color Perception↗
PubMed2005

Three-dimensional structure-from-motion selectivity in the anterior superior temporal polysensory area, STPa, of the behaving monkey.

Human and non-human primates are able to perceive three-dimensional structure from motion displays. Three-dimensional structure-from-motion (object-motion) displays were used to test the hypothesis that neurons in the anterior division of the superior temporal polysensory area (STPa) of monkeys can selectively respond to three-dimensional structure-from-motion. Monkeys performed a reaction time task that required the detection of a change in the fraction of structure in three-dimensional transparent sphere displays. Neurons were able to distinguish structured and unstructured three-dimensional optic flow. These cells could differentiate the change in structure-from-motion at stimulus presentation and when the animal was detecting the amount of structure in the display. Some of these neurons were also tuned for characteristics of the sphere stimuli. Cells were also tested with navigational motion and many were found to respond both to three-dimensional structure-from-motion and navigational motion. These results suggest that STPa neurons represent specific aspects of three-dimensional surface structure and that neurons within STPa contribute to the perception of three-dimensional structure-from-motion.

Animals↗
PubMed1997

Searching through subsets: a test of the visual indexing hypothesis.

This paper presents three experiments investigating the claim that the visual system utilizes a primitive indexing mechanism (sometimes called FINSTS; Pylyshyn, 1989) to make non-contiguous features directly accessible for further visual processing. This claim is investigated using a variant of the conjunction search task in which subjects search among a subset of the items in a conjunction search display for targets defined by a conjunction of colour and orientation. The members of the subset were identified by virtue of the late onset of the objects' place-holders. The cued subset was manipulated to include either homogeneous distractors or mixed distractors. Observers were able to select a subset of three items from among fifteen for further processing (Experiment 1); furthermore, a reaction time advantage for homogeneous subsets over mixed subsets was observed, indicating that more than one of the subset is selected for further specialized processing. The homogeneous subset advantage held for subsets of two to five items (Experiment 2), and the time required to process the cued subset did not increase with increased dispersion of the items (Experiment 3). These results support the basic claim of the indexing theory: the claim that multiple visual indexes are used in selecting objects for visual processing.

Adult↗
PubMed1995

Oculomotor responses with aviator helmet-mounted displays and their relation to in-flight symptoms.

Previous experiments have raised the possibility that abnormal oculomotor functioning could be the substrate for visual problems among aviators who use helmet-mounted displays. However, until the present investigation, no direct evidence linked the two. In our experiments, experienced Apache helicopter pilots, using the same helmet-mounted display that they use in flight, viewed Apache symbology and sensor imagery while we measured their accommodation and vergence eye movements in the laboratory. We found three circumstances that frequently occur in flight in which aviators with visual symptoms had different oculomotor responses than did asymptomatic aviators. Further work needs to be done to determine why symptomatic aviators respond differently from asymptomatic ones.

Accommodation, Ocular↗
PubMed1975

Underestimation of length by subjects in motion.

To check a prior observation, in the present experiment, subjects made estimates of the lengths of both the guidelines and the spaces between guidelines on automotive highways so the magnitude of the illusion could be more accurately determined. Ten males and ten females were individually tested at 0 and 60 mph. At 60 mph, spaces were estimated with an error of 85%; lines were estimated with an error of 72%. Combining data for both stimuli, an error of 78% results, which corresponds to underestimation by a factor of 4.67. This illusory effect is considerably greater than that of the moon illusion, considered by many the most powerful of the classical illusions.

Acceleration↗
PubMed1976

Amount of verbal information and ear-differences in 5- and 6-year old boys and girls.

Tow experiments were performed. The first was to determine the effects of varying the amount of information in verbal instructions presented monaurally on differences between ears and sex in 5-yr.-old boys and girls. Verbal instructions were given for the performance of a visual-motor task. The results indicated that the amount of verbal information affects ear-asymmetry in girls and not boys. The second experiment was performed to determine the effects of varying the amount of verbal information in verbal instructions presented monaurally on differences between ears, sexes, and reading ability of 6-yr.-old boys and girls. The findings indicated that above average readers performed better than below average readers. Ear-asymmetry was observed across sex and reading abilities for sentences containing 7 and 8 stimulus attributes. No ear-asymmetry was observed in sentences containg 9 stimulus attributes. The results appear to support the progressive lateralization hypothesis which states that ear-asymmetry is dependent on task conditions. The results also support sex differences in the development of brain lateralization.

Aptitude↗
PubMed1982

Effect of presentation time and Gestalt principles of proximity, similarity, and closure on perceptual accuracy.

The present study investigated Gestalt principles of proximity, similarity and closure. 32 subjects reproduced distances between dots and lines. Two stimulus exposure times were used. Time was significant for proximity, similarity, and closure. Type of distance estimated was significant for proximity and closure and the interaction of time and type of distance was significant for similarity. Most accurate estimations were consistently found for fast exposure times, and internal distances were estimated more accurately than external distances.

Adult↗
PubMed1986

Contribution of figural proportion, figural memory, figure-ground perception and severity of hearing loss to performance on spatial tests.

348 adolescents, 176 male and 172 female, were administered six different spatial tests. Awareness of figural proportion, figural memory, and figure-ground perception contributed significantly to performance on spatial visualization tests but not to performance on spatial orientation tests. Similarly, severity of hearing loss was correlated with scores on visualization tests but not on spatial-orientation tests.

Adolescent↗
PubMed1992

Response confidence and the Ponzo illusion.

The number of longer line judgments and the ratings of confidence in these judgements were significantly higher when the comparison line was located near the apex of the Ponzo wedge but only confidence ratings were affected by the orientation of the wedge (ns = 24 men, 24 women). Differences between the two measures suggest that perceptual and nonperceptual processes may be involved in the illusion.

Adolescent↗
PubMed1992

Symmetry in building block design for learning disabled and nonlearning disabled boys.

This study examined perceptual differences in symmetry with and without a model between 21 learning disabled boys with reading deficits and 28 learning disabled boys with deficits in mathematics. 55 nonlearning disabled boys served as controls. All boys were in Grades 3, 4, or 5. Without a model, all learning disabled boys built significantly more asymmetrical building block designs than nonlearning disabled boys. However, with a model, all learning disabled boys could imitate the model, but it took them longer to complete the task successfully. All boys appeared to have difficulty in modeling asymmetrical tasks, taking more time for task completion after seeing an asymmetrical model. This study suggests modeling perceptual tasks might be an effective teaching strategy for such children.

Attention↗
PubMed1989

Simultaneous sampling and length contrast.

The illusion of perceived line length produced by the parallel lines configuration reverses from assimilation to contrast with large spatial separation of the contextual and test lines (Jordan & Schiano, 1986). In the present experiment, we tested whether length contrast is produced by the sequential sampling of contextual and test lines or by the simultaneous sampling of the stimuli from a spatially distributed attentive field. Scanning instructions were manipulated such that one group of observers was encouraged to sample the lines sequentially, and a third group was given no specific scanning instructions. The data indicated that the reversal to length contrast is produced by simultaneous sampling of contextual and test lines. Implications for attentional descriptions of visual illusions are discussed.

Adult↗