Reliability of test scores in nonparametric item response theory

Three methods for estimating reliability are studied within the context of nonparametric item response theory. Two were proposed originally by Mokken (1971) and a third is developed in this paper. Using a Monte Carlo strategy, these three estimation methods are compared with four classical lower bounds to reliability. Finally, recommendations are given concerning the use of these estimation methods.The authors are grateful for constructive comments from the reviewers and from Charles Lewis.     

Flicker contrast sensitivity in normal and specifically disabled readers

Temporal contrast sensitivity for counterphase flicker was determined for specifically disabled and normal readers to investigate whether the two groups differ in the functioning of their transient systems. In experiment 1, temporal contrast sensitivity was measured over a range of temporal frequencies with a spatial frequency of 2 cycles deg-1. Disabled readers were less sensitive than the control subjects at all temporal frequencies. In experiment 2, temporal contrast sensitivity was measured at a temporal frequency of 20 Hz over a range of spatial frequencies. Disabled readers were less sensitive than the controls at all spatial frequencies, with the differences between the groups increasing as spatial frequency increased. Both these findings are interpreted as supporting the hypothesis of a transient-system deficit in the visual systems of disabled readers.     

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.     

Subproblem learning: A misnomer

Among other things, K. J. Rust and T. S. Kendler (1987, Developmental Review, 7, 326–362) tested and disconfirmed the Tighes' independent subproblem learning hypothesis experimentally. The Tighes defended themselves by claiming that independent subproblem learning (ISPL) is a label, not a hypothesis and that our tests were invalid. In this reply we showed that ISPL is either an erroneous hypothesis or a misnomer because our tests were valid demonstrations that for young children the so-called “subproblems” are dependent rather than independent.