Psychology Report

Psychology Report

Abstract

Morningness-Eveningness refers to individual differences in circadian phase position of spontaneous sleep-wake rhythms and to subject alertness. There is some evidence indicating that performance on cognitive tasks may be influenced by Morningness-Eveningness and time-of-day. Given the potential importance of such a finding for the assessment of cognitive ability we conducted a study assessing the relationship between Morningness-Eveningness, time-of-day.Introduction

Morningness-Eveningness (M-E) refers to individual differences in circadian phase position of spontaneous sleep-wake rhythms and to subjective alertness. Individuals can be classified as either Morning Types (MTs), Evening Types (ETs) or the intermediate type-Neither Types (NTs) with the latter being the most common classification (Lacoste & Wetterberg, 1993). Hur, Bouchard and Lykken (1998) have reported that 50% of the variability in M-E is attributable to genetic variance.

MTs rise earlier in the day, retire earlier at night and show less variable sleep duration compared to ETs. Consistent with these distinctions is the observation that oral temperatures of MTs generally peak 2 h earlier than that of ETs (Lacoste & Wetterberg, 1993). In addition, MTs also begin the day with higher body temperature and record a steeper rise in temperature in the morning relative to that of ETs. Conversely, the temperature of ETs rises steadily during the day and peaks in the middle evening. After reaching their respective peaks, the rates of decline of body temperature for MTs and ETs are the same (Horne, Brass & Pettitt, 1980).

The categorization of M-E types is typically achieved from self-report questionnaires. The most commonly used questionnaire for assessing M-E is the Horne and Östberg (1976) Morningness-Eveningness Questionnaire (MEQ) which has been translated into Italian, Spanish and Japanese, and successfully validated against a range of physiological responses (Ishihara, Saitoh, Inoue & Miyata, 1984).

Physiological measures such as adrenaline excretion (Patkai, 1971), skin conductance (Wilson, 1990) and salivary cortisol levels (Bailey & Heitkemper, 1991) have been shown to differentiate MTs and ETs. MTs excrete more adrenaline and display larger auditory and visual evoked potentials in the morning than in the evening whilst ETs show an opposite tendency (Kerkhof, Korving, Willemse, Geest & Rietvald, 1980).

M-E types also differ on psychological processes (Costa, Lievore, Casaletti & Gaffuri, 1989), and circadian rhythmicity has been found to be more successful in discriminating individuals than personality traits (Tankova, Adan, & Buela-Casal, 1994). Nonetheless, Eveningness has been reported to correlate with extraversion, specifically sociability in some (Wilson and Neubauer) but not in all studies (Matthews, 1987).

In a study using a simulated production-line inspection task, MTs performed better than ETs in the morning while ETs performed better than MTs in the evening (Horne et al., 1980). When performances in the morning, early afternoon, and evening were compared, Horne et al. reported that the greatest differences in performance between M-E types occurred in the morning while least differences were found during early afternoon.

Aim of the study

The relationship between M-E, time-of-day and intellectual performance is the focus of the present research. It is hypothesised that performance on the cognitive tasks (MAB and IT) will vary at ...