Switching attention between the ears to monitor tones Nigel Harvey

Alternating dichotic presentation of tones was compared with monaural presentation in two different perceptual tasks. When Ss were asked to detect higher frequency target tones in fists of six background tones, they missed less than 5%. However, when the presentation was fast (10/sec) and the tones alternated dichotically, Ss reported “hearing” only three or four tones. In two further experiments, Ss were asked to judge the number of tones or to report their spatial and temporal positions; these tasks were much less accurately performed, for the dichotic lists, than the target detection task. The differing effects of switching rate on these tasks are discussed in relation to the types of processing they require.     

Differential effects of repetition on pre- and postcategorical memory traces

The effect of list repetition on immediate recall for aurally presented nine-letter lists was studied under two conditions. In the first, a redundant stimulus item was presented as the tenth item in each list, while the suffix was not included in a control condition. As in previous research (Crowder & Morton, 1969), the stimulus suffix selectively interfered with recall at the terminal presentation serial positions, indicating the presence of precategorical acoustic storage. Repetition had a nonselective effect on performance. This result and an analysis of acoustic errors support the inference that qualitative differences in the memory code may lead to differences in other functional properties of the memory trace, such as responsiveness to repetition.     

Of mice and marbles: Novel perspectives on burying behavior as a screening test for psychiatric illness

Burying forms part of the normal behavioral routine of rodents, although its expression is species-specific. However, it has been suggested that aberrant burying behavior, of which marble-burying (MB) is an example, may represent neophobic and/or compulsive-like behavior. In the present investigation, we assessed MB in an established animal model of obsessive–compulsive disorder (OCD)—namely, spontaneous stereotypy in the deer mouse—to establish whether high (H) stereotypy is associated with neophobia and/or another compulsive endophenotype, i.e. MB, as compared to nonstereotypical (N) controls. A three-trial, one-zone MB test was performed over three consecutive evenings both before and after chronic treatment with high-dose (50 mg/kg/day) oral escitalopram. Neophobia was measured via the number of marbles buried during the first pre- and posttreatment MB trials, and compulsive-like behavior via the number of marbles buried over all pre- and posttreatment MB trials. The data from the present study support earlier findings that burying is a normal behavioral routine (inherent burying behavior, IBB) that is expressed by all deer mice, irrespective of stereotypical cohort, and is not associated with either neophobia or compulsiveness. Indeed, chronic escitalopram treatment, which is similarly effective in treating clinical anxiety and OCD, as well as in attenuating H behavior, failed to influence IBB. Although 11 % of the animals presented with a unique burying endophenotype (high burying behavior), escitalopram also failed to attenuate said behavior, necessitating further investigation as to its relevance. In conclusion, MB cannot be regarded as a measure of anxiety-like or compulsive behavior in the deer mouse model of OCD.     

Are absolute frequencies,relative frequencies,or both effective in reducing cognitive biases?

Biases in probabilistic reasoning are affected by alterations in the presentation of judgment tasks. In our experiments, students made likelihood judgments that an event was produced by various causes. These judgments were made in terms of probability, relative frequency or absolute frequency on a full or a pruned list of causes. When they had little personal experience of the event (causes of death), the pruning bias was smaller with relative frequencies than with absolute frequencies or probabilities. When they had more personal experience of the event (missing a lecture), the bias was less with both types of frequency than with probability but still lowest with relative frequency. We suggest that likelihood information is usually stored as relative frequencies when it has been obtained from public sources but that it is based on event counts when it is derived from personal experience. Copyright © 2000 John Wiley & Sons, Ltd.