Menstrual synchrony by chance when there is menstrual cycle variability. Yang and Schank argued that when there is cycle variability (i.e., either women have irregular cycles, have cycles of different frequencies, or both), most women will have the opportunity to experience synchrony even though it is a result of cycle variability and not a result of a mechanism such as the exchange of pheromones. For example, consider two women A and B. Suppose A has menstrual cycles that are 28 days long and B has cycles that are 30 days long. Suppose further that when A and B become close friends, B
Immune cycle Immune cycle The immune cycle is a natural homeostatic oscillation of the immune system when chronic inflammation is occurring. Similar to the menstrual cycle, the exact wavelength and waveform of each particular individual patient is different. That is, different people have different immune cycles although each cycle is typically repeated every seven days. C-reactive protein levels in the blood need to be measured every few days in order to have enough time points to show a repeating fluctuation (a wave-like cycle). This is caused by the synchronous division of T cells over time, with T-effector cells boosting immune activity followed