INDUCING VARIABILITY IN COMMUNICATIVE GESTURES USED BY SEVERELY RETARDED INDIVIDUALS

Handicapped individuals who have been taught spontaneous gesture requests often use only a small part of their vocabulary. Procedures to recover the unused part of this vocabulary have not been documented. This study was designed to identify procedures for increasing the proportion of gestures used spontaneously. Six mentally handicapped individuals served as subjects. After a baseline phase during which spontaneous gesture requests were reinforced, consequences were withheld for high-rate gesture requests. This led to an increase in different gesture requests. Although gesture requests did not return to baseline levels during a reversal condition, functional control was demonstrated by way of a multiple baseline across subjects. The absence of a reversal effect suggests enduring effects of the procedure.     

Local and global mechanisms of one- and two-dimensional orientation illusions.

One-dimensional (1-D) orientation illusions induced on a test grating by a tilted and surrounding 1-D inducing grating have a well-known angular function that exhibits both repulsion and attraction effects. Two-dimensional (2-D) orientation illusions are those induced on a test grating by 2-D image modulation, such as a pair of superimposed inducing gratings at different orientations, usually orthogonal (a plaid). Given the known angular functions induced by the plaid component gratings, two hypotheses were developed that predicted different plaid-induced illusion functions. Hypothesis 1 states that the 1-D component-induced effects simply add linearly; Hypothesis 2 states that there is an additional mechanism that responds to the virtual axes of mirror symmetry of the plaid and adds to the effect. The data of two experiments were consistent with the predictions from the second hypothesis but not the first. Possible neural substrates of mechanisms that extract axes of symmetry are discussed; it is suggested that such global symmetry axes may underlie the perceived orientation of complex shapes.     

The fear potentiated startle effect

A differential conditioning study examined whether an acoustic startle probe, presented during extinction of an aversively conditioned visual stimulus, potentiated the reflex eyeblink response in humans and whether this potentiation varied with the change in affective valence of the conditioned stimulus. Sixty college students were randomly assigned to view a series of two slides, depicting either unpleasant/highly arousing, unpleasant/moderate arousing, neutral/calm, pleasant/moderate arousing or pleasant/highly arousing scenes and objects (duration: 8 sec). During preconditioning (8 trials) and extinction (24 trials) acoustic startle probes (white noise bursts [50 ms; 95 dBA] were administered during and between slide presentation). During acquisition (16 trials) CS+ was reinforced by an electric shock. Startle response magnitudes significantly increased from preconditioning to extinction and were substantially larger to CS+. Conditioned startle reflex augmentation linearly increased with the pleasantness of the slides. Furthermore, subjects showed a greater post-conditioning increase of judged aversiveness to slides that they had previously reported to be more pleasant, exactly paralleling the startle reflex results.

     

Analysis of the components of disparity in Wilde's dot-row phenomenon

Summary In this study on Wilde's phenomenon (Wilde 1950) the two components of disparity, one of them processing displacement, and the other one apparent rotation, are analysed in terms of dependence on the disparity of the end-lines of the pattern (), and on the percentage of magnification (M) of one of the monocular patterns in relation to the other one. It was found that the component of disparity for displacement ' can be expressed as a linear regression equation '=–a+b.The component of disparity for rotation, expressed as a percentage of magnification effective for rotation (M) can be expressed as M=a–b₁+b₂M.It was concluded that the two components of disparity are processed through independent parallel channels, the processing of the component of disparity for displacement being the faster process, accounting for the larger part of the total disparity.     

Maximum likelihood estimation for Luce's choice model

A terminology for general choice models based on the choice axiom is given. It applies to all kinds of choice experiments, such as confusion choice experiments, paired comparisons, triadic comparisons, directional rankings, scores on binary test items, and others. Maximum likelihood estimation for such general choice models is considered. Conditions for the uniqueness of maximum likelihood estimates are given, and it is shown that the estimates can be derived by iterative proportional fitting. This offers the opportunity of a general test of the choice axiom for all kinds of choice experiments using the likelihood ratio. The estimation and testing procedure is applied to data from a form recognition experiment, reported by W. A. Wagenaar (Nederlands Tijdschrift voor de Psychologie, 1968, 23, 96–108).     

Sex differences in the association of math achievement with visual-spatial and verbal working memory: Does the type of math test matter?

Previous research on sex differences in mathematical achievement shows mixed findings, which have been argued to depend on types of math tests used and the type of solution strategies (i.e., verbal versus visual-spatial) these tests evoke. The current study evaluated sex differences in (a) performance (development) on two types of math tests in primary schools and (b) the predictive value of verbal and visual-spatial working memory on math achievement. Children (N = 3175) from grades 2 through five participated. Visual-spatial and verbal working memory were assessed using online computerized tasks. Math performance was assessed five times during two school years using a speeded arithmetic test (math fluency) and a word problem test (math problem solving). Results from Multilevel Multigroup Latent Growth Modeling, showed that sex differences in level and growth of math performance were mixed and very small. Sex differences in the predictive value of verbal and visual-spatial working memory for math performance suggested that boys seemed to rely more on verbal strategies than girls. Explanations focus on cognitive and emotional factors and how these may interact to possibly amplify sex differences as children grow older.     

Leader Network Centrality and Team Performance: Team Size as Moderator and Collaboration as Mediator

The social network perspective provides a valuable lens to understand the effectiveness of team leaders. In understanding leadership impact in team networks, an important question concerns the structural influence of leader centrality in advice-giving networks on team performance. Taking the inconsistent evidence for the positive relationship of network centrality and leadership effectiveness as a starting point, we suggest that the positive impact of leader centrality in advice-giving networks is contingent on team needs for leadership to meet communication and coordination challenges, which we argue are larger in larger teams. Developing our analysis, we examine the mediating role of member collaboration in the relationship of leader network centrality and team performance as moderated by team size. Based on a multi-source dataset of 542 employees and 71 team leaders, we found that leader centrality in advice-giving networks related positively to team performance in larger teams but negatively in smaller teams. Results supported the mediated moderation model via member collaboration in smaller teams, but not in larger teams.

     

Networks of happiness: applying a Network Approach to Well-Being in the General Population

Journal of Happiness Studies - Even though well-being can be seen as a multidimensional construct, made up of a variety of interacting aspects, most studies examine total scores on well-being...