Strategies of semantic categorization in the cerebral hemispheres

Strategies of semantic categorization in intact cerebral hemispheres were studied in two experiments by presenting names of typical and atypical category instances to the left visual field (LVF) (right hemisphere) or to the right visual field (RVF) (left hemisphere). The results revealed that the typicality of instances had a large effect on categorization times in the LVF in both experiments, suggesting that the right hemisphere relies strongly on a holistic, similarity-based comparison strategy. In Experiment 1, the typicality effect was weaker in the RVF than in the LVF. In Experiment 2, a typicality effect in the RVF was observed for the "four-footed animal" category but not for the "bird" category. The hypothesis that the left hemisphere employs a strategy based on defining or necessary features is not supported by the observed typicality effect in the "four-footed animal" category. Instead, it is suggested that the left hemisphere may be able to categorize on the basis of prestored instance-category knowledge. When such knowledge is not available (e.g., as for four-footed animals), a similarity-based comparison strategy is employed by the left hemisphere.     

Reward dominance among children with disruptive behavior disorders

Investigated was a deficit in avoidance learning in situations of competing rewards and punishments in boys with behavior disorders. This learning style has been found to differentiate adults with psychopathy and controls and has been labeled reward dominance. The present study investigated the reward dominance paradigm in a group of 9- to 13-year-old boys with disruptive behavior disorders (N=21) and a normal control group (N=22). Subjects played four computer games programmed to provide the subject with a steadily decreasing ratio of rewards to punishments. Although the groups did not differ initially on the number of trials played, significant group differences emerged when measures of anxiety were included in the analysis. That is, boys with disruptive behavior disorders played more trials (reward dominance) only when the effect of anxiety was controlled. These findings are consistent with Gray's biobehavioral theory of personality and are also consistent with research indicating that anxiety is an important marker for a distinct subgroup of children with behavior problems.     

A note on dual scaling of successive categories data

Three methods for dual scaling of successive categories data are formulated. They are mathematically equivalent, and provide an appropriate technique to determine stimulus values and category boundaries on a joint scale, a problem that Nishisato's method (1980a) failed to handle. This study was supported by the Natural Sciences and Engineering Research Council of Canada (Grant No. A7942) to S. Nishisato. Comments on the earlier draft from anonymous reviewers were most helpful and much appreciated.     

Merging and modifying hypotheses on the emotional and cognitive effects of eye movements: The dopaminergic regulation hypothesis

The integration of hypotheses from Eye-Movement Desensitization and Reprocessing (EMDR) and Saccade Induced Retrieval Enhancement (SIRE), both of which have been met with considerable skepticism, may lead to significant gains in both domains. Cognitive accounts of EMDR, the orienting response (OR) and working memory (WM) hypotheses, and of SIRE, the interhemispheric interaction (IHI) and the top-down attentional control (TDAC) hypotheses, are discussed. The accounts show several blind spots and frictions, for instance, on re-imagining during EMs, on hemispheric lateralization, and on emotional influences of eye movements. The failure to consider these factors across and within domains may well explain the many disparate findings. This perspective aims to remove the artificial separation and seeks a theoretical integration of the domains. It combines elements of OR and TDAC into a new dopaminergic regulation hypothesis while replacing affective (i.e., positive vs. negative) by motivational mechanisms (i.e., fostering approach and recoding). EMs are posited to result in a short-latency, targeted release of dopamine, which is the central neuromodulator in approach tendencies. According to this hypothesis, the largest effects are obtained in individuals with collateralized eye dominance and dopamine dominance. Concrete suggestions are made to improve research conditions and therapeutic efficacy.     

The differences between cerebral dominance patterns in the speed and accuracy of information processing among university students

IntroductionThe subject of cerebral dominance has received great attention by researchers; however, there is a paucity of studies that have examined its relationship to information processing.ObjectiveThe current study aims to reveal the differences between the cerebral dominance patterns (left cerebral dominance, right cerebral dominance, integrated parallel cerebral dominance) in the speed and accuracy of information processing.MethodA sample of (182) volunteers university students, (mean age ± SD, 19.92 ± 2.76 years; range, 18–24 years; 68 male, 114 females). The Human Information processing survey was applied to the participants. Each subject was exposed to two elementary cognitive tasks (Stroop task and Eriksen flanker task). Each task included two experimental conditions: first, the congruent condition that reflects the automatic processing of information; second, the incongruent condition that reflects the controlled processing of information.ResultsThe results of the study revealed that there were no differences between the patterns of cerebral dominance in the speed and accuracy of information processing.ConclusionAlthough the relationship between cerebral dominance and information processing is not significant, we need more studies to examine this relationship in other samples and in other experimental conditions.     

Testing the reference-dependent model: an experiment on asymmetrically dominated reference points

Standard choice theory assumes choice to be independent of the point of reference. Based on a number of studies which challenge this assumption, Tversky and Kahneman have proposed a reference-dependent model which captures the influence of reference points on individual choice. If choice is reference-dependent, switching the reference point so that it is first dominated by x and then by y increases the likelihood of choosing y. Switching the location of an asymmetrically dominated reference point without altering the dominance relationship should also influence reference-dependent choice in a predicted manner. In this paper the reference-dependent model is tested in two experiments which focus on asymmetrically dominated reference points. The results of these experiments give further confirmation to the reference-dependent model. © 1998 John Wiley & Sons, Ltd.     

Effects of fluoxetine on play dominance in juvenile rats

In a series of three studies, we investigated the influence of a selective serotonin re-uptake inhibitor (fluoxetine) on the rough-and-tumble play of juvenile rats. In Experiment 1, both members of eight pairs of solitary-housed juvenile rats received either vehicle, 2.5, 5, or 10 mg/kg fluoxetine in a counterbalanced within-subject design 20 min before being allowed to play for 5 min periods on four successive test days. The 5 and 10 mg/kg pretreatments significantly reduced incidence of pins during play without affecting dorsal contacts. In Experiment 2, one member of each of 19 established play pairs received 5 mg/kg fluoxetine 20 min before play, while the other member received vehicle. Dominant rats showed no reduction in pins as a result of fluoxetine treatment, but subordinate rats who received fluoxetine exhibited significant reductions in pins. Subsequent dyadic analyses indicated that in pairs where the subordinate animal received fluoxetine, dominant animals maintained their pinning advantage over the 10 days of testing, but in pairs where the dominant animals received fluoxetine, this pinning asymmetry diminished. In Experiment 3, we replicated the above procedure with inexperienced play pairs, to control for the effects of prior social learning. Fluoxetine treatment (5 mg/kg) significantly reduced both pins and dorsal contacts in all treated rats. The results indicate that fluoxetine can reduce the playful pins of juvenile rats, but that prior social learning mediates the strength of these effects. © 1996 Wiley-Liss, Inc.     

Subordinate swordtail males escalate faster than dominants: A failure of the social conditioning principle

In previous studies we have shown that subordinate swordtail males (Xiphophorus helleri) direct more bites to their mirror image than dominants and, in confrontations with strange dominant males, approach the opponent more often during the pre-escalation period of fights. Consequently, we predicted that fights between two omega-males should escalate faster than fights between two alpha-males. Indeed, in omega-omega fights preescalation periods were shorter and biting rates were higher than in alpha-alpha fights before the fights escalated from the first retaliation bite onward. Another new observation was that in omega-alpha confrontations the first bite in the pre-escalation period was executed more often by the omega-male and there was also a tendency to bite more compared to the alpha-male in that stage of the encounters. We conclude that sub-ordinate males escalate faster and fight more offensively prior to escalation than do dominant males. The results cannot be explained by the “social conditioning principle.” On the ultimate level moderate costs of losing and high benefits of winning a fight, constraints on continued growth after maturing, short life-expectancy, and habitat saturation are probably factors promoting the offensive tactics of subordinate males. © 1993 Wiley-Liss, Inc.     

Comparison of hemispheric activation during mental word and rhyme generation using transcranial Doppler sonography

The Wada test is at present the method of choice for preoperative assessment of patients who require surgery close to cortical language areas. It is, however, an invasive test with an attached morbidity risk. By now, an alternative to the Wada test is to combine a lexical word generation paradigm with non-invasive imaging techniques. However, results of this approach are still not in complete agreement with the findings of the Wada test (r = .92; Knecht, Deppe, Ebner et al., 1998). We attempted to obtain a more distinct language lateralization with the development of a phonological rhyme generation paradigm based on pseudoword stimuli. To examine the predictive value of both paradigms we performed simultaneous bilateral functional transcranial Doppler ultrasonography on 19 right-handed male native German subjects. The rhyme generation condition produced a significantly stronger lateralization to the supposed hemisphere of language dominance than the classical word generation condition. The observed differences suggest that the rhyme generation paradigm is more robust in detecting hemispheric language dominance than other neuropsychological paradigms and might be most valuable for preoperative assessment of cortical language areas.