PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Visual Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1986

Kinetic contours in infants' visual perception.

3-month-old infants' perception of "camouflaged" forms that are only visible when moving was studied. Displays were used in which figure and ground had an identical random dot texture, and no edge indicated the form of the figure. The form was invisible when stationary. Discrimination of 2 different forms was tested (a) when the forms were visible only through motion, and (b) when the forms appeared as stationary white figures on black ground. The babies discriminated the forms in both conditions. Furthermore, when infants were habituated to one of the moving forms and subsequently presented with the same and a new static form, they looked longer at the new form. This indicates that they recognized the static form as either the same or different from the moving form seen before, although the optical sources of information were completely different. At 3 months, infants can therefore effectively use kinetic information to organize the visual input in higher-order structures.

Discrimination Learning↗
PubMedDate not supplied

Audio-visual perception of compressed speech by profoundly hearing-impaired subjects.

For many people with profound hearing loss conventional hearing aids give only little support in speechreading. This study aims at optimizing the presentation of speech signals in the severely reduced dynamic range of the profoundly hearing impaired by means of multichannel compression and multichannel amplification. The speech signal in each of six 1-octave channels (125-4000 Hz) was compressed instantaneously, using compression ratios of 1, 2, 3, or 5, and a compression threshold of 35 dB below peak level. A total of eight conditions were composed in which the compression ratio varied per channel. Sentences were presented audio-visually to 16 profoundly hearing-impaired subjects and syllable intelligibility was measured. Results show that all auditory signals are valuable supplements to speechreading. No clear overall preference is found for any of the compression conditions, but relatively high compression ratios (> 3-5) have a significantly detrimental effect. Inspection of the individual results reveals that compression may be beneficial for one subject.

Adolescent↗
PubMed2003

Spatial-frequency spectra of printed characters and human visual perception.

It is well known that certain spatial frequency (SF) bands are more important than others for character recognition. Solomon and Pelli [Nature 369 (1994) 395-397] have concluded that human pattern recognition mechanism is able to use only a narrow band from available SF spectrum of letters. However, the SF spectra of letters themselves have not been studied carefully. Here I report the results of an analysis of SF spectra of printed characters and discuss their relationship to the observed band-pass nature of letter recognition.

Humans↗
PubMed1992

Visual space perception and visually directed action.

The results of two types of experiments are reported. In 1 type, Ss matched depth intervals on the ground plane that appeared equal to frontal intervals at the same distance. The depth intervals had to be made considerably larger than the frontal intervals to appear equal in length, with this physical inequality of equal-appearing intervals increasing with egocentric distance of the intervals (4 m-12 m). In the other type of experiment, Ss viewed targets lying on the ground plane and then, with eyes closed, attempted either to walk directly to their locations or to point continuously toward them while walking along paths that passed off to the side. Performance was quite accurate in both motoric tasks, indicating that the distortion in the mapping from physical to visual space evident in the visual matching task does not manifest itself in the visually open-loop motoric tasks.

Adult↗
PubMed1989

[Cognition for visual perception of a student apprentice of dental hygiene to the presence of a parent beside the dental chair for dental treatment].

With a view to finding out how the dental hygienist looks at and recognizes the changes in facial expression and behavior of a mother who is staying by her child just receiving dental care in the treating room, actions which the mother takes near her child were recorded and subjected to observation by a dental-hygienist apprentice. The eye movements of the apprentice were then recorded and analyzed, using the Visicon-Eye-Camera. The results obtained are as follows: 1. In all scenes of the test image, the subject closely observed the mother's face, the child's face and trunk and the dentist's face at a high frequency. 2. In all scenes of the test image, the subject tended to observe closely the mother's face in the former half of his observation and the child's face and the dentist's face in the latter half. 3. In a scene during which the mother looked anxious, the subject tended to look a longer time per observation. 4. In a scene during which there occurred only a change in the mother's expression, the subject frequently took the mother's face, the child's face or the dentist's face as his primary point of observation. 5. The scanning path of the subject was not influenced by a change in the mother's expression, but rather was influenced by the addition of new elements into the scene such as her grasping of the child's hands. 6. In case of the mother beginning to make a body movement, the subject frequently took the mother's face and her child's face as his primary point of observation. 7. The subject tended to make close observation of the dentist's face less frequently with more changes in the mother's behavior, suggesting his tacit cognition of the dentist being there. 8. The above results reveal that the dental hygienist is not visually influenced by the co-existence of a mother and her child just receiving dental care in the treating room if only she is looking at her child in a relaxed manner without any anxious expressions and attitudes.

Adult↗
PubMed2001

The effect of frequency on the visual perception of relative phase and phase variability of two oscillating objects.

Relative phase has been studied extensively as a measure of interlimb coordination. Only two relative phases, namely 0 degrees and 180 degrees, are stably produced at the preferred frequency (approximately 1 Hz). When frequency is increased, movement at 180 degrees becomes unstable and relative phase typically switches to 0 degrees, which remains stable at higher frequencies. The current study was designed to investigate the perception of relative phase and of phase variability. Observers viewed two circles moving rhythmically in a computer display. Mean phases varied from 0 degrees to 180 degrees in 30 degrees steps. Phase variability at each mean phase varied from 0 degrees to 5 degrees, 10 degrees, and 15 degrees phase standard deviation (SD). Frequency of oscillation was either 0.75 Hz or 1.25 Hz. One group of ten observers judged mean relative phase. Another group judged phase variability. As predicted, increase in frequency yielded an increase in perceived phase variability at 180 degrees mean phase and other mean phases, but not at 0 degrees mean phase. In contrast, increase in actual phase variability affected judgments of 0 degrees mean phase most strongly. A second control experiment showed that the frequency effects were not produced by changes in display durations or frames per cycle of oscillation. The results are consistent with those in studies of interlimb coordination and indicate that understanding of interlimb coordination requires further investigation of phase perception.

Adolescent↗
PubMed2005

Implicit exploitation of regularities: novel correlations in images quickly alter visual perception.

Viewing a set of two thousand images in which the contrasts of a central and a surrounding pattern were highly correlated increased the suppressive influence of the surround on the perceived contrast of the central pattern. The apparent increase in inhibition supports the operation of an anti-Hebbian mechanism between the two groups of cells excited by the patterns (one group by the central pattern and the other by the surround). According to this mechanism, inhibitory connections between nearby cells increase in efficacy according to a simple function of the correlations between the cells' activities.

Adaptation, Psychological↗
PubMed2006

The visual perception of plane tilt from motion in small field and large field: psychophysics and theory.

Subjects indicated the tilt of dotted planes rotating in depth, in monocular viewing, under perspective projection. The responses depended on the FOV (field of view) and on the angle W between the tilt and frontal translation (orthogonal to the rotation axis). Response accuracy increased with the FOV, and decreased with W. Our results support the processing of the second-order optic flow in all cases, but indicate that this flow is quantitatively small in small-field, leading to tilt ambiguities. We examine computational models based on the affine components of the optic flow to interpret our results.

Adult↗