Mutual Exchange of Information

In his 2001 article, Schank suggests the following:

“Consider a typical research scenario in which participants are close friends who live together, sisters, or mother and daughters. If the filling out of calendars is not checked by researchers on a regular basis, participants may forget to fill out their calendars for a few days or weeks. One participant filling out a calendar may remind others (e.g., roommates, sisters, and mothers) to fill out their calendars. Thus, scenarios are clearly possible (when there are insufficient control procedures) for participants to fill out calendars at the same time and together. If, in addition, it has been a few weeks since they last filled out their calendars, they may discuss among themselves when their menstrual cycle onsets occurred. One roommate or sister may remember that her last onset was on a Saturday, and if the other roommate, sister, or mother recalls that she too was menstruating on a Saturday, they may both mark it down on their calendars as the same day even though their cycle onsets were actually a Saturday apart.”

Cynthia Graham, a researcher now at Indiana University, argues in her reply to Schank that:

“Although authors may be criticized for not providing a fuller account of the procedures used to gather menstrual cycle data, a number of the studies Schank cites did use procedures to reduce the likelihood that women would complete calendars retrospectively. At least two studies (Matteo, 1987; L. Weller, Weller & Avenir, 1995) contacted women to remind them to fill out menstrual calendars. Little et al. (1989) emphasized to their participants that they should not discuss their diaries. In our own study, we gave women an explanatory letter with instructions on how to complete the diary and also asked them to draw a line through a calendar, if they forgot to record menses, rather than make entries retrospectively (Graham & McGrew, 1980). Studies have acknowledged that a proportion of women did not provide complete menstrual data (e.g. Little et al., 1989; L. Weller, Weller & Avenir, 1995; L. Weller, Weller & Roizman, 1999). Thus, the scenario that Schank presents of women “helping each other to recollect their menstrual cycle onsets” (p. 11) is indeed speculative.”

Schank in turn responds that:

“Most importantly, menstrual synchrony studies have differed from other areas of research requiring friends and roommates, mothers and daugthers to fill out separate calendars, and yet none of Weller and Weller’s (2002) studies have implemented controls for the mutual exchange of information. I showed that even very small systematic errors due to either the mutual exchange of information or recall could produce the synchrony effects reported by Weller and Weller (e.g., 1997a). To argue that a study is confounded does not require proving that it was confounded, but merely that confounding variables such as recall and the mutual exchange of information were not controlled.”

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