Task switching in a hierarchical task structure: evidence for the fragility of the task repetition benefit

This study examined how task switching is affected by hierarchical task organization. Traditional task-switching studies, which use a constant temporal and spatial distance between each task element (defined as a stimulus requiring a response), promote a flat task structure. Using this approach, Experiment 1 revealed a large switch cost of 238 ms. In Experiments 2-5, adjacent task elements were grouped temporally and/or spatially (forming an ensemble) to create a hierarchical task organization. Results indicate that the effect of switching at the ensemble level dominated the effect of switching at the element level. Experiments 6 and 7, using an ensemble of 3 task elements, revealed that the element-level switch cost was virtually absent between ensembles but was large within an ensemble. The authors conclude that the element-level task repetition benefit is fragile and can be eliminated in a hierarchical task organization.     

The influence of irrelevant stimulus changes on stimulus and response repetition effects

In this study the influence of irrelevant stimulus changes from one trial to another in a serial reaction time task was investigated. Two experiments were performed in which subjects were required to respond to stimulus colour. Four colours were mapped on two response keys, so that colour and response repetition effects could be dissociated. In Experiment 1, the irrelevant stimulus dimension was location and in Experiment 2 it was shape. Both experiments were performed with a short and a long response-stimulus interval (RSI)-condition. In both experiments, the irrelevant dimension influenced the response repetition effect but not the colour repetition effect. In the reaction times, a response alternation effect was observed only when the irrelevant location of the stimulus changed in the long RSI-condition. The error rates showed a response alternation benefit for both irrelevant dimensions, in the short and the long RSI-condition. The benefit for response alternations is explained in terms of a response bias towards change that is triggered by a changing stimulus feature. We assume that the response bias is stronger for location than for colour and that accuracy is more sensitive to this bias than response latencies.     

The paradoxical effects of suppressing anxious thoughts during imminent threat

In line with the ironic processing theory of Wegner (Psychol. Rev. 101 (1994) 34), it is often argued that the suppression of anxiety-related thoughts results in a paradoxical increase of anxiety and thought intrusions, both after and during the thought suppression. In a sample of undergraduate students (14 men, 18 women), we investigated the effects of suppressing anxious thoughts about an imminent painful electrocutaneous stimulus. During thought suppression, self-reported anxiety and frequency of anxious thoughts did not increase, and duration of anxious thoughts decreased. After thought suppression, participants experienced an increase in self-reported anxiety and the frequency of anxious thoughts. There was no effect upon thought duration. The results support the idea that suppression of anxiety-related thoughts may result in a paradoxical increase in anxiety, and may cause and/or maintain anxiety problems.     

An experimental test of the effect of weight-loss dieting on bulimic pathology: tipping the scales in a different direction

Although it is widely accepted that dieting increases the risk for bulimic pathology, this hypothesis has not been tested in a randomized experiment. Accordingly, the authors conducted an experimental test of the dietary restraint model by randomly assigning nonobese women (N = 82) to either a 6-week, low-calorie diet or a waitlist control condition. The diet intervention resulted in significant weight loss, confirming that dieting was successfully manipulated. Contrary to the restraint model, dieting resulted in significant decreases in bulimic symptoms relative to the control condition. Results converge with past findings from randomized obesity prevention and treatment trials and provide evidence that dieting does not promote bulimic pathology; rather, effective decreases in caloric intake appear to reduce bulimic symptoms.     

Do people still report dreaming in black and white? An attempt to replicate a questionnaire from 1942

In the 1940s and 1950s many people in the United States appear to have thought they dreamed in black and white. For example, Middleton (1942) found that 70.7% of 277 college sophomores reported "rarely" or "never" seeing colors in their dreams. The present study replicated Middleton's questionnaire and found that a sample of 124 students in 2001 reported a significantly greater rate of colored dreaming than the earlier sample, with only 17.7% saying that they "rarely" or "never" see colors in their dreams. Assuming that dreams themselves have not changed over this time period, it appears that one or the other (or both) groups of respondents must be profoundly mistaken about a basic feature of their dream experiences.     

Inferring the mental processes of other minds

In 4 experiments, the authors examined how several variables influence the quality and quantity of information that people use to make judgments about other people. The results showed that when possible, participants consistently responded appropriately to variables that influenced information that they used to make inferences about other minds. The results also suggested that under circumstances with no opportunity to contrast behavior in different situations, people might not be sensitive to the quality and quantity of information present. The authors interpreted results to mean that under most circumstances, people make inferences in a way that efficiently uses information about the causes of behavior.     

The nature of speech production impairments in anterior aphasics: an acoustic analysis of voicing in fricative consonants

This study investigated the acoustic characteristics of voicing in English fricative consonants produced by anterior aphasics and the effects of phonetic context on these characteristics. Three patients produced voiced and voiceless fricative-vowel syllables in isolation, following a voiced velar stop, and following a voiceless velar stop. Acoustic analyses were conducted of the amplitude and patterning of glottal excitation, as well as fricative noise duration. Results showed that, although the patients are able to coordinate the articulatory gestures for voicing in fricative consonants, they demonstrated abnormal patterns of glottal excitation in the amplitude measures, owing to weaker amplitudes of glottal excitation in voiced fricatives. Context effects failed to emerge because of dysfluent speech. These results suggest that the locus of the speech production deficit of anterior aphasics is not at the higher stages of phoneme selection or planning but rather in articulatory implementation, one related to laryngeal control.     

The excluded player in coalition formation

Coalition research generally assumes that people strive to maximize their share of the coalition payoff and that they exclude others from joining a coalition if these others are not needed to obtain the coalition payoff. In two experiments, the authors show that this view is too narrow and that willingness to include such others is dependent on the extent to which people feel that exclusion affects the payoff of the excluded player. This finding was moderated by social value orientations. Proselfs were not affected by the consequences for the excluded players. Prosocials were less willing to exclude others the more harmful were the consequences of exclusion. Results are related to research on social exclusion, the do-no-harm principle, and social value orientations.     

Individual differences in the responses of naïve rhesus monkeys to snakes

The authors demonstrated individual differences in inhibited behavior and withdrawal responses of laboratory-born rhesus monkeys when initially exposed to a snake. Most monkeys displayed a small significant increase in their behavioral inhibition in the presence of a snake. A few monkeys had marked responses, and some actively withdrew. Although the responses of the most extreme laboratory-born monkeys were comparable to feral-born monkeys, the responses of the laboratory-born monkeys rapidly habituated. The individual differences in the responses of na?ve monkeys likely reflect a continuum from orienting to wariness to fear. A neurobiological model is presented that addresses potential mechanisms underlying these individual differences, their relation to fear, and how they may predispose to phobia development.