Andrew J. Tilley

The impact of night work on psychological well-being

This study tested the efficacy of selected personality, behavioural, and social/organizational variables as predictors of adaptation to night work. Sixty female student nurses were studied during their first 15 months of shiftwork. Twenty-two worked on rotating day and afternoon shifts throughout, while the remaining 38 began regular night shifts after six months. Psychological symptoms were measured at baseline (Stage 1), six months (Stage 2) and 15 months (Stage 3). Repeated measures analysis of variance revealed a significant shift group x symptoms interaction (p less than 0.05) between Stages 2 and 3. Only the night workers displayed a significant increase (Tukey HSD: p less than 0.01) in symptoms between Stages 1 and 3. Multiple regression analysis revealed that neuroticism and perceived work/nonwork conflict predicted symptoms at Stage 2. Night work, social support from supervisors, and morningness were predictors at Stage 3. These results suggest that organisational, behavioural, and physiological factors moderate the impact of night work on psychological well-being, and personality factors do not.

Transcultural Properties of the Composite Scale of Morningness: The Relevance of the “Morning Affect” Factor

Morningness scales have been translated into several languages, but a lack of normative data and methodological differences make cross‐cultural comparisons difficult. This study examines the psychometric properties and factor structure of the Composite Scale of Morningness (CSM) in samples from five countries: France (n=627), Italy (n=702), Spain (n=391), Thailand (n=503), and Australia (n=654). Strong national differences are identified. A quadratic relationship between age and CSM total score was apparent in the Australian data with a downward trend after age 35 yrs. There was no age effect in any sample in the range from 18 to 29 yrs. Factor analysis identified a three‐factor solution in all groups for both men and women. Tuckers congruence coefficients indicate that: (1) this solution is highly congruent between sexes in each culture, and (2) a morning affect factor is highly congruent between cultures. These results indicate there are national differences in factorial structure and that cut‐off scores used to categorize participants as morning‐ and evening‐types should be established for different cultural and age groups.

Psychometric evaluation of the early/late preferences scale.

This paper examines the psychometric quality of the Early/Late Preferences Scale (PS) relative to that of the Composite Morningness Scale (CS). Questionnaires were completed by 670 undergraduate students aged 16–37 years (mean 22.5), of whom 64% were female. Both scales displayed satisfactory inter-item correlations and similar total mean scores to those reported previously, although the CS had higher variability. Principal axis factor analysis produced single-factor solutions for both scales, although loadings for Items 7 and 9 on the PS were low. Internal consistencies for both scales were good (PS = 0.86, CS = 0.90) with only a small improvement achieved by deleting Items 7 and 9 from the PS. Test-retest reliability over 11 weeks was good for both scales (PS = 0.92, CS = 0.89). Differences between morning, evening and intermediate groups in self-rated alertness at different times of day, and significant correlations with other indices of morning-evening orientation, provided evidence of validity for both scales. These results indicate that PS is psychometrically comparable with CS. In view of its simpler format and lower cultural specificity, PS may be considered a preferable measure for most applications.

Predicting mood change on night shift

This study examined the impact of night shift on six dimensions of mood. The efficacy of a range of personality, behavioural, and social/organizational predictors of these responses was also examined. Thirty-five female student nurses were studied during their first period of night work. ANOVAs indicated that only fatigue-inertia and vigour-activity were significantly affected by night work. Multivariate profile analyses revealed that significant changes were predominantly confined to the interval between the preceding rest day (B) and the first night (N1), although vigour-activity dropped significantly between N1 and N2 and rose significantly by N5 for one group of subjects. Multiple regression analyses revealed that morningness, neuroticism, work-non-work conflict, and sleep quality between shifts predicted fatigue-inertia. Extroversion and social support from both co-workers and family predicted vigour-activity. Extroversion and social support from co-workers appeared to predict the positive affect component of vigour-activity, rather than the vigour and energy component.

Evaluating two morningness scales with item response theory

Using a student sample (n=692) and an organization sample (n=180), we scrutinized two morning–evening orientation scales using item response theory (IRT) methods. We used IRT to compare the measurement precision of the Composite Scale (CS) and the Early/Late Preferences Scale (PS). The CS had slightly higher measurement precision at all ranges of orientations, except for extreme morning and evening orientations for which the PS had slightly higher precision. IRT item-level statistics were also computed to try to understand how morning-orientation items functioned. Items that asked questions about morning activities tended to be more discriminating indicators of morning-orientation than items that asked about evening or peak performance activities. Items that involved unpleasant activities were less frequently endorsed than items that involved neutral or enjoyable activities. Implications for measurement of morning–evening orientation are discussed.

The changing face of perceptual rivalry

Functional brain-imaging studies of house-face binocular rivalry and Rubins vase-faces illusion have consistently reported face perception-dependent activity in the right fusiform gyrus. Here we use Rubins illusion and report that activation of the left hemisphere by caloric vestibular stimulation increases the predominance of the faces percept in a substantial number of test subjects. While partially supporting the brain-imaging lateralization reports, our findings also challenge these studies by suggesting that neural mechanisms of Rubins illusion cannot be limited to extrastriate perception-dependent processing. In accordance with our previously proposed interhemispheric switch model, the present findings support the notion that perceptual rivalry engages high-level cortical structures that mediate unihemispheric attentional selection.

The relationship between diurnal type and time duration estimation at morning and evening times of day

This study investigates whether different diurnal types (morning versus evening) differ in their estimation of time duration at different times of the day. Given that the performance of morning and evening types is typically best at their preferred times of day, and assuming different diurnal trends in subjective alertness (arousal?) for morning and evening types, and adopting the attentional gate model of time duration estimation, it was predicted that morning types would tend to underestimate and be more accurate in the morning compared to evening types where the opposite pattern was expected. Nineteen morning types, 18 evening types and 18 intermediate types were drawn from a large sample (N=1175) of undergraduates administered the Early/Late Preference Scale. Groups performed a time duration estimation task using the production method for estimating 20-s unfilled intervals at two times of day: 0800/1830. The median absolute error, median directional error and frequency of under- and overestimation were analysed using repeated-measures ANOVA. While all differences were statistically non-significant, the following trends were observed: morning types performed better than evening types; participants overestimated in the morning and underestimated in the evening; and participants were more accurate later in the day. It was concluded that the trends are inconsistent with a relationship between subjective alertness and time duration estimation but consistent with a possible relationship between time duration estimation and diurnal body temperature fluctuations

Twisting the Night Away: The Effects of All Night Disco Dancing on Reaction Time

8 subjects performed an unprepared simple reaction time task for 20 min. every 2 hr. while taking part in an all night disco dancing marathon (continuous exercise) and during a control (no exercise) night. Mean reaction times were significantly faster and less variable during the dance marathon. It was suggested that the effects of continuous exercise in the form of disco dancing may be to reduce drowsiness which in turn assists performance.

The effect of prior sleep on retrieval

Sleeping immediately prior to learning impaires subsequent retention. The purpose of this study was to ascertain if relatively short-term (0 to 20 mins) retention deficits are the result of impaired retrieval at the time of testing. 24 young women students were randomly allocated to two groups: prior sleep and awake. The prior sleep group was required to generate (retrieve) instances of specified categories immediately upon awakening from the first hour or so of nocturnal sleep and repeated the task again after a delay of 20 minutes. The awake control group performed the task at exactly the same times of night but without having had any prior sleep. The prior sleep group retrieved significantly fewer category instances immediately upon awakening and at delayed testing. However, retrieval had significantly improved during the 20 mins delay. It was concluded that the detrimental effects of prior sleep on retention over relatively short intervals may in part be due to retrieval difficulties at the time of testing but that longer-term retention deficits (less than 20 mins) are more likely to be due to impaired memory consolidation.

DREAM THEMES: EFFECT OF A SERIES OF THEMATICALLY RELATED WORDS ON THE CONTENT OF DREAMS

Dreams can be influenced by external stimuli. In this study attempts were made to influence or direct the theme of a dream or sleep mentation using a series of thematically related words. 10 subjects were presented one of four series of 6 tape-recorded theme words, repeated 10 times, during REM or Stage 2 sleep followed by awakening to collect the dream or mentation report. Of the 40 awakenings, 30 produced a report, 10 of which were judged by two “blind” judges to be on the same or a very similar theme to the words. It was concluded that the theme of a dream can be influenced by the theme of the words.