Menstrual synchrony and cycle variability: a reply to Schank (2000).

Area of Science:

• Reproductive biology
• Human physiology
• Statistical analysis in biology

Background:

• Menstrual synchrony, the alignment of menstrual cycles among women, can be studied as a process over time or a state of existing alignment.
• Previous research proposed a method to quantify "state" menstrual synchrony.
• A critique suggested this method is biased and sensitive to menstrual cycle variability.

Purpose of the Study:

• To address and refute criticisms regarding the "state" menstrual synchrony measurement method.
• To demonstrate the validity and reliability of the proposed method for assessing menstrual synchrony.

Main Methods:

• Analysis of a computer simulation model used in prior critiques.
• Examination of assumptions regarding menstrual cycle variability in synchronized groups.
• Validation through convergent validity and the use of statistical random control groups.

Main Results:

• The critique's model was found to be based on unfounded assumptions.
• Evidence does not support the claim of large menstrual cycle variability in "state" synchrony samples.
• The proposed method for measuring "state" menstrual synchrony was demonstrated to be valid.

Conclusions:

• The method for calculating "state" menstrual synchrony is scientifically sound and reliable.
• Previous criticisms regarding bias and cycle variability are unsubstantiated.
• The study reaffirms the validity of its findings on menstrual synchrony.