Clare Porac

The dominant eye.

The dominant eye has often been denned as the eye whose input is favored in behavioral coordinations in which only one eye can be used, the eye preferred when monocular views are discrepant, or the eye manifesting physiological or refractive superiority. Although its functional significance has not yet been ascertained, patterns of ocular dominance have been shown to be related to a large number of perceptual, performance, and clinical phenomena. The nature of these relationships has remained obscure due to the variety of alternative tests for and theoretical definitions of eye dominance.

A behaviorally validated self-report inventory to assess four types of lateral preference

Abstract A self-report battery for the assessment of hand, eye, foot and ear preference, which has been validated against behavioral tasks designed to measure the same four types of laterality, is presented. Data showing the concordance between the inventory and the behavioral tests for a sample of 171 individuals is given. The mean degree of concordance between the behavioral and the questionnaire items was 90%. Additional analyses revealed that both forms of measurement provide similar descriptions of both individual and population lateral preference patterns. This report offers the questionnaire battery as a convenient and useful tool for the measurement of the four most common indices of laterality.

Environmental factors in hand preference formation: Evidence from attempts to switch the preferred hand

We surveyed 650 young adults to assess both their current handedness behaviors and past attempts to shift their hand preference. We found that 73 (11.2%) individuals had experienced hand preference change attempts and 52 (8.0%) had undergone pressure to switch hand preference to the right. The likelihood that an individual had experienced pressure to change hand use was not related significantly to gender or to a number of familial factors. However, the success of the hand change varied with gender; females reported greater success in shifting their handedness.

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.

Relationship between birth order, birth stress, and lateral preferences: a critical review.

Reviews the literature examining the relationship between birth order, birth stress, and lateral preferences in nonclinical samples, with special emphasis on reports since 1971. The review found no evidence to relate birth order position to deviations from right-sidedness for either sex. More direct measures of birth stress indicated that deviations from right-handedness (particularly for male subjects), and also right-eyedness, were statistically related to specific birth stressors. It should be stressed, however, that all the relationships, including the significant ones, were very weak, accounting for less than 1% of the variance. When statistical significance was achieved, it was largely due to the huge sample sizes used in the meta-analyses. Methological and theoretical problems exist in the current literature, and we offer some suggestions to resolve them.

The effect of optical blur on visual-geometric illusions

Blur, due to optical aberrations in the eye, has been implicated in visual illusions for converging line arrays. Using 26 illusion variants, 2.5 diopters of optical blur was optically induced, resulting in increased illusory effects for the Poggendorff and several Mueller-Lyer variants, but not for the other configurations. Some limitations on conditions drawn from induced blur are discussed.

Rate of physical maturation and handedness

Early versus late physical maturation was measured in 713 females and 467 males using the onset of secondary sexual characteristics, age of menarche, and relative body size. Delayed rates of maturation were associated with an increased incidence of left‐handedness in both sexes.

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.

Structural and cognitive components in the Müller-Lyer illusion assessed via cyclopean presentation

Several levels of visual information processing contribute to the formation of visual geometric illusions. The present experiment attempted to separate the relative contributions of structural (physiologically based) and strategy (cognitively based) mechanisms in the formation of the Müller-Lyer illusion. A novel experimental procedure that combined Cyclopean stimulus presentation and illusion decrement was employed. The results indicated that approximately 47% of the observed illusion magnitude can be attributed to the involvement of structural factors, a result consistent with other studies that have used different experimental techniques to explore the same issue.

Is eye dominance a part of generalized laterality

The laterality of eye and limb do not appear to be generally correlated as measured in 160 observers using a graded index. Sex differences emerge indicating more consistent eye and limb preferences as well as stronger eye dominance scores in male subjects. In addition, better consistency is found for right-eye dominants than for left. This pattern of results permits some inferences to be made about the role of the environment in determining the dominant eye and hand.