Differential study of fluctuations in performance of a complex task during the course of a day

Author(s): Lancry, A.

Journal/Book: Trav Hum. 1998; 61: Service Des Periodiques, 12 Rue Jean de Beauvais, 75005 Paris, France. Univ France. 153-169.

Abstract: The LER (Reactivity Evaluation Programme) that allowed us to confront our subjects with a complex task requiring many cognitive functions and therefore both going beyond the modular approach of cognition and improving the ecological validity of experimental! results (this tool was developed in nuclear power stations, by analysis of operators activity). In order to determine our variables, we divided people into morning and evening types based an their own subjective ratings and made two groups of subjects whose performances on the programme (speed and quality) were measured at different times of the day. We could thus follow the evolution of indicators respectivly reflecting vigilance, memory, spatial representation, and problem solving. Our study has shown that cognitive function are not equally efficient at all limes of the days. Several different indices were recorded, both with emphasis on speed and on quality. Moreover, taking into account the typology?, of subjects the results can be extended to apply to a typical cross-section of the population. The results concerning reaction times are in accordance with previous observations by Horne, Brass, & Pettitt (1980) and Patkai (1971) : early risers work faster in the mornings. On the other hand, our experiment shows reaction times to be constant during the course of a day for evening subjects. Whilst both early risers and evening subjects detect an equal number of incidents in the morning, the latter take the lead in the afternoon. In addition, the percentage of pans nor checked increases for early risers during the course of the day, showing a decrease in work memory quality. Evening subjects, on the other hand, show stability. These results are similar to those cited by Folkard, Monk, & Knauth (1976, 1980) further confirming the importance of taking into account differences between individuals. These writers, who did nor use the morning/evening distinction in their research, noted a continuous decrease in efficiency of short term memory during the course of the day. Our results are similar close to those described by Lancry (1986), who found significant differences between morning and evening subjects at 16 h 00 and 20 h 00: here the difference lies in the significance of 10 h 15. Unlike Lancry (1986), however, zee did nor record any fluctuations in long term memory performance either within each of the two groups, or between them. Problem resolution quality (automatic evaluation of success) is constant throughout the course of the day for evening subjects, and diminishes for early risers. This results giver added precision to the conclusions of Folkard (1975), who conducted a test of syllogistic reasoning and observed that quality was better in the morning than in the evening.

Note: Article Lammens JM, Univ Picardie, Fac Philosophie Sci Humaines & Sociales, Campus Univ, Chemin Thil, F-80025 Amiens 01, FRANCE

Keyword(s): complex task; morning types; evening types; fluctuations; performance; CIRCADIAN-RHYTHMS; MEMORY

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