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Biomedical subjects

K Kirsner

Publications and source records attributed to K Kirsner.

10 recordsLinked to original sources
PubMed1987

Are there different methods of lexical access for words presented in the left and right visual fields?

Visual field differences can arise from hemispheric specializations or perceptual asymmetries. Deciding which of the two is responsible for a particular visual field difference is a recurrent problem for researchers concerned with lateral asymmetries. In the present paper, the difficulties involved in interpreting visual field asymmetries are discussed as they apply to the Young and Ellis (1985) research on the interactive effects of word length and visual hemifield on the recognition of English words. We show that one of their critical results disappears when small changes are made to their experimental procedure. Our data demonstrate that the visual field differences Young and Ellis reported were the result of preceptual asymmetries rather than different methods of lexical access in the two cerebral hemispheres.

Adolescent↗
PubMed1986

Words and hemifields: do the hemispheres enjoy equal opportunity?

A common technique in research into cerebral asymmetry in both normal and clinical populations involves the use of lateralized visual displays. The validity of this approach depends on several generally implicit assumptions about the character of the cognitive processes involved. For example, when words are used as stimuli, cognitive processing is assumed to involve either "whole-word" or "ends-in" analysis. In this way, both hemispheres are assumed to have equal opportunities to recognize the word. These assumptions are critical, because if they are wrong, explanations based on established perceptual principles may provide a sufficient and more parsimonious explanation for hemifield asymmetries than hemispheric specialization theories. This point is developed and illustrated with particular reference to word recognition and classification. From a purely perceptual viewpoint, the right visual field advantage observed in tasks using word stimuli is to be expected given the presence of systematic biases in favor of initial characters or features of words and the relationship between retinal eccentricity and visual acuity. In other words, there is no need nor justification for a hemispheric account of visual field differences in such tasks. Some of the limiting conditions and theoretical implications of this argument are identified and discussed.

Dyslexia↗
PubMed1986

Behavioral or hemispheric asymmetry: is there a default option?

The presence of acuity gradients as a moderating variable in hemifield research is not in question. Their importance as a determinant of hemifield differences is unclear, however. The major issues are as follows. First, do vertical displays provide an appropriate control for the acuity gradient? Second, do the initial letters of a word play a critical role in word recognition, either in information-theoretic terms or because the lexicon is itself organized around access codes based on the initial letter or letters of words? Third, do behavioral and hemispheric accounts provide equally attractive explanations of Task Level X Visual Field interactions? Fourth, if the two accounts are equally attractive on empirical grounds, which is to be preferred? Each of these issues is addressed in this reply to M. P. Bryden's (1986, Brain and Cognition, 5, 362-368) and J. Hellige's (1986, Brain and Cognition, 5, 369-376) comments on our article (K. Kirsner & S. Schwartz 1986, Brain and Cognition, 5, 354-361).

Brain↗
PubMed1979

Visual persistence and code selection in short-term memory for letters.

Four experiments were conducted to examine temporal changes in visual and name codes and the relationship between them. Unlike earlier studies, the design included (a) several levels of visual similarity in addition to the conventional same case and different case conditions and (b) physical- as well as name-match tasks to provide direct evidence about subjects' retention of form information. The main results were as follows: First, the presence of multiple typefonts in the stimulus set does not eliminate convergence between the reaction time functions for the physical- and name-match conditions in a name-match task. Second, inclusion of a physical-match task, requiring subjects to retain form information, does not necessarily eliminate convergence in a primary, name-match task. When the secondary task does reduce convergence, however, the results suggest that it does this through its effect on the name-match function rather than on the physical-match function. Third, apart from difficulties with within-cluster typefont combinations, particularly at long interstimulus intervals, subjects can generally retain and use reliable information about letter form over the ISI range (.5--4.0 sec) used in the experiments. The results were thought to be consistent with the conclusion that convergence results from a combination of (a) a nonoptional decrease in the accessibility of the visual code as a function of increasing ISI and (b) an optional increase in the accessibility of the name code. Under ISI conditions at least, convergence cannot be attributed to either generation of a visual code of the alternative form of the target letter or to the absence of relevant form information.

Discrimination Learning↗