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Biomedical subjects

C Porac

Publications and source records attributed to C Porac.

At least 37 records · Page 2Linked to original sources
PubMed1986

Sighting dominance and egocentric localization.

Theories of the perception of visual direction use, either a hypothetical "projection center" midway between the two eyes, or the line of sight of the sighting dominant eye, as a reference point for egocentric localization. Seventy-five observers made judgments of the visual straight ahead. Their judgments varied as a function of both viewing condition and eye dominance. Judgments were biased toward the side of the viewing eye during monocular exposure, while binocular judgments were intermediate in their placement. Both monocular and binocular judgments were shifted in the direction of the sighting dominant eye, suggesting that the reference point for visual localization lies between the midpoint of the interocular axis and the line of sight of the sighting eye.

Depth Perception↗
PubMed1984

Writing hand posture and four indexes of lateral preference.

The relationship between writing hand posture and lateral preference for hand, foot, eye, and ear was examined in a sample of 3709 college undergraduates. A markedly different pattern of lateral preferences was observed in left-handed males and females as a function of hand posture. Left-handed male inverters displayed a tendency toward more leftward lateral preferences in all four indexes; while it was found that hand inversion during writing in left-handed females reflected, if anything, a tendency toward more rightward lateral preferences.

Ear↗
PubMed1983

The creation and reversal of the Müller-Lyer illusion through attentional manipulation.

A configuration is presented in which both the overestimated and the underestimated portions of the Müller-Lyer illusion are embedded. In free viewing no distortion of length occurs; however, overestimation or underestimation illusions can be produced by simple manipulation of the attentional set, thus demonstrating one cognitive component in the formation of the Müller-Lyer distortion.

Attention↗
PubMed1982

The relationship between birth stress and writing hand posture.

Variations in handwriting posture (inverted versus noninverted) were measured in 1203 individuals for whom birth histories, based upon retrospective maternal reports, were available. A history of birth complications was associated with an increased incidence of inverted handwriting posture. Effects interacted with sex and hand preference; the largest difference in handwriting posture between the birth-stressed and non-birth-stressed groups occurred in left-handers and in males.

Cesarean Section↗
PubMed1982

Monocular asymmetries in visual latency as a function of sighting dominance.

The speed of visual processing in the sighting-dominant and nondominant eyes was assessed using a simultaneity procedure in which an auditory target was set to apparently coincide with the onset of a visual stimulus. Under two types of monocular testing, the information from the sighting dominant eye was processed approximately 14 msec faster than the information from the nonsighting eye. These results suggest that the monocular channels are not completely interchangeable, and that response characteristics may vary as a function of sighting dominance.

Dominance, Cerebral↗
PubMed1980

Family patterns in four dimensions of lateral preference.

Hand, eye, foot, and ear preference were examined in a sample of 459 biologically related parent-offspring triads and 434 sibling pairs. Intercorrelations were computed using the side of preference as the dependent variables and then again using the absolute strength of the displayed preference irrespective of side. The directional analyses did not show strong patterns of familial similarities; however, relatives did tend to resemble each other in the degree of lateralization manifested. Maternal and paternal resemblance to offspring vary over the four indices of laterality, and there are some suggestions of sex-specific interactions. These results imply that genetic influence may operate to affect the degree of expressed preference, while the side of preference may not be genetically encoded. These findings also suggest that lateral preferences for limb and sense organ may not be due to a single causal mechanism.

Ear↗
PubMed1980

Birth factors and laterality: effects of birth order, parental age, and birth stress on four indices of lateral preference.

As an alternative to genetic theories of handedness, some theorists have offered an environmental mechanism, associated with birth stress, for the appearance of left-handedness. They suggest that brain damage as a result of birth difficulties can lead to a switch in hand preference from the right side to the left side. Consequently, one should find more left-handers in groups where the probability of the occurrence of birth stress is greater. Three studies are presented which explore the laterality of not only hand but also foot, eye, and ear, in a total of 5161 individuals, in an attempt to assess any relationship to birth stress. Maternal age seems to predict deviations from dextrality, dependent on the sex of the offspring, while paternal age and birth order do not. The use of a direct measure of conditions predisposing toward birth stress suggests that these results depend on prenatal or perinatal environmental trauma rather than chromosomal factors.

Adolescent↗