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Effects of phases of menstrual cycle on signal detection and complex reaction time

Regarding the concentration of estrogen and progesterone menstrual cycle is usually divided in five different phases, i.e. pre-menstrual, menstrual, follicular, ovulatory and luteal. Although level of estrogen may affect the state of organism, including the level of activation, it has effects on general efficiency. It may be expected, therefore, that efficiency will be different in various menstrual phases. The aim of this study was to find out possible effects of menstrual phases on signal detection and complex reaction time. The investigation included 12 female subjects (20-23 years of age) with regular menstrual cycle lasting around 28 days. Every subject in each menstrual phase performed a signal detection task, as well as a complex reaction task. The signal detection task was computer presented, classical Mackworth cloc task, were the signal was double jump of the hand, which appeared in irregular time intervals during 20 minutes experimental session. When the signal appeared, the computer started counting time, which stopped when the subject pressed the space key on the key board. The time was taken as the subject’s reaction time to the correct signal. Missed signals were also recorded during the signal detection session. The complex reaction task constited of a computer presented stimulus scheme 3+3 squares where the stimulus randomly appeared in the eight peripheral squares. The subject had to respond, as quicly as she could, on: a) corresponding key on numeric part of the key board, b) one key to the left, c) two keys to the left of the corresponding key. Every subject had 10 trials in each of the three situations. The mean time of the 10 trials was taken as thesubjects complex reaction time for the given situation. Apart from this, after 10 trials in each situation the subject had to assess the difficulty of just performed task on Borg'’ scale. As could be expected, the results showed an increase in signal reaction time during the 20 minute detection period. The results also showed the effects of menstrual phases on signal reaction time, as well as complex reaction time. The shortest time in the both tasks were obtained in ovulatory phase, while the longest times were observed in menstrual phase. As the same time, the complex reaction tasks were assessed more difficult in the later phase then the former. The differences in the efficiency may be attributed to the differences in estrogens levels.

signal detection; menstrual cycle

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