Menstrual-cycle synchrony: Problems and new directions for research.

Abstract

Since M. K. McClintock (1971) published the 1st study on menstrual synchrony among women, a number of other studies have also reported synchrony using a variety of methods. The most recent reports of synchrony come from A. Weller, L. Weller, and colleagues, and their findings of synchrony have been getting stronger (by their own account). In this article, the author analyzes their new methodology and presents 2 simulation studies that demonstrate how biases and errors can produce synchrony as an artifact. Two mutually reinforcing categories of errors are identified: (a) errors in calculating the expected mean onset difference between cycles when there is cycle variability and (b) errors that may result from allowing participants to fill out menstrual-cycle-onset calendars, including recall biases and the mutual exchange of information. It is suggested that synchrony may be a biological state to be avoided and that cycle variability may facilitate female mate choice.

Chemosignals, hormones and mammalian reproduction

“…Such an effect was reported for humans (Stern and McClintock, 1998) and has been inferred in earlier studies reporting synchrony in humans (Weller and Weller, 1993). However, other studies or re-analysis of previous studies, have found no evidence of cycle synchrony in humans (Schank, 2001b; Strassmann, 1999; Whitten, 1999; Wilson, 1987, 1992), non-human primates (chimpanzee: (Matsumoto-Oda et al, 2007); Mandrill: (Setchell et al, 2011); macaque (Furtbauer et al, 2011)), rats (Schank, 2001a) or hamsters (Schank, 2000). It might be that cycle synchrony occurs only in very restricted and contextually-specific circumstances (McClintock, 2002) but, on balance, the evidence suggests that ovarian synchrony does not exist as a biologically meaningful phenomenon (Schank, 2001b, 2006).…”

Assessing female sexual arousal with the labial thermistor: Response specificity and construct validity

“…Menstrual cycle and hormonal birth control use have been noted to affect labial temperature, possibly through inconsistent habituation to repeated sexual stimuli (Slob et al, 1991). Although limited menstrual cycle and medication data were collected in this study, the information gathered was insufficient to adequately control or test the possible effects of either (Schank, 2001;Graham, 2002). Similarly, the effects of parity on genital sexual response are not well-characterized, and these data do not address potential variability due to childbirth experience.…”

Neuroendocrinology of Reproduction

“…284 However, supportive research has been criticized on methodological grounds, and the existence of this phenomenon remains controversial. 285 Also, while the vomeronasal organ-believed to be responsible for pheromone detection in animals-develops in utero in humans, it subsequently regresses and is largely believed to be nonfunctional in adults. 286 …”