Differential hemispheric mediation of nonverbal visual stimuli.

Studies employing schematic faces of three features explored the role of the left hemisphere as an analytic processor in difficult discriminations and the role of the right hemisphere in easy gestalt matches. In a discrimination task, the successively presented members of a stimulus pair differed in all three features. When both stimuli went to the same visual field there was a Visual Field X Judgments interaction; judgments same were processed faster in the left visual field. When a test stimulus differing on all three features from a previously memorized target face was matched to the latter, both judgments same and different were made faster for stimuli in the left visual field. However, when the test stimulus and the memory items differed on only one feature the right field proved superior for both judgments same and different.     

Phonological mediation in visual masked priming: evidence from phonotactic repair

In a series of 4 experiments, the authors show that phonological repair mechanisms, known to operate in the auditory modality, are directly translated in the visual modality. This holds with the provision that printed stimuli are presented for a very brief duration and that the effect of phonological repair is tested after a delay of some 100 ms has elapsed after that presentation. The case of phonological repair chosen to exemplify the parallelism between print and speech is the prosthesis of /e/ in utterances beginning with /s/ followed by a consonant in Spanish. Native speakers of Spanish hear a prothetic /e/ in auditorily presented pseudowords such as special (/speojal/, derived from "especial") as well as stuto (/stuto/, derived from "astuto"). It is shown here that they also hear that same vowel /e/ when presented with the printed pseudowords "special" and "stuto." This finding of a phonological repair effect in print has implications for the issue of phonological activation from print, as well as for the prelexical locus and mandatory nature of phonological repair mechanisms in general.     

Perceptual versus postperceptual mediation of visual context effects: Evidence from the letter-superiority effect

Two experiments demonstrated letter-context effects that cannot easily be accounted for by post-perceptual theories based on structural redundancy, figural goodness, or memory advantage. In Experiment 1, subjects identified the color of a letter fragment more accurately in letter than in nonletter contexts. In Experiment 2, subjects identified the feature presented in a precued color more accurately in letters than in nonletters. We argue that these effects result from top-down perceptual processing.     

Intrahemispheric sex differences in the functional representation of language and praxic functions in normal individuals

Kimura (1980, The Behavioral and Brain Sciences, 3, 240-241; 1983, Canadian Journal of Psychology, 37, 19-35; 1987, Canadian Psychology, 28, 133-147) recently proposed that there are intrahemispheric sex differences in the organization of particular language and praxic functions such that in females these functions are more focally represented. This hypothesis, as well as supporting data, was derived from research with brain-injured subjects. The purpose of the present study was to test the utility of using dual-task methodology for investigating sex-related variation in intrahemispheric functional organization in normal individuals. Women were found to show greater interference than men on concurrent tasks of language and right-hand finger tapping. In support of Kimura's model, the present findings yielded evidence suggestive of intrahemispheric sex differences in the "functional distance" between language and praxic functions within the left hemisphere of normal individuals.     

Intrahemispheric differentiation of vowels: Principal component analysis of auditory evoked responses to computer-synthesized vowel sounds

Auditory evoked brain responses (AER) were recorded in response to a series of synthesized vowel sounds which varied in formant bandwidth. Multivariate analyses indicated that changes in AER component structure recorded from different scalp regions over both hemispheres varied as a function of different vowel sounds and formant bandwidth. No interhemispheric differences in scalp AER distributions were noted.     

Preference for and effects of variable-as opposed to fixed-reinforcer duration

Pigeons were trained on multiple schedules in which a fixed number of pecks produced either a fixed or a variable period of access to food, the average variable-duration reinforcement equalling the fixed. Pecking rates were generally higher during the variable-duration component. Subsequent performance on concurrent schedules revealed an initial preference for variable-duration reinforcement for all subjects; for most subjects, this preference was sustained. For one subject, the average variable duration was gradually reduced to half the fixed duration: continued preference for the variable component resulted in a loss of up to 30% of available reinforcement time. A return to multiple schedules with unequal pay-off shifted the preference to the greater fixed duration, and this preference was maintained even when the variable duration was again raised to equal the fixed duration. For the remaining subjects, the initial variable-duration preference on concurrent schedules was gradually replaced by a side preference. When the range of variable durations was varied, keeping the average variable duration equal to the fixed, the occasional longer reinforcers sustained a preference for variable-reinforcer durations for three of the four subjects.     

Physiological mediation of attitudinal responses.

A study was undertaken to try to ascertain the best model of the relationship between stimuli, physiological responses, and attitudes. Subjects were asked to indicate their attitudes toward various nations after having received various bogus information about how they responded physiologically to the stimuli. The results indicate the following: (a) In general, attitudes appear to be physiologically mediated; (b) physiological mediation of attitudes is strongest when prior knowledge about the stimuli is low but is independent of prior attitudes about the stimuli; (c) bogus physiological feedback does not seem to be verbally mediated; and (d) the most fruitful distinction between types of bogus feedback is between any feedback versus no feedback, not between change versus no change or between increase versus decrease in response.