Response strength in extreme multiple schedules

Four pigeons were trained in a series of two-component multiple schedules. Reinforcers were scheduled with random-interval schedules. The ratio of arranged reinforcer rates in the two components was varied over 4 log units, a much wider range than previously studied. When performance appeared stable, prefeeding tests were conducted to assess resistance to change. Contrary to the generalized matching law, logarithms of response ratios in the two components were not a linear function of log reinforcer ratios, implying a failure of parameter invariance. Over a 2 log unit range, the function appeared linear and indicated undermatching, but in conditions with more extreme reinforcer ratios, approximate matching was observed. A model suggested by McLean (1991), originally for local contrast, predicts these changes in sensitivity to reinforcer ratios somewhat better than models by Herrnstein (1970) and by Williams and Wixted (1986). Prefeeding tests of resistance to change were conducted at each reinforcer ratio, and relative resistance to change was also a nonlinear function of log reinforcer ratios, again contrary to conclusions from previous work. Instead, the function suggests that resistance to change in a component may be determined partly by the rate of reinforcement and partly by the ratio of reinforcers to responses.     

Child Sleep Problems and Parental Depression: Testing a Risk and Resistance Model

Although extensive studies demonstrate a link between infant sleep problems and parental depression, limited research explores this relation in parents of primary school aged children. Using cross-sectional data, we investigated direct, moderating and mediating risk and resistance factors in the relation between child sleep problems and parental depressive symptomatology in a sample of 145 Australian parents of primary school aged children. Parents completed the children’s sleep habits questionnaire, the short temperament scale for children, the perceived stress scale and the depression sub-scale of the depression, anxiety and stress–short form. Correlational analyses confirmed bivariate relations between parental stress and parental depressive symptomatology, and between child sleep problems and parental depressive symptomatology. Multiple regression analyses identified parental stress as a mediator of the relation between child sleep problems and parental depressive symptomatology, and the approach component of child temperament as a moderator of the relation between child sleep problems and parental depressive symptomatology. Findings suggest that parents of children with sleep problems experience increased stress levels and increased levels of depressive symptomatology and may be at increased risk of depression if their child has a difficult temperament characterized by low approachability. Implications for clinical intervention and future research are discussed.     

Medical Students' Views on the White Coat: A South African Perspective on Ethical Issues

There is a debate regarding the use of the white coat, a traditional symbol of the medical profession, by students. In a study evaluating final-year South African medical students' perceptions, the white coat was associated with traditional symbolic values (e.g., trust) and had practical uses (e.g., identification). The coat was generally perceived to evoke positive emotions in patients, but some recognized that it may cause anxiety or mistrust. Donning a white coat generally implied a responsibility to the profession. For a few, without the coat, patients would not cooperate, resulting in some perceiving no need to be distinguished from qualified practitioners. There was thus some evidence of entitled (vs. earned) respect. In the light of the underresourced health care setting in which these students learn clinical medicine, we recommend that students be able to recognize the potential for unprofessional or unethical behavior. Students should also be able to identify role models.     

Emerging Understanding of Patterning in 4-Year-Olds

Young children have an impressive amount of mathematics knowledge, but past psychological research has focused primarily on their number knowledge. Preschoolers also spontaneously engage in a form of early algebraic thinking—patterning. In the current study, we assessed 4-year-old children's knowledge of repeating patterns on two occasions (N = 66). Children could duplicate and extend patterns, and some showed a deeper understanding of patterns by abstracting patterns (i.e., creating the same kind of pattern using new materials). A small proportion of the children had explicit knowledge of pattern units. Error analyses indicated that some pattern knowledge was apparent before children were successful on items. Overall, findings indicate that young children are developing an understanding of repeating patterns before school entry.     

Visual temporal processing in dyslexia and the magnocellular deficit theory: the need for speed?

A controversial question in reading research is whether dyslexia is associated with impairments in the magnocellular system and, if so, how these low-level visual impairments might affect reading acquisition. This study used a novel chromatic flicker perception task to specifically explore temporal aspects of magnocellular functioning in 40 children with dyslexia and 42 age-matched controls (aged 7-11). The relationship between magnocellular temporal resolution and higher-level aspects of visual temporal processing including inspection time, single and dual-target (attentional blink) RSVP performance, go/no-go reaction time, and rapid naming was also assessed. The Dyslexia group exhibited significant deficits in magnocellular temporal resolution compared with controls, but the two groups did not differ in parvocellular temporal resolution. Despite the significant group differences, associations between magnocellular temporal resolution and reading ability were relatively weak, and links between low-level temporal resolution and reading ability did not appear specific to the magnocellular system. Factor analyses revealed that a collective Perceptual Speed factor, involving both low-level and higher-level visual temporal processing measures, accounted for unique variance in reading ability independently of phonological processing, rapid naming, and general ability.     

When Seeing Is Not Believing: An Examination of the Mechanisms Accounting for the Protective Effect of Media Literacy on Body Image

Sex Roles - The present study aimed to explore the moderating role of three dimensions of media literacy on the relationship between media exposure and body dissatisfaction, mediated by thin-ideal...     

The Emergence of Narrative Identity

This paper reviews the current research on narrative identity. Narrative identity is quickly becoming accepted as a promising process approach to self‐development in a variety of fields, including developmental, clinical, cultural, personality, and social psychology. This paper reviews factors surrounding the emergence of narrative identity in adolescence, relations between narrative patterns and age and personality, as well as factors that are important to developing a coherent narrative identity, such as the emotional valence of experience, storytelling, and culture. Finally, new and emerging issues are raised for those interested in the study of narrative identity, with a particular focus on narratives that are difficult to tell and may violate cultural norms.     

Rapid acquisition of preference in concurrent chains: effects of d-amphetamine on sensitivity to reinforcement delay

The purpose of this study was to examine effects of d-amphetamine on choice controlled by reinforcement delay. Eight pigeons responded under a concurrent-chains procedure in which one terminal-link schedule was always fixed-interval 8 s, and the other terminal-link schedule changed from session to session between fixed-interval 4 s and fixed-interval 16 s according to a 31-step pseudorandom binary sequence. After sufficient exposure to these contingencies (at least once through the pseudorandom binary sequence), the pigeons acquired a preference for the shorter reinforcement delay within each session. Estimates of the sensitivity to reinforcement immediacy were similar to those obtained in previous studies. For all pigeons, at least one dose of d-amphetamine attenuated preference and, hence, decreased estimates of sensitivity to reinforcement immediacy; in most cases, this effect occurred without a change in overall response rates. In many cases, the reduced sensitivity to reinforcement delay produced by d-amphetamine resulted primarily from a decrease in the asymptotic level of preference achieved within the session; in some cases, d-amphetamine produced complete indifference. These findings suggest that a reduction in the sensitivity to reinforcement delay may be an important behavioral mechanism of the effects of psychomotor stimulants.     

Severity of unipolar depression and choice of treatment.

The National Institute of Mental Health (NIMH) Treatment of Depression Collaborative Research Program (Elkin et al., Archives of General Psychiatry, 46, 971-982; 1989) reported treatment-by-severity interactions favouring pharmacotherapy for more depressed outpatients, on a minority of relevant comparisons. The present study reports secondary analyses from a similar, preexisting data set in which treatment-by-severity interactions are systematically investigated with depressed outpatients treated either with nondirective psychotherapy, behaviour therapy, pharmacotherapy, or relaxation/placebo. Despite multiple severity measures and variable severity cut scores, no treatment was differentially effective in improving more severely depressed patients. Also, there was little difference across symptom severity levels in the proportions of recovered patients between treatment groups. Finally, dynamic cluster analysis demonstrated that the proportion of pharmacotherapy nonresponders (20%) did not differ from the proportion of nonresponders in behaviour therapy or placebo groups. It is concluded that this failure to replicate the NIMH trial findings can not be attributed to treatment differences, populations or statistical power. The suggestion that pharmacotherapy be the treatment of choice for more severely depressed outpatients appears to be unjustified on the basis of available evidence.     

Contrast and reallocation of extraneous reinforcers between multiple-schedule components

Four pigeons responded in components of multiple schedules in which two responses were available and reinforced with food. Pecks on the left key (“main” key) were reinforced at a constant rate in one component and at a rate that varied over conditions in the other component. When reinforcer rate was varied, behavioral contrast occurred in the constant component. On the right key (“extra” key), five variable-interval schedules and one variable-ratio schedule, presented conjointly, arranged reinforcers for responses in all conditions. These conjoint schedules were common to both multiple-schedule components—rather than unique to particular components—and reinforcers from these schedules could therefore be arranged in one component and obtained during the other component. In this way, the additional reinforcers were analogous to the “extraneous” reinforcers thought to maintain behavior other than pecking in conventional multiple schedules. Response rate on the extra key did not change systematically over conditions in the constant component, and in the varied component extra responding was inversely related to main-key reinforcement. All subjects obtained more extra-key reinforcers in whichever component arranged fewer main-key reinforcers. Consistent with the theory that reallocation of extraneous reinforcers may cause behavioral contrast, absolute reinforcer rate for the extra key in the constant component was low in conditions that produced positive contrast on the main key and high in those that produced negative contrast. Also consistent with this theory, behavioral contrast was reduced in two conditions that canceled extra-key reinforcers that had been arranged but not obtained at the end of components. Thus, a constraint on reallocation markedly reduced the extent of contrast.