Tool use by chimpanzees (Pan troglodytes) of the Arnhem Zoo community

Abstract: Chimpanzees have a large repertoire of tool-use behaviors. This study reports on the variety and the extent of tool use exhibited by the chimpanzees of the Arnhem Zoo community in The Netherlands, living in an enriched captive setting since 1971. The use of tools by 29 chimpanzees aged from 0 to 37 years was observed. We identified 13 types of tool use comparable to those found in the wild. Some of these types of tool use seem to be specific to this community, and can be explained by the ecological characteristics of this captive setting. Chimpanzees started to use tools from the age of 2 years. Young chimpanzees, from 5 to 9 years old, showed a greater repertoire of tool use than infants and adults. All types of tool use in the community have appeared by the age of 10, the age of puberty for chimpanzees. Multivariate analysis was applied for the 29 individuals by 13 types of tool use in a one-zero matrix. The results show two major categories of tool use, one in a practical or substantial context and the other in a nonpractical or play context. The subjects clustered into groups reflecting developmental stages, although there are great individual differences. In conclusion, this captive community provides a unique opportunity to clarify the details of tool use by chimpanzees.     

An application of a discriminant analysis, based on the weighted H-index—a reanalysis

Abstract.— A discriminant-analysis method for dichotomized data, based on the weighted H -index as the similarity measure between two persons, is introduced. The weight assigned each item is a strictly increasing function of the absolute value of its D -estimate. Here, only power functions are used. The method which is called the WHIDD-analysis, is applied to some clinical data (Jonsson, 1975). The power of 3 produces a correct classification of all 32 persons in the validation group.     

Practice and Training in Family Therapy: A Known Group Study

The present study reports on a comparative survey of the belief and action systems of graduates who had been intensively trained in one of three of the major models of family therapy: Bowenian, communications, and strategic. An analysis of the factor-analyzed assumptions (belief system) and style (action system) items showed consistently greater divergence among the three models than convergence, as well as a remarkable synchronicity between the respective literature on these three models and their implementation, as represented by family therapists intensively trained in each model. A comparison of the present study's findings with previous research strongly supports the potency of formal and intensive training for developing adherents of a particular model and suggests that the distinctiveness of each model needs to be more fully developed in preference to premature attempts to develop generic or inclusive models that may become internally inconsistent and therefore difficult to operationalize in practice.     

Subitizing and counting processes in young children

Children attending the first grade in school were instructed to tell the number of dots (1–9) presented on a screen. The response latencies were related to the number of dots by two different linear relations for each subject. The first of these had a slope of about 0.1 sec/dot, was applicable for the encoding of 1–3 dots, and was taken as an indication of a subitizing process. The second linear relation was applicable for 5–9 dots and had a slope of about 1.0 sec/dot reflecting the speed of a counting process. The average intersection between the functions was located at 3.22 dots. The results were compared with earlier investigations of adult subjects who on the average subitize 6 dots and count 1 dot in about 0.4 sec. It was subitizing process being higher for adults. If the encoding of a stimulus has not been terminated within about 1.5 sec for children and adults the stimulus has instead to be identified in either a counting or an estimating process.     

Bandura's theory of self-efficacy: A set of common sense theorems

Bandura's (1977) theory of self-efficacy is translated into non-technical language and is shown to consist of logically necessary rather than empirically testable statements. As an alternative to the dominant empiricist view, it is argued that valid theories in psychology are explications of conceptual relationship imbedded in ordinary language (common sense). This conceptual network is anterior to both observation and theorizing. The analogy between the tasks of pre-Euclidean geometry and contemporary psychology is explored. The tasks are seen as involving explication of our implicit concepts of respectively space and people. One consequence of the stated view is that much psychological research is pointless since it attempts to verify logically necessary statements by empirical methods.     

Length of the postfeedback interval and learning of probabilistic inference tasks

Learning of negative linear and J-shaped cue-criterion relations in single-cue learning tasks was studied in an experiment which varied the length of the postfeedback interval. Contrary to the predictions from a hypothesis construction model assuming that subjects construct hypotheses from the data provided by the task, there was no effect of the postfeedback interval. The results were interpreted to mean that the subjects' constructions are based on elements stored in memory, rather than on data from the task.     

The development of risk acceptance and moral valuation

The relationship between acceptability of risks and moral valuation of risky activities was investigated in children, 10–16 years old. It was found that all age groups exhibited a strong correlation between the two dimensions of risky activities. Older children were more tolerant of risk taking than younger children. Individual actions were judged in a more lenient manner than collective actions. Girls tended to be more morally condemning towards risk taking, but the youngest girls were not less prone to accept risks than boys. General measures of moral development according to Piaget and Kohlberg were not associated with perceived acceptability of risk or the judged morality of risky activities but relations were found between risk taking and assertiveness and perceived freedom, which were the most important factors in accounting for risk and morality attitudes.