Composite scales of morningness andpreferences: Preliminary validity data in

Peruvian undergraduates

J. F. DIAZ-MORALES* and M. P. SANCHEZ-LOPEZ

Departamento de Psicologıa Diferencial y Psicologıa del Trabajo, Facultad de Psicologıa,

Universidad Complutense de Madrid, Campus de Somosaguas, s/n, 28223, Madrid,

Spain

The aim of this study is to offer preliminary results about the validity of the

composite morningness scale (CS) and the early/late preferences scale (PS) in

a Peruvian sample. The relationship of both scales with the preferred rising

and retiring times was analysed, along with the level of self-reported

alertness. In Bohle et al.’s (2001) work, the relationship between morningness

and preferred rising and retiring times was higher over the weekend than on

weekdays. This difference explained the dispositional nature of morningness,

due to the possible lesser influence of time schedules over the weekend in

individuals’ preferences. This result is replicated in a group of 139 Peruvian

undergraduates, aged between 18 and 29 years (M=21.73), of whom 78.4%

were women. The relationship between morningness and (actual) normal

rising and retiring times on weekdays and over the weekend is considered.

The results partially confirm Bohle et al.’s (2001) hypothesis about preferred

rising and retiring times and their relationship with the PS, and actual rising

time and its relationship with the CS and PS. The differences in the level of

self-reported alertness between morning, intermediate and evening-oriented

groups provide support for the validity of both scales. Finally, the scores of

CS and PS in Peruvian undergraduates are similar to those found by Smith et

al. (2002) in university students from six countries.

Keywords: Morningness – eveningness; Time-of-day; Actual and preferred

wake – sleep behaviour; alertness.

1. Introduction

Freeman and Hovland (1934) and Kleitman (1939) indicated that most people can be

differentiated along a continuum ranging from low morningness (or high eveningness) to

high morningness (or low eveningness). At this time, in the 21st century, Natale and

Cicogna (2002) analysed data to determine whether morningness – eveningness is really a

*Corresponding author. Email: juanfcodiaz@psi.ucm.es

Ergonomics, Vol. 48, No. 4, 15 March 2005, 354 – 363

ErgonomicsISSN 0014-0139 print/ISSN 1366-5847 online # 2005 Taylor & Francis Group Ltd

http://www.tandf.co.uk/journalsDOI: 10.1080/0014013042000327661

continuum, finding that the differential characteristics of morning and evening-oriented

individuals emerge, without necessarily taking into account the extreme ‘types’ (clearly

morning or evening orientated).

Individual differences in the circadian rhythm are the underlying mechanism of this

continuum (Kerkhof 1985). Circadian rhythms are cycles of approximately 24 h that have

been identified by analysing biological variables (for example, body temperature and levels

of hormone secretion) and also by studying behavioural variables, such as performance of

various tasks, mood or physical exercise (Folkard and Monk 1985; Smith et al. 1997). It is

considered that preference for performing activities at different times of day, mainly in the

morning or in the evening, is a reliable index of these individual differences in circadian

rhythm (Kerkhof 1985). This individual difference in circadian variability is called

morning vs. evening orientation or, more simply, ‘morningness’. Thus, the creation and

adaptation of scales or inventories to determine people’s circadian orientation has been

the focus of much of the research in this area, as the use of applied questionnaires (e.g. for

personnel selection for night shifts) seems more practical than other more rigorous

assessment procedures (for example, assessment of rectal temperature, hormone level in

blood, etc.), which are not very practical because of their high cost.

The most well-known questionnaire is the one created by Horne and Ostberg (1976),

the morningness – eveningness questionnaire (MEQ). Subsequently, other questionnaires

were developed, such as the circadian type questionnaire by Folkard et al. (1979), the

diurnal type scale (DTS) by Torsvall and Akerstedt (1980), or the Mauburger

questionnaire (Moog 1981). In order to obtain a reliable and valid measurement of

morningness that would overcome the psychometric deficiencies of the former scales,

Smith et al. (1989) created the composite scale of morningness (CS) using the best items

from the MEQ and the DTS. Other proposals have subsequently appeared: the reduced

version of the MEQ (Adan and Almirall 1991); the morningness scale adapted to persons

with an elemental reading level (basic language morningness scale, BALM), which is a

simplified version of the CS (Brown 1993); the early/late preferences scale (PS) created by

Smith et al. (1993) to improve some aspects of the CS; or the lark – owl chronotype

indicator (LOCI) by Roberts and Irvine (1999).

The CS has been translated into French (Caci et al. 1999), Thai (Pornpitakpan 1998,

2000) and Italian (Natale and Alzani 2001). Studies with Spanish (Martın 1989, Dıaz

Ramiro 2000, Dıaz-Morales and Aparicio 2003, Dıaz-Morales and Sanchez-Lopez 2004,)

and Argentine populations (Sanchez-Lopez and Dıaz-Morales 2001) have revealed

adequate reliability of the CS. In the Peruvian population, Dıaz-Morales et al. (2005) also

obtained satisfactory psychometric indices. In general, the results of these studies indicate

that the CS can be used in Spain, Argentina and Peru insofar as reliability (internal

consistency) is concerned. However, its validity has not yet been evaluated, although this

aspect has been sufficiently addressed in other languages (Smith et al. 1989, Greenwood

1994, Guthrie et al. 1995).

Smith et al. (1993) created the PS to resolve some of the problems of the CS; the use of

different response scales in some of the items and the inconvenience of referring to specific

times of day. Therefore, the PS, which has a more consistent and less complex response

format, is more appropriate to assess the morningness of people who have atypical or

irregular sleeping habits.

Currently, the CS and the PS are considered to be two of the most reliable and

valid scales to measure morningness (Bohle et al. 2001, Smith et al. 2002, Zickar et al.

2002). Bohle et al. (2001) analysed both scales in a sample of university students,

concluding that neither of them is clearly superior as far as psychometric properties

Composite scales of morningness and preferences 355

(internal consistency and temporal stability) are concerned. Smith et al. (2002) tested

the hypothesis of equality of factor form and factor loadings of the CS and the PS in

six countries. The results indicate an invariant bifactor structure for both scales, which

allows comparison of the means in the morningness factors in each of the countries

studied. In addition, both scales showed adequate psychometric indices (reliability and

validity) in the six countries. Zickar et al. (2002) studied the discrimination capacity of

the items from the two scales. Most of the items have very acceptable and useful

indices for differentiating morningness from eveningness orientation. Both the scales

are adequate when their items are analysed from the viewpoint of item response

theory. However, the items about preferred rising time are more closely related to the

latent morningness construct than are items that assess peak performance or retiring

time.

University students have participated in most of the studies that analyse the

psychometric properties of the scales to assess morningness – eveningness. The

university population is adequate because their circadian rhythms are not so much

under the influence of time schedules and social patterns as those of the adult working

population. Most occupations involve dedicating a large part of the day to work,

which affects life habits and, as has been noted in various studies (Mecacci and Zani

1983, Park et al. 1997), produces a higher tendency toward morningness. According to

Bohle et al. (2001), when university students are asked about their preferred rising and

retiring times (‘if you were totally free to choose’), a difference between these wake –

sleep behaviours on weekdays and over the weekend can be established. The latter are

‘free’ from the possible influence of study or work schedules. Therefore, as

morningness is considered a disposition, it is not surprising to find that sleeping

preferences over the weekend are more related to morningness. The first objective of

this study was to examine if the greatest relationship showed by Bohle et al. between

morningness and preferred rising and retiring times during the weekend was also

found with normal (actual) rising and retiring times. The second research objective

was to analyse the relationship of the CS and the PS with the level of perceived

alertness, one of the variables with which morningness has the highest relationship

(Kerkhof 1985).

2. Method

2.1. Participants

One hundred and thirty-nine students from the city of Lima (Peru) participated in this

study. There were 109 (78.4%) women and 30 (21.6%) men. The mean age was 21.73

years (SD=2.63, range=18 – 29). Most of the students attended classes at different

times of the morning or the afternoon, without having a strict study schedule.

2.2. Measurement instruments

2.2.1. Composite scale of morningness (Smith et al. 1989). The CS is a 13-item scale

with a Likert-type response format. Five of the elements of the scale refer to different

times of the day. The score is obtained by the sum of the items and ranges from 13

(extreme eveningness) to 55 (extreme morningness). Greenwood (1994), Guthrie et al.

(1995) and Smith et al. (1989) provide adequate data about both reliability and

validity. The CS was translated into Spanish by Dıaz Ramiro (2000). This version was

356 Juan F. Dıaz-Morales and Marıa P. Sanchez-Lopez

used on a sample of university students and adults, revealing excellent psychometric

properties: Cronbach’s a coefficient of 0.90 and a high correlation (r=0.79) with the

MEQ by Horne and Ostberg (1976). In subsequent studies, its reliability and validity

have been corroborated for Spanish-speaking populations. For example, an acoefficient of 0.75 was obtained in the Argentine population (Sanchez-Lopez and

Dıaz-Morales 2001), and an a of 0.85 was obtained in the Spanish population (Dıaz-

Morales and Sanchez-Lopez 2004).

2.2.2. Early/late preferences scale (Smith et al. 1993). The PS is made up of 12 items that

do not refer to specific times of day, but to persons’ preference for performing various

activities, and comparing them with their reference group. The score of this scale is

calculated by adding all the items, and ranges from a minimum of 12 (extreme

eveningness) to a maximum of 60 (extreme morningness). In addition to the 12 elements

that comprise the scale, two items have been included: ‘In general, when do you feel most

active?’ and ‘In general, when do you feel at your best?’ The response scale of these two

items is the same as for the remaining elements of the PS. These items were included by

Bohle et al. (2001) and are used in the current study for comparative purposes. The PS

was translated into Spanish by the authors of this study. A pilot study was carried out

with a group of university students who analysed item wording and comprehensibility.

An a coefficient of 0.83 was obtained by Dıaz-Morales and Sanchez-Lopez (2004) in an

undergraduate population.

2.3. Other measurements: Sleeping behaviour and subjective alertness level

As morning and evening types differ in their sleeping habits (Kerkhof 1985),

participants were asked to indicate their preferred and habitual rising and sleeping

behaviour on weekdays and over the weekend. In addition, participants had to

estimate how alert they felt on a day when they had no important responsibilities.

Ratings were provided at 2-h intervals, from 06:00 until 02:00, on a 9-point Likert-

type scale (higher scores indicate a higher level of alertness). ‘Subjective alertness is

probably the most powerful and repeatable of all the circadian rhythms of

psychological process’ (Natale and Cicogna 1996) and, therefore, it is the best

criterion to use as evidence of the external validity of morningness and was included

in this study to compare the results with those obtained by Bohle et al. (2001).

According to Bohle et al. and Smith et al. (2002), these measurements are additional

indicators of morningness – eveningness and are used as a preliminary assessment of

the validity of the PS and CS.

2.4. Procedure and data analysis

The scales were administered by the first author during the students’ normal classes in the

month of June. Administration was carried out in groups; some groups were assessed in

the morning and others in the afternoon. Participation was voluntary and participants

were informed about their results. The data were analysed by means of basic descriptive

statistics (e.g. means, standard deviations and cut-points). Scale normality was analysed

by means of the Kolmogorov-Smirnov test. Student’s t-test was used to calculate gender

differences across groups and Pearson’s correlation to analyse the relationships between

morningness and sleeping behaviours. Data analyses were carried out with the SPSS 11.5

statistical package.

Composite scales of morningness and preferences 357

3. Results

3.1. Descriptive statistics

The group mean for the CS was 33.88 (SD=6.24, range=16 – 51). The distribution of

the scale was normal (Kolmogorov-Smirnov’s Z=0.76, p=0.61). The group mean of

the PS was 35.02 (SD=7.09, range=15 – 54) and its distribution was normal

(Kolmogorov-Smirnov’s Z=0.92, p=0.35). No gender differences were observed either

in the CS (t (137)=0.83, p=0.403), or in the PS (t (137)=0.86, p=0.387). The scales

were highly correlated (r=0.83), which suggest that there is considerable overlap

between them.

The Peruvian university students showed very similar scores to those obtained by

Smith et al. (2002) for the CS in a group of Spanish university students (M=33.9,

SD=5.8), and much lower than those obtained by Colombian university students

(M=42.4, SD=5.7). The same tendency was observed in the PS: the Peruvian

university students showed similar values to those obtained by Smith et al. in a group of

Spanish university students (M=36.4, SD=6.0) and to those obtained by Bohle et al.

(2001) in Australian university students (M=35.1, SD=7.1), but a lower tendency

towards morningness than the Colombian university students (M=39.4, SD=6.2).

3.2. Relationships with other measurements

The correlation between morningness and perceived level of arousal (‘feel most active’)

was similar in both scales (r=0.63 and 0.58 for the CS and the PS, respectively), as was

the relationship between morningness and ‘feeling at one’s best’ (r=0.62 and 0.67 for the

CS and the PS, respectively).

Tables 1 and 2 show the results obtained in this study and those found by Bohle et al.

(2001). All the correlations were significant (p5 0.001), except for the correlations

between preferred and actual rising times on weekdays and the PS in the present study.

When performing the same comparison as Bohle et al. (2001), a higher relationship was

found between morningness and the preferred rising and retiring times over the weekend

than on weekdays for the PS ( – 0.47 and – 0.31 for rising and retiring times over the

weekend vs. – 0.38 and – 0.14 on weekdays, respectively). The CS showed a similar

relationship with the preferred rising time on weekdays and over the weekend ( – 0.58 and

– 0.60, for weekdays and weekends, respectively) and, in contrast to the results of Bohle et

Table 1. Comparison of the correlations of the composite morningness scale (CS) and theearly/late preferences scale (PS) and preferred rising/retiring times on weekdays and over the

weekend obtained in the present study and in Bohle et al. (2001)

Weekdays Weekends

Preferred rising time Preferred retiring time Preferred rising time Preferred retiring time

Scales

Present

study BohleaPresent

study BohleaPresent

study BohleaPresent

study Bohlea

CS – 0.58 0.45 – 0.36 0.40 – 0.60 0.68 – 0.19 0.52

PS – 0.38 b 0.43 – 0.14 0.39 – 0.47 0.65 – 0.31 0.49

a In Bohle et al. (2001), higher scores indicated eveningness orientation. Therefore, their correlations are

positive, whereas those from the present study are negative.b Except for this correlation, the remaining correlations were significant at p5 0.001.

358 Juan F. Dıaz-Morales and Marıa P. Sanchez-Lopez

al., a lower correlation with the preferred retiring time over the weekend ( – 0.36 vs. – 0.19,

for weekdays and weekends, respectively). The CS revealed somewhat weaker relation-

ships than those found by Bohle et al. (2001) (except for the relationship with preferred

rising time on weekdays). The correlation between the PS and the preferred retiring time

on weekdays was the weakest.

Following Bohle et al.’ s (2001) hypothesis, which considers morningness a

dispositional variable and predicts higher correlations with preferred waking and

sleeping preferences over the weekend, the participants were asked two more questions

about their actual rising and retiring times on weekdays and over the weekend (see table

2). The correlations between both the CS and the PS and the students’ actual rising times

were higher over the weekend, whereas the correlations of the scales with actual retiring

times were similar on weekdays and over the weekend.

Bohle et al.’s (2001) hypothesis seems to be confirmed for the PS and preferred rising

and retiring times over the weekend (vs. on weekdays), and for both the CS and the PS in

regard to the actual rising time over the weekend (vs. on weekdays).

3.3. Relationship with perceived alertness level

Figure 1 displays the levels of alertness of morning, intermediate and evening ‘types’

during waking hours, using the 10th and 90th percentiles of the CS (25 and 42

respectively). The morning group reported a higher level of alertness in the 08:00 – 10:00

interval and a progressive decrease beginning in the 18:00 – 20:00 interval. The evening

group reported their highest subjective alertness level during the 20:00 – 22:00 interval,

with an increasing pattern starting at the 14:00 – 16:00 interval. When the scores obtained

on the PS (percentiles 10th and 90th are 26 and 43, respectively) are used to establish the

three ‘chronotypes’, the same tendencies and maximum and minimum values emerge as

for the CS, although the intermediate and morning groups are not so differentiated as

when using the CS (see figure 2).

4. Discussion

This study provides new data about the validity of the PS and the CS. The results

obtained in the Peruvian population are similar to those found by Bohle et al. (2001) in

Australian university students and by Smith et al. (2002) in university students from six

countries. The mean values on the morningness scales are within the ranges found by

Smith et al. with very similar variability as indicated by the standard deviations.

The validity of both scales in the Peruvian population is adequate. The relationship

between the scales is higher than the range of correlations found by Smith et al. (2002) in

six countries (r=0.69 – 0.82), and is similar to the value obtained by Zickar et al. (2002)

Table 2. Correlations of the composite morningness scale (CS) and the early/late preferencesscale (PS) and actual rising/retiring times on weekdays and over the weekend

Scales Weekdays Weekends

Rising time Retiring time Rising time Retiring time

CS – 0.37 – 0.47 – 0.63 – 0.45

PS – 0.17a – 0.31 – 0.46 – 0.34

aExcept for this correlation, the remaining correlations were significant at p5 0.001.

Composite scales of morningness and preferences 359

Figure 1. Alertness ratings by time of day for the composite scale of morningness.

Figure 2. Alertness ratings by time of day for the early/late preferences scale.

360 Juan F. Dıaz-Morales and Marıa P. Sanchez-Lopez

(r=0.87). The results of Bohle et al. (2001) concerning morningness and preferred rising

and retiring times on weekdays and over the weekend have been partially replicated. They

are similar to those found by Bohle et al. for the PS, but not for the CS. One possible

explanation is that some items of the CS (e.g. social activities and meeting friends or

evening meal) can be ‘strongly influenced by social and cultural expectations, and less by

biological or behavioural disposition as morningness’ (p. 896). The PS, whose items do

not refer to specific times of day but rather to a comparative judgment, may be more

related to a dispositional variable such as morningness.

Participants were also asked to indicate their actual rising and retiring times on

weekdays and over the weekend. The results only support Bohle et al.’s (2001) hypotheses

regarding the CS and the PS for rising time. In this case, when taking the actual times into

account, a higher relationship between morningness and rising time over the weekend is

observed. Koscec et al. (2001) indicated that, assuming more freedom for university

students to organize their habitual activities, actual behaviour may reflect morningness or

eveningness to a greater extent than intentions or preferred behaviours. The 12 items

from the student MEQ, created by Koscec et al., refer to daily habits and usual

behaviours, more than to preferred habits or behavioural intentions.

The importance of the actual rising time and its relationship with morningness was

revealed by Zickar et al. (2002), who verified that items referring to the time when people

wake up in the morning differentiate morningness and eveningness orientation better

than do items referring to when people retire or to peak performance. These authors

postulate that it may be appropriate to add items to the PS referring to the time a person

wakes up in the morning. The importance of this type of behaviour is also emphasized by

Natale and Cicogna (1996), who conclude that, in order to differentiate morning and

evening-oriented persons, the transition from sleeping to waking is more representative

than the transition from waking to sleeping when considering alertness. The distinction

between actual and preferred habits should be considered in future studies, using another

type of non-university population, in which the influence of external social factors (e.g.

work schedules) on the relationship between actual/preferred habits and morningness is

analysed.

The differences between morning-, intermediate and evening-oriented groups in

perceived level of alertness are very similar to those found by Bohle et al. (2001) and by

Smith et al. (2002). Morning-oriented groups are more alert in the morning than are

intermediate and evening-oriented groups, whereas the latter reach peak alertness in the

afternoon. It was found that the pattern of perceived level of alertness over the day

(specifically, during the afternoon) is more similar in morning- and intermediate-oriented

groups when using the PS. This may be due to the reduced number of participants in this

study. Nonetheless, the authors consider that these results are in accordance with those

obtained by Bohle et al. and Smith et al. with a higher number of participants.

Lastly, the mean levels of the CS and the PS were compared with the results obtained in

other university groups from various countries, assuming that both scales measure a

unidimensional construct of morningness. The findings suggest that cultural differences in

circadian variation seem to exist, but the explanation of these differences is more complex

than the consideration of measures not referring to specific times (e.g. PS). The mean

scores in CS and PS are similar between Peruvian and Spanish undergraduates of Smith

et al. (2002), but very different from Colombian students. However, recently, other results

in a Spanish population were obtained (Dıaz-Morales and Sanchez-Lopez, 2004). The

undergraduates taking part in this study showed a greater tendency to eveningness

(M=28.9 for CS and M=33.5 for PS) compared with the Spanish subsample used by

Composite scales of morningness and preferences 361

Smith et al. Future research must clarify these discrepant results in a Spanish population.

A further issue is to determine whether the structure of the scales is identical in the

various countries compared, as stated by Smith et al. (2002). If the factor structure is

invariant in different countries, then one could compare the results obtained, knowing

that the compared factor(s) are identical in both populations and, therefore, comparable.

However, this does not invalidate taking the total score of the CS into account, as was the

case in the current study and in previous works (e.g. Greenwood 1994, Pornpitakpan

1998, 2000). Future studies should nonetheless address this issue, also taking into account

other aspects of the validity of the scales, such as their predictive validity and the

influence of social factors.

Acknowledgements

The authors thank Professors Cecilia Thorne, Karem Dıaz, Doris Argumedo and Monica

Iza who made the data collection during the research stay of the first author.

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