Kalebić K., Šimić N. (2000): Changes in signal detection and complex reaction
times during the menstrual cycle. XII. Dani psihologije u Zadru, Sažetci radova,
32.
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. Level of
estrogen may affect the state of organism, including the level of activation which has effects
on general efficiency. It is reasonable to expect that performance may be affected by
hormonal changes, therefore the efficiency could differ amongst the five phases. The aim of
this study was to find out possible effects of menstrual phases on signal detection time and
complex reaction time. The investigation included 12 female subjects with regular menstrual
cycle lasting around 28 days. Every subject in each phase performed a signal detection task,
as well as a complex reaction task. The signal detection task was the classical Mackworth’s
clock task. The task was computer generated and presented, where the signal was double
jump of the hand, which appeared at random during 20 minutes of experimental session. The
subject’s reaction times to the correct signals as well as number of missed signals were
recorded during the signal detection session. The complex reaction task consisted 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 possible, to the: a)
corresponding key on numeric part of the key board, b) first key to the left, c) second key to
the left from the corresponding key. After 10 trials in each situation the subject had to assess
the difficulty of just performed task on 21 point Borg’s scale. As could be expected, the
results showed an increase in correct 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 times in both tasks were obtained in the ovulatory
phase, while the longest times were observed in the menstrual phase. At the same time, the
complex reaction tasks were assessed more difficult in the latter phase than the former. The
differences in efficiency may be attributed to the differences in estrogens levels and its effects
on mood and behaviour.