Evaluation

• Evolutionary basis - strength - evolutionary basis is a strong argument as it is a scientific theory eg. menstrual synchronisation observed in stern and mcclintocks study is thought to have some evolutionary value. For our ancestors, it may have been advantageous to menstruate together as it would allow babies whos mothers died due to childbirth to have access to breastmilk. This suggests synchronisation to be an adaptive strategy.
• x-methodological limits - There are many factors that may affect change to the menstrual cycle including stress, diet and exercise. These may act as confounding variables. this means that any supposed patterns of synchronisation which may have occurred by chance. This could explain the failure of other studies (eg. Trevathan 1993) and the failure to replicate findings. This suggests that menstrual synchrony studies may be flawed.
• Real world application - One effective treatment for seasonal affective disorder is light therapy. This consists of a box which emits light at a specific wavelength to reset the body's internal clock. Studies show this has been effective in treating SAD in 80% of people (Sanasi 2014). It is also preferred over anti-depressants because it is regarded as safe. But it can produce headaches and eye-strain (Rohan 2009) recorded a relapse rate of 46% over successive winters compared to 27% in those doing CBT.