Optimal predictions in everyday cognition

Human perception and memory are often explained as optimal statistical inferences that are informed by accurate prior probabilities. In contrast, cognitive judgments are usually viewed as following error-prone heuristics that are insensitive to priors. We examined the optimality of human cognition in a more realistic context than typical laboratory studies, asking people to make predictions about the duration or extent of everyday phenomena such as human life spans and the box-office take of movies. Our results suggest that everyday cognitive judgments follow the same optimal statistical principles as perception and memory, and reveal a close correspondence between people's implicit probabilistic models and the statistics of the world.     

Effects of a cognitive-behavioural internet program on depression, vulnerability to depression and stigma in adolescent males: a school-based controlled trial

This study evaluated the effectiveness of a cognitive behaviour therapy Internet program (MoodGYM) for depressive symptoms, attributional style, self-esteem and beliefs about depression, and on depression and depression-vulnerable status in male youth. A total of 78 boys age 15 and 16 years were allocated to either undertake MoodGYM or to standard personal development activities. Outcomes were measured before commencement, post-program and 16 weeks post-program. There were no significant between-group differences in change scores pre- to post- or pre- to follow-up using the intention to treat sample or for participants with post- and/or follow-up data. For boys completing 3 or more modules there were small relative benefits of MoodGYM for depressive symptoms (Effect Size, ES = 0.34), attributional style (ES = 0.17) and self-esteem (ES = 0.16) at post-program, although only the effect for self-esteem was sustained at follow-up. Both groups showed improvement in their beliefs about depression at follow-up, with the control group showing a moderate relative benefit (ES = 0.40). While the numbers are small, there was a reduction in the risk of being depressed in the MoodGYM group of 9% at post-treatment compared with a slightly increased risk for the control group. The risk of being classified as vulnerable to depression reduced by 17% in the MoodGYM group at post-treatment compared with no change in risk for the control group. These reductions in risk for the MoodGYM group were not sustained at follow-up. The limitations of the study highlight several important challenges for MoodGYM and other self-directed Internet cognitive behaviour therapy programs. These include how to ensure enough of the program is received and that people who could potentially benefit access the program and continue to remain engaged with it, and how to enhance the sustainability of any benefits.     

Theory-based Bayesian models of inductive learning and reasoning

Inductive inference allows humans to make powerful generalizations from sparse data when learning about word meanings, unobserved properties, causal relationships, and many other aspects of the world. Traditional accounts of induction emphasize either the power of statistical learning, or the importance of strong constraints from structured domain knowledge, intuitive theories or schemas. We argue that both components are necessary to explain the nature, use and acquisition of human knowledge, and we introduce a theory-based Bayesian framework for modeling inductive learning and reasoning as statistical inferences over structured knowledge representations.     

Speech-specific auditory processing: where is it?

Are speech-specific processes localized in dedicated cortical regions or do they emerge from developmental plasticity in the connections among non-dedicated regions? Here we claim that all the brain regions activated by the processing of auditory speech can be re-classified according to whether they respond to non-verbal environmental sounds, pitch changes, unfamiliar melodies, or conceptual processes. We therefore argue that speech-specific processing emerges from differential demands on auditory and conceptual processes that are shared by speech and non-speech stimuli. This has implications for domain- vs. process-specific cognitive models, and for the relative importance of segregation and integration in functional anatomy.     

Reinforcing effects of caffeine in coffee and capsules.

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "linking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.     

Repeated diazepam administration: effects on the acquisition and performance of response chains in humans.

The effects of repeated diazepam administration (80 mg) were assessed across a 12-hr time course with humans responding under a two-component multiple schedule of repeated acquisition and performance of response sequences. Subjects resided in an inpatient clinical research ward for the duration of the study. In each component of the multiple schedule, subjects completed sequences of 10 responses in a predetermined order using three keys of a numeric keypad. In the acquisition component, a new response sequence was to be acquired each session. In the performance component, the response sequence always remained the same. After stable responding was obtained and the effects of the placebo assessed, diazepam was administered for 3 consecutive days. The effects of repeated diazepam administration on overall percentage of errors across the two components of the multiple schedule were selective. In the acquisition component, the first dose of diazepam increased percentage errors with the magnitude of effects decreasing across the second and third days of diazepam administration. In the performance component, the percentage of errors was either minimally affected across all 3 days of diazepam administration or substantively increased on Day 1 with subsequent diazepam administrations having minimal effects. Effects on response rate were not selective. Diazepam decreased rates of responding in both schedule components, with the magnitude of effects decreasing across successive administrations. These results replicate previous findings in humans and nonhumans on the selective effects of diazepam on acquisition versus performance baselines. Also, the results suggest that the selective effects do not result from differences in reinforcement rate. Finally, the present results demonstrate that the selective recovery from repeated drug administration previously demonstrated in nonhumans using a repeated acquisition arrangement has generality to human behavior.     

Computer game playing in adolescence: Prevalence and demographic indicators

Computer game playing is a popular activity among adolescents yet there have been no systematic studies in the U.K. on its prevalence and its demographics. A questionnaire study was undertaken with 387 adolescents (12–16 years of age) to establish the time spent playing computer games, who they first started playing with, the reasons why they first started and why they play now and negative consequences of play. Results revealed that for many adolescents, home computer game playing can take up considerable time with 7% of the sample playing for at least 30 hours a week. Although there were no differences between males and females in who played computer games, it was established that males were found to play significantly more regularly than females.     

A procedure for studying the within-session onset of human drug discrimination.

The purpose of the present study was to develop a procedure for measuring the within-session onset of human drug discrimination. During daily sessions, under double-blind conditions, caffeine-abstinent adults ingested a letter-coded capsule containing 178 mg caffeine or placebo. Trials were presented at 30-s intervals, beginning immediately after drug ingestion and continuing for 60 min. On each trial, subjects could guess which of their two letter-coded drugs they had received by pressing a left button (for one drug) or right button (for the other drug); subjects could also press a center "no guess" button instead of guessing. Each trial ended after one button press. After each session, subjects were told which drug they had received. Subjects earned one point (worth $0.10 per point) for each correct guess. Subjects lost either 0, 1, or 10 points for each incorrect guess; the point-loss contingencies were varied in random order across sessions. Discrimination earnings accumulated across all sessions. The point-loss contingencies decreased random responding and delayed the discrimination time course. Overall, this procedure provided an orderly and relatively continuous measure of the within-session onset of drug discrimination and should have a range of applications in understanding the human behavioral pharmacology of drugs.     

Breaking the bad news: dilemmas in shared decision-making in medical practice

In a review of the literature, very little empirically based research was uncovered to guide the practice of health professionals who need to tell their patients bad news and help them to decide on their preferred treatment option. Various practising styles and guidelines are presented, and ethical and crosscultural challenges discussed. An enormous amount of research still needs to be done to discover the least stressful ways of dealing with these issues in health care settings.     

Representation of spatial structure in reaching to a visual target.

Reaches made without feedback to positions on an object's surface reflect the spatial form of the surface. In Experiment 1, the reaching pattern varied with the stimulus surface's spatial attributes, consistent with a point-by-point perceptual representation of the surface. In Experiment 2, systematic reaching errors were determined solely by target position regardless of surface structure, implying a highly consistent representation of location. In Experiment 3, illusory slant was imparted to a surface by an aniseikonic lens. Individual variations in directly judged slant were reflected in the reaching pattern, implying organization of local perceptual representation of location and global perception of spatial attributes of the stimulus into a coherent structure.