and evening types, meaning by morning types those Ss whose body temperature ... In this way, the variable time of application is formed by four situations:.
Person. indid. 018 Vol. I I, No. 5. pp.447450. Printed in Great Britain. All rights reserved
DIFFERENCES
1990 Copyright
0191-8869190 $3.00 + 0.00 % 1990 Pcrgamon Press plc
BETWEEN MORNING AND EVENING TYPES IN PERFORMANCE
G. BLJELA CASAL,‘* V. E. CABALLO’
and E. GARcfA CUETO*
’ Department of Personality, Assessment and Psychological Treatment, Colegio Universitario de JaCn, 23071 Jaen and *Department
of Methodology of Behavioral Sciences, Universidad Complutense Madrid, Somosaguas, Madrid, Spain (Received
de
30 June 1989)
Summary-In this study, the differences in the activity rhythm of morning and evening types of university students were examined. The subjects were administered various tasks, including performance, concentration, and reaction time tasks; the level of self-reported activity was assessed. The tasks were applied first thing in the morning or very late in the evening. Significant differences were found in the reaction time and the level of self-reported activity.
Independent of external stimulation, the level of arousal is subject to variations regulated by a biological rhythm. Based upon extreme scores in this variance the Ss can be classified into morning and evening types, meaning by morning types those Ss whose body temperature reaches its maximum level early in the afternoon (Passouant, 1976). They experience quick sleepiness and it is also characteristic of these Ss that they reach a deep sleep before the other Ss. The deep sleep decreases gradually until the moment they awake, getting up feeling alert and awake. The evening types, however, show opposite characteristics to the former Ss. In the evening types the curve of the body temperature does not reach its maximum value until late in the evening and in some cases, late at night. The evening types take longer to fall asleep, even though they tend to go to sleep later than the morning types. In the polysomnographic recordings, one may observe how phase IV appears much later, presenting itself in some cases at the end of the night (Buela Casal, 1984). Horne, Brass and Pettitt (1980) carried out a study about morning and evening types, in which they used a self-report questionnaire in order to classify the Ss as morning or evening types. They were later given the task of disregarding the irrelevant elements in a transport tape. The morning types had the highest accuracy at 8 a.m. and the lowest at 8 p.m., whereas the evening types showed exactly the opposite. In light of what has been previously discussed, it seems logical to think that morning types would show the maximum level of arousal first thing in the morning, and the minimum level late in the evening, whereas the evening types would reach a minimum level first thing in the morning and a maximum level late in the evening. In order to prove what is mentioned above, we designed the present study in which we analyzed the relation between different measures of perfomance, reaction time and level of self-reported arousal, in morning and evening types.
METHOD
Subjects
The selected Ss included 33 university students (29 women, 4 men) ranging between the ages of 19-23. These Ss were chosen from a sample of 300 students, and in light of their self reports regarding the arousal rhythm, 13 Ss were classified as early risers (level of arousal highest early in the morning) while the other 20 Ss were classified as nightwatchers (level of arousal highest late in the morning). *To whom all correspondence
should he addressed. 447
448
Variables
G. BCELA CASAL er
al.
and instruments
The variables and instruments used were as follows: reaction time (RT) in perceptual motor tasks (measured with a program in ‘basic’ language and a microcomputer PC), ability to concentrate and resistance to fatigue [measured with the Tolouse Pieron Test (TP)]. In the same way, we assessed the self-perceived level of arousal at the moment of the application of the tests used in the Stanford Sleepiness Scale (SSS) (Hoddes, Dement & Zarcone, 1972; Hoddes, Zarcone, Smythe, Phillips & Dement, 1973) the ability to maintain static visualization [measured with the Solid Figures Rotation Test (FRT)], calculating speed (measured with a test which consists in identifying correct and incorrect additions) and memory (measured by checklists). Procedure
In light of the endogenous variation in the rhythm of arousal, we selected those Ss who showed extreme scores on a scale in which they had to identify their rhythm of arousal; that is to say, those Ss who had a higher level of arousal first thing in the morning or at the end of the day. In order to measure the validity of the self-perception, we assessed several parameters which we considered valid indices of arousal level. This was executed with the purpose of examining whether there is a relationship between these scores and the arousal rhythm. We applied a counterbalanced method so that half of the nightwatcher Ss and half of the earlyrisers were given the test first thing in the morning; whereas the rest of the Ss were given the test late in the evening. In this way, the variable time of application is formed by four situations: earlyrisers tested in the morning (EM), nightwatchers tested in the morning (NM), earlyrisers tested in the evening (EE) and nightwatchers tested in the evening (NE). RESULTS The data were analyzed by means of the BMDP statistical software, using the following techniques: factorial analysis (BMDP 4M), cross tabulation (BMDP 4F) and analysis of variance (BMDP 3s). In order to measure the inter-test consistency, factor analysis was carried out, following the method of maximum certainty for the rotation and factor extraction. Two factors were obtained, which explain 57% of the variance. In the first factor the following measures loaded: RT, memory, TP, and calculating speed; with the other variables loading below 0.5. In the second factor, only the SSS and the capacity for visualization loaded above 0.5 (see Table 1). In order to analyze if the scores in each variable were related to the time of application a cross tabulation was carried out. Two variables were related to the time of application, the RT (P -C 0.01) and SSS (P < 0.05); the TP presented a high, though not significant, tendency (P = 0.075) (see Table 2). Table I. Factor analvsis of the variables used Correlation matrix
sss
sss(1) FRT (2) Memory (3) Calculations (4) -fP (5) RT (6)
(1) l.om -0.242 -0.034 0.174 -0.047 0.157
FRT (2) l.OQO 0.136 0.001 0.216 -0.099
Memory (3)
Calculations (4)
l.OOil 0.238 0.342 -0.541
0.268 -0.170
TP (5)
RT (6)
I.000 -0.505
I.000
I.000
Sorted rotated factor loadings (pattern)’
R-f (6) Memory (3) TP (5) Calculations sss (II FRT (2)
Factor I - 0.794 0.757 0.755 0.531 0.000 0.000
Factor 2 0.000 0.000 0.000 0.000 0.813 -0.629
‘The above factor loading matrix has been rearranged so that the columns appear in decreasing order of variance explained by factors. The rows have been rearranged so that for each successivefactor, loadings >0.5 appear first. Loadings ~0.5 have been replaced by zero.
Differences Table 2. Multiway Application time
-25
25-50
SO-75
Percents of the total table (SSS) EM 12.1 6.1 NM EE NE
?Sf
in performance
frequency
24.2
51.5
21.2
3.0
100.0
3.0 9.1 6.1 6.1
9.1 3.0 3.0 9.1
18.2 33.3 21.2 27.3
24.2
24.2
100.0
9.1 9.1 3.0 3.0
3.0 3.0 9.1 12.1
18.2 33.3 21.2 21.3
24.2
27.3
100.0
3.0 9.1 6.1 3.0
9.1 3.0 3.0 9.1
18.2 33.3 21.2 21.3
21.3
21.2
24.2
100.0
Percents of the total table (TP) EM 3.0 3.0 NM 12.1 18.2 EE 6.1 0.0 NE 3.0 6.1
6.1 3.0 9.1 3.0
6.1 0.0 6. I 15.2
18.2 33.3 21.2 21.3
18.2
Total
21.2
27.3
Percents of the total table (calculations) EM 3.0 3.0 NM 9.1 12.1 EE 6. I 6.1 NE 9.1 6.1 Total
Total
21.3
24.2
21.3
21.2
27.3
100.0
Percents of the total table (RT) EM 3.0 9.1 NM 3.0 0.0 EE 12.1 0.0 NE 6.1 18.2
3.0 15.2 3.0 3.0
3.0 15.2 6. I 0.0
18.2 33.3 21.2 21.3
Total
24.2
24.2
100.0
24.2
21.3
0.033
PEARS. CHIS. 0 CONT. COEF.
IO.126 0.554 0.485
9
0.340
PEARS. CHIS. f#J CONT. COEF.
10.778 0.571 0.496
9
0.29 I
PEARS. CHIS. ql CONT. COEF.
5. I80 0.396 0.368
9
0.818
PEARS. CHIS. $J CONT. COEF.
15.625 0.688 0.567
9
0.075
PEARS. CHIS. 4 CONT. COEF.
23.021 0.835 0.641
9
0.006
&NT.
Percents of the total table (FRT) EM 6.1 0.0 NM 18.2 3.0 EE 3.0 9.1 NE 6.1 6.1 33.3
9
COEF.
18.125 0.741 0.59 I
PEARS.
21.2 33.3 27.3
Percents of the total table (memory) EM 3.0 3.0 NM 12.1 9.1 EE 6. I 3.0 NE 0.0 12.1
d.f.
18.2
0.0 3.0 0.0
Total
Value
0.0
IS.2 6.1 0.0
models)
Statistic
0.0
15.2 9.1 21.2
Total
tables (loglinear
Total
0.0 6.1 6.1
449
CHIS.
Probability
In order to see whether there were differences in the test performances, according to the four situations of application (EM, NM, EE, NE), a Kruskal-Wallis Test was applied, using as the group criterion whether or not the Ss belonged to each application situation. The results show significant statistical differences (P < 0.05) in RT and SSS. Similarly to the above technique, the TP was almost significant, reaching P = 0.058 (see Table 3).
DISCUSSION From the results of this study, we can conclude that there exists a notable difference between the arousal rhythm in morning and evening types, and that this rhythm significantly affects simple reaction time and concentration level, whereas other types of tasks, such as memory, calculating speed and spatial perception are not affected. In respect to self-perceived level of arousal, the Table 3. Kruskal-Wallis Variable sss FRT Memory hh,kdtiOnS
TP RT
lP < 0.05.
Kruskal-Wallis II.13 4.00 4.20 0.55 1.48 10.27
analysis Significance 0.0111’ 0.2614 0.241 I 0.9087 0.0582 0.0164*
450
G. BUELACASAL Edal.
Ss showed that they were able to identify their level of arousal with similar accuracy to the reaction time. This relationship between reaction time and self-perceived arousal level is also apparent in Glenville and Broughton’s results (1979). Therefore, the Ss self-perception of their arousal rhythm is considerably accurate; this fact is clearly shown when the arousal rhythm is assessed by the RT and the SSS. The TP also showed significant fluctuations in relation to time of application, even though it was not statistically significant. These variables may be considered as small measures of arousal rhythm, because one must remember that in this study, the Ss were healthy adults in a normal situation, with their arousal rhythm being their only difference. REFERENCES Buela Casal, G. (1984). Aspectos psicologicos del suetio: patrones hipnologicos humanos. Tesis de Licenciatura. Universidad de Santiago de Compostela. Glenville, M. & Broughton, R. (1979). Reliability of the Stanford Sleepiness Scale compared to the short duration performance tests and the Wilkinson auditory vigilance task. In Passouant, P. & Oswald, I. (Eds), Pharmacology of the states of alertness. Oxford: Pergamon Press. Hoddes, E., Dement, W. C. & Zarcone, V. (1972). The history and use of the Stanford Sleepiness Scale. Psychophysiology (Absrr.), 9, 150. Hoddes, E.. Zarcone, V., Smythe, H., Phillips, R. & Dement, W. C. (1973). Quantification of sleepiness: A new approach. Psychophysiology, 10, 43 l-436. Home, J.. Brass, C. & Pettitt, A. (1980). Circadian performance differences between morning and evening types. Ergonomics, 23, 29-36. Passouant, P. (1976). Le sommeil un tiers de notre oie. Paris: Stock.
