Right Hemisphere Activation during Indirect Semantic Priming: Evidence from Event-Related Potentials

Healthy subjects performed a lexical decision task in a semantic priming paradigm while event-related potentials (ERPs) were recorded from 64 channels. Semantic distance between prime and target was varied by including directly, indirectly, and nonrelated word pairs. At centro-parietal electrodes an N400 to nonrelated pairs was elicited bilaterally which was sensitive only to direct, but not to indirect semantic priming. These N400 priming effects were mirrored by the RT data. At inferior fronto-temporal sites directly related words showed ERP priming effects over both hemispheres. However, indirectly related words only elicited ERP priming effects over the right hemisphere. These results support the hypothesis that the right hemisphere semantic system is involved in processing of remote semantic information.     

Limited translation invariance of human visual pattern recognition

Visual object recognition is considered to be largely translation invariant. An earlier study (Foster & Kahn, 1985), however, has indicated that recognition of complex novel stimuli is partially specific to location in the visual field: It is significantly easier to determine the identity of two briefly displayed random patterns if both stimuli are presented at the same, rather than at different, locations. In a series ofsame/different discrimination tasks, we characterize the processes underlying this “displacement effect”: Horizontal and vertical translations are equally effective in reducing performance. Making the task more difficult by increasing pattern similarity leads to even higher positional specificity. The displacement effect disappears after rotation or contrast reversal of the patterns, indicating that positional specificity depends on relatively low levels of processing. Control experiments rule out explanations that are independent of visual pattern memory, such as spatial attention, eye movements, or retinal afterimages. Positional specificity of recognition is found only forsame trials. Our results demonstrate that position invariance, a widely acknowledged property of the human visual system, is limited to specific experimental conditions. Normalization models involving mental shifts of an early visual representation or of a window of attention cannot easily account for these findings.     

Hegel und das Problem des Anfangs der griechischen Philosophie

Ohne Zusammenfassung     

Reaction time to different wavelengths at various luminances

The present investigation is concerned with determining whether or not differences in the reaction times exist in a human subject’s responses to 6 different wavelengths equated at 5 levels of luminance. The heterochromatic matching was done by the method of flicker photometry and checked by the method of direct comparison. Simple reaction time, the time interval starting with the presentation of a visual stimulus and terminating in a manual response, was used as the method of determining the latencies for the establishment of equal sensory effects for the different wavelengths. Monocular viewing of the stimuli was used by two subjects and reaction times are determined over a luminance range of 5.2 log units around a central value of I millilambert. The results indicated that simple reaction time is inversely related to stimulus luminance. There were no differences in the reaction times to the different wavelengths at the four highest luminance levels; at the lowest luminance level, the wave-lengths fan out in a manner that is in line with the classical data of vision. In other words, the visual functions obtained with simple reaction time parallel certain well-known visual functions in intensity discrimination, flicker and visual acutty-the results may be accounted for by the Duplicity Theory of vision.     

Validation of a category system for arguments in conflict discourse

Theories of individuation predict systematic differences in argumentative behavior between adolescent girls and their mothers. In order to reveal the nature and functions of this kind of discourse, two studies were carried out on 110 mother-daughter pairs. The second study (n=80) replicated and extended the first study (n=30) on an independent sample. The mother-daughter pairs were asked to discuss a subject that had recently been at issue between them. To assess the argumentative behavior, a category system was developed that reflects the functional character of utterances in discourse. The aim of the research was to test the reliability and validity of the category system. Daughters are assumed to verbalize their own needs and preferences to increase the differences to the mother, and to weaken or reject the mother's arguments in an effort to resist control. Mothers, on the other hand, are supposed to exert control over the behavior of their daughters but do so within bounds of mutuality. This should lead to verbal initiatives and attempts to explain, support and modify their positions and arguments. The data showed high reliability of the categorization of arguments. The categories also differentiated between mothers and daughters. Daughters were more likely to try to weaken and reject (and accept) the mother's arguments and to state preferences while mothers tried to support and explain their positions and to retain control by initiating questions and arguments to which the daughters responded.     

Are selective adaptation and contrast effects really distinct?

Although there is evidence that selective adaptation and contrast effects in speech perception are produced by the same mechanisms, Sawusch and Jusczyk (1981) reported a dissociation between the effects and concluded that adaptation and contrast occur at separate processing levels. They found that an ambiguous test stimulus was more likely to be labeled b following adaptation with [pha] and more likely to be labeled p following adaptation with [ba] or [spa] (the latter consisting of [ba] preceded by [s] noise). In the contrast session, where a single context stimulus occurred with a single test item, the [ba] and [pha] contexts had contrastive effects similar to those of the [ba] and [pha] adaptors, but the [spa] context produced an increase in b responses to the test stimulus, an effect opposite to that of the [spa] adaptor. One interpretation of this difference is that the rapid presentation of the [spa] adaptor gave rise to "streaming," whereby the [s] was perceptually segregated from the [ba]. In our experiment, we essentially replicated the results of Sawusch and Jusczyk (1981), using procedures similar to theirs. Next, we increased the interadaptor interval to remove the likelihood of stream segregation and found that the adaptation and contrast effects converged.     

Eurocommunist recognition of fundamental rights and its limits

Studies in East European Thought -