Social and nonsocial behaviors of adult rhesus monkeys after amygdalectomy in infancy or adulthood.

At 6 yr of age six female rhesus monkeys that had sustained bilateral amygdalectomy in infancy, and five intact controls, were transferred to an observation cage where behaviors were recorded while the monkeys were (a) alone, (b) paired with unfamiliar stimulus animals, and (c) paired with familiar monkeys from the opposite experimental group. The five adult controls then underwent amygdalectomy, and all tests were repeated with the infant- and adult-operated animals. Infant-operated monkeys changed behaviors more rapidly than did intact controls in social and nonsocial situations, and their activity levels were less modified after a 24-hr period in the observation cage. They were subordinate to intact controls but expressed less fear than did controls when briefly placed with an unfamiliar aggressive animal. Adult amygdalectomy produced many changes in behavior, but these aberrations were identical to those observed in like-age monkeys that had been amygdalectomized in infancy. Infant-operated monkeys demonstrated more behavioral deficits at 6 yr than they had earlier in life.     

Some exact conditional tests of independence forR ×C cross-classification tables

Exact conditional tests of independence in cross-classification tables are formulated based on the ² statistic and statistics with stronger operational interpretations, such as some nominal and ordinal measures of association. Guidelines for the table dimensions and sample sizes for which the tests are economically implemented on a computer are given. Some selected sample sizes and marginal distributions are used in a numerical comparison between the significance levels of the approximate and exact conditional tests based on the ² statistic.The authors are grateful for the suggestions of the referees and for computer funding provided by the Northeast Regional Data Center at the University of Florida.     

Spatial and contextual factors in beginning reading: Evidence for PSG-CSG complements to developing automaticity?

Two experiments were designed to examine the development of spatial and contextual sensitivity during early reading. Second and fifth graders read second- and fifth-grade level paragraphs that were either normally typed or had the spaces between the words filled. Both groups read the second-grade paragraphs and the normally typed paragraphs fastest, while the filled fifth-grade paragraphs were read slowest. The data were interpreted as providing evidence for a skill acquisition hierarchy that attempts to resolve contradictions previously reported by Hochberg (1970), while providing a good complement to LaBerge and Samuel’s (1974) notions of automaticity.     

The adjusted rand statistic: A SAS macro

A macro for calculating the Hubert and Arabie (1985) adjusted Rand statistic is presented. The adjusted Rand statistic gives a measure of classification agreement between two partitions of the same set of objects. The macro is written in the SAS macro language and makes extensive use of SAS/IML software (SAS Institute, 1985a, 1985b). The macro uses two different methods of handling missing values. The default method assumes that each object that has a missing value for the classification category is in its own separate category or cluster for that classification. The optional method places all objects with a missing value for the classification category into the same category for that classification.This study was supported in part by Individual National Research Service Award F32 DA 05283 from the National Institute on Drug Abuse.Requests for the Macro code can be sent via BITNET: CUSGPXH @ UCLAMVS. A copy of the macrocode can also be obtained by sending a stamped self-addressed mailer and a PC-DOS formatted floppy diskette to Paul Hoffman, 5628 MSA, UCLA, Los Angeles, CA 90024-1557.     

Spontaneous transfer of matching by infant chimpanzees (Pan troglodytes)

Four infant chimpanzees learned a matching-to-sample task when only two training stimuli were used. They then spontaneously transferred the matching concept to novel items, including three-dimensional objects and fabric swatches, without any experimenter-provided differential feedback. These results support the view that the matching concept is broadly construed by chimpanzees from the beginning and does not depend upon explicit training.     

Behavioral stress impairs long-term potentiation in rodent hippocampus

A number of hormones secreted from the pituitary-adrenal system during stress affect learning and memory processes. The phenomenon of hippocampal long-term potentiation (LTP) is viewed by many as a putative mechanism of memory storage and has proved a most valuable model for study of neuronal plasticity at the cellular level. The present study was conducted to investigate the possibility that stressful events which occur prior (in vivo) to the preparation of brain slices may influence the electrophysiology of the in vitro hippocampal explant when tested for LTP. Adult male rats (Long-Evans male X Sprague-Dawley female) were pair-housed 1 week prior to testing. One animal in each pair was either placed in a restraining tube for 30 min and received no tail shocks (Restraint) or placed in a restraining tube and received tail shocks (1 microA, 1 s) every minute for 30 min (Restraint + Shock). The other animal in each pair was taken directly from the home cage and received no restraint or tail shock (Control). In vitro hippocampal slices were then prepared immediately from these animals according to standard methods. Our results demonstrate a marked impairment of LTP in hippocampal explants taken from rats exposed to stress. The significance of this result with respect to cellular mechanisms underlying the relationship between stress, cognition, and learning is discussed.     

Effects of hypnosis and imagery training on naming behavior in aphasia

The effects of hypnosis and imagery training on the naming behavior of three subjects with Broca's aphasia were investigated using a multiple baseline design across subjects. Treatment consisted of the induction of hypnosis, followed by guided imagery focused on the physical and functional attributes of stimulus objects. Measures of naming ability on both trained and untrained items were taken at baseline, after every training session, and a few hours after training each day. Measures were also taken of imagery ability, hypnotic susceptibility, and psychological state. Results indicated that treatment facilitated improvement in naming ability, over baseline level, for two subjects. In the case of the third subject, the verbal label was incorporated into the imagery procedure following 10 training sessions. Subsequently, this subject's naming behavior improved over baseline level. The results are discussed in terms of current theory and research in neuropsychology and cognitive psychology.