Time sense for short intervals during the follicular and luteal phases of the menstrual cycle in humans.

The present study investigated if the time sense (using short intervals) was influenced by the phase of the menstrual cycle. Fourteen women (age: 21.8+/-1.3 years, height: 158.1+/-4.6 cm, body weight: 50.9+/-3.2 kg, mean+/-S.D.) were examined. Their menstrual phase was checked by the participants themselves prior to the study, by measuring oral temperatures after waking but while still in bed over the course of 1-2 months. Participants entered a climatic chamber (26 degrees C, 60% RH, 200 lx) at 09:00 h during either the follicular or luteal phase, and sat quietly on a sofa for 4 h before performing the time sense tests. These used intervals ranging from 1 to 60 s, and consisted of time estimation and time production. In the time estimation test, the participant was required to estimate the interval between two signals provided by buzzers; 10 random intervals were given. For the time production test, the participant was required to produce the interval displayed on a screen by pushing the space key of a computer twice; 10 random intervals were given. The order of testing during the follicular and luteal phases, and of performing the time estimation and time production tests, was counterbalanced. The results indicate that the time sense ran significantly faster during the luteal phases. The findings are discussed in terms of a higher load error between the actual core temperature and its thermoregulatory set-point during the luteal phase of the menstrual cycle.