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and how different forms of cognitive feedback may affect that adaptation.

Aging and Probabilistic Learning: Further Evidence.

G. Chasseigne François Rabelais University, France E-mail: chasseigne@univ-tours.fr

We have been pursuing the research program initiated in 1997, aimed at examining the effect of age on probabilistic learning. In a MCPL experiment, Chasseigne, Mullet and Stewart (1997) examined the ability of elderly people to learn inverse relationships between cues and criterion. Three age groups (20-30, 65-75, 76-90 years old) of participants were asked to learn to predict the value of a criterion on the basis of three cues. In a first condition all cue-criterion relationships were direct (positive linear). Elderly participants were able to learn nearly as well as young participants, whatever the performance measure considered. In a second condition two cue-criterion relationships were direct but the third was inverse (negative linear). In this condition, learning was significantly worse in the elderly than in the young participants. The lower performance of the elderly people as compared with the younger people was essentially due to their inability to learn the inverse relationship. The only thing they learned was not to use the cue with an inverse relationship with the criterion. In a third condition, subjects were given task information. The very elderly were not able to apply the knowledge of the inverse relationship provided by the cognitive feedback whereas the less elderly did not find it as difficult to modify their cognitive functioning. Chasseigne, Mullet and Stewart interpreted their result as a gradual decrease of cognitive flexibility in older adults.

In a recent study (Chasseigne et al., 2003), we examined further some of the conditions under which elderly people are able to learn probabilistic inverse relationships and when this type of learning is no longer possible. Two kind of tasks were used: (a) two single-cue learning tasks with either direct or inverse relationships (SCPL paradigm), and (b) three two-cue learning tasks, one with two direct relationships, one with a combination of direct and inverse relationships, and one with two inverse relationships (MCPL paradigm). Four groups of participants were included in the study: young adults (18-25 year-olds), adults (40-50 year-olds), elderly people (65-74 year-olds), and very elderly people (75-90 year-olds). It was shown that (a) older adults are able to reject the direct relationship “default” hypothesis and select the inverse relationship hypothesis when outcome feedback contradicting the default hypothesis is given, and provided that the

learning setting be a very simple one, involving only one cue; (b) some older adults are able to select the inverse relationship hypothesis provided that the learning setting be a simple one, involving only two inverse relationship cues; and (c) very few older adults are able to select the inverse relationship hypothesis when the learning setting is a complex one, involving two cues with both direct and inverse relationships with the criterion.

These results led to revise the “gradual decrease of cognitive flexibility in older adults” hypothesis proposed by Chasseigne, Mullet and Stewart. Moreover, there is a clear relationship between the Brunswikian probabilistic learning paradigms and the theoretical framework offered by the “executive function” construct. In the present study, the participants’ task was to learn inverse relationships. They had (a) to inhibit the prepotent DR response and to substitute an IR response, and (b) to plan a sequence of processes for correctly estimating a criterion value from two predictor values. Inhibiting was an easy task for all participants when the situation was reduced to a single-cue one. Planning a sequence of processes for estimating a criterion was also an easy task for all participants when the situation only involved DRs. However, (a) when the situation involved a higher level of executive functioning, that is, when the participants had to inhibit a prepotent response and coordinating two cue values of equal meaning (IR and IR), most elderly people failed, and (b) when the situation involved a still higher level of executive functioning, that is, when the participants had to inhibit a prepotent response and coordinating two cue values of opposite meaning (DR and IR), all elderly people failed.

Chasseigne, G., Ligneau, C., Grau, S., Le Gall, A., Roque, M., & Mullet, E. (2003). Aging and Probabilistic Learning in single- and multiple-cue tasks. Experimental Aging Research, 29 (in press). Chasseigne, G., Mullet, E., & Stewart, T. R. (1997). Aging and multiple cue probability learning : the case of inverse relationships. Acta Psychologica, 97, 235-252.

Decisions to Prescribe Antimicrobial Treatment

Petra Denig and Peter Mol Department of Clinical Pharmacology, University of Groningen, The Netherlands E-mail: p.denig@med.rug.nl

We are conducting a number of studies related to decisions to prescribe antimicrobial treatment, both in general practice and in hospital. Evaluations of actualprescribing showed that adherence to antimicrobial treatment guidelines is low for urinary

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