Including neither-type in the morningness-eveningness dimension decreases the robustness of the model

The present paper is a study of axillary temperature and performance during the waking part of the day and the relationship of these two variables to Morningness-Eveningness preferences. A reduced scale of the Horne and Ostberg questionnaire was adapted and standardized for the Spanish population, and 3 groups of subjects were formed (Morning-types: 3 men, 2 women; Neither-type: 3 men, 6 women; Evening-types: 1 man, 4 women). Three different tasks were tested, auditory reaction time (to measure alertness and speed), index finger tapping (motor skill), and verbal memory (information processing). The subjects were tested hourly in 13 sessions spread out over the day. Morningness-Eveningness preference groups did not differ in temperature and performance. Neither-type subjects did not present values intermediate between those of the Morning- and Evening-types.