Malthus's Essay on Population: the facts of "super-growth" and the rhetoric of scientific persuasion

For the Malthusian theory of population to be accepted as "scientific," it was essential that the theory be established on wide empirical evidence. A close examination of the "facts" provided by Malthus, however, shows that many of his crucial facts are based on distortions of the available evidence. Malthus was probably aware of much of this weakness, but for rhetorical reasons he persisted with the sandy empirical foundations from which he began.     

Leadership skills and helpful factors in self-help groups

The effects of training on leadership skills and group processes in cancer and anorexic self-help groups are investigated. Three components of the study are reported. Firstly, an observational case-study of each type, of group was conducted to investigate the nature of the leadership input. Secondly, a Self-Help Questionnaire based on Lieberman's classification of leadership skills was administered to members of eight self-help groups to compare the experiences of groups with trained and untrained leaders. Thirdly, group members completed a Helpful Factors Questionnaire based on Yalom's analysis of group processes. The observational case-study revealed significant differences between the trained and untrained leaders in that, unlike the trained leader, the untrained leader clearly dominated the group. Results from the Self-Help Questionnaire showed that trained leaders scored higher on Caring and Emotional Stimulation but lower on Attribution of Meaning. Member satisfaction, however, was similar in the two types of group. Results from the Helpful Factors Questionnaire showed that most of the helpful factors were seen similarly by the two types of group, though differences were found concerning the relative rankings of both Guidance and Altruism. It is concluded that some degree of training of group leaders could be usefully incorporated into the self-help movement.     

Configurational information in face perception

A new facial composites technique is demonstrated, in which photographs of the top and bottom halves of different familiar faces fuse to form unfamiliar faces when aligned with each other. The perception of a novel configuration in such composite stimuli is sufficiently convincing to interfere with identification of the constituent parts (experiment 1), but this effect disappears when stimuli are inverted (experiment 2). Difficulty in identifying the parts of upright composites is found even for stimuli made from parts of unfamiliar faces that have only ever been encountered as face fragments (experiment 3). An equivalent effect is found for composites made from internal and external facial features of well-known people (experiment 4). These findings demonstrate the importance of configurational information in face perception, and that configurations are only properly perceived in upright faces.     

Relative effectiveness of three stimulus variables for locating a moving sound source

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was successful in indicating when a (stimulated) moving sound source passed an observer. These three variables were put into competition (with each indicating that closest passage occurred at a different time) in an effort to determine their relative importance. It was found that amplitude change dominated interaural temporal differences which, in turn, dominated the Doppler effect stimulus variable. The results are discussed in terms of two interpretations. First, it is possible that subjects based their judgements on the potential discriminability of each stimulus variable. However, because the stimuli used involved easily discriminable changes, subjects may instead have based their judgements on the independence of a stimulus variable from different environmental situation conditions. The dominance ordering obtained supports the second interpretation.