Kobiety niekoniecznie jak w zegarku

Znowu będzie notka z cytatami. No bo jak inaczej zareagować? Właściwie, to można by było powiedzieć, że ładne kwiatki, i że ręce i inne tam takie opadają. No to mówię. Ale cycaty też dodam, bez nich przecież ani rusz.

Pani Kossobudzka pisze:

Czy istnieją ludzkie feromony? Żaden z naukowców jeszcze nie odważył się tego potwierdzić, ale też niewielu temu zaprzecza.

Nie sądzę, żeby naukowcy tak niezwykle bojaźliwymi jagniątkami byli, że „nie odważają” się czegoś tam powiedzieć. Myślę, że po prostu na razie nie ma wystarczająco dużo przekonujących dowodów (patrz też niżej). Jak będą, to założę się, że laboratoria pobiją się o pierwszeństwo w ich ogłoszeniu. W końcu to feromony przecież, kwestia związana z seksem, i tak dalej.

Ale jeszcze lepsze jest to:

Na razie uczeni nie składają broni i szukają dalej. W tej chwili najpoważniejszym kandydatem na pierwszy ludzki feromon jest związek wydzielany przez kobiety będące przez dłuższy czas w grupie. Wiadomo, że dostosowują one do siebie termin miesiączek i w pewnym momencie wszystkie mają „trudne dni” jednocześnie.

Nie, NIE WIADOMO. Zupełnie nie wiadomo. Owszem, są grupy badaczy, którzy postulują, że synchronizacja cykli u kobiet przebywających razem występuje. Ale są i tacy, którzy twierdzą, że nie ma czegoś takiego. I mają całkiem sporo poważnych zarzutów do tej pierwszej grupy. Parę przykładów:

McClintock(1971) reported that social interaction caused the menstrual onsets for groups of dormitory friends to grow closer together by two days over a four- to-six-month period. Neither McClintock nor subsequent investigators found a tendency for menses to become concordant, but the phenomenon is nonetheless referred to by the misleading term „menstrual synchrony.” In careful analyses, Wilson (1987, 1992) showed that three statistical errors undermine McClintock’s evidence as well as that of subsequent investigators (Graham and McGrew 1980, Quadagno et al. 1981, Preti et al. 1986): (1) failure to correct for the convergence of menstrual onsets by chance, (2) exaggeration of the initial difference in onsets through miscalculation, leading to an erroneous impression of synchronization over time, and (3) possible sampling bias. Strassmann (1990) raised additional concerns having to do with the evolutionary novelty of the study populations (aggregations of young, cycling women) and inconsistencies in the findings across studies, suggesting the possibility of random effects. Moreover, three studies found no evidence for synchrony in Western populations (Jarett 1984, Wilson, Hildebrandt Kiefhaber, and Gravel 1991, Trevathan, Burleson, and Gregory 1993). Despite the dearth of supporting data, many investigators continue to accept the existence of menstrual synchrony rather than confronting the methodological issues Wilson raised (Graham 1991, Weller and Weller 1993). [1]

Menstrual-cycle synchrony among women is a widely held belief. A cursory examination of the menstrual-cycle synchrony literature suggests more studies finding synchrony (McClintock, 1971; Skandhan et al., 1979; Graham and McGrew, 1980; Quadagno et al., 1981; Matteo, 1987; Goldman and Schneider, 1987; Little et al., 1989; Weller and Weller, 1992, 1993a,b, 1995a, 1997a, 1998, 1999a; Weller et al 1995, 1997a) than failing to find it (Jarett, 1984; Trevathan et al., 1993; Wilson et al., 1991; Weller and Weller 1995b, 1998; Weller et al., 1995; Cepicky et al., 1996; Strassmann, 1997). However, the fact that there are a number of studies failing to find synchrony suggests two alternative explanations for these discrepancies. One possibility is that menstrual cycle synchrony is a highly context dependent phenomenon that is far from fully understood (Weller and Weller, 1993c, 1995c, 1997b; McClintock 1998, 2000). Another possibility is that the reports of synchrony are artifacts due to methodological errors interacting with random effects (Wilson, 1992; Strassmann 1997, 1999; Arden and Dye, 1998). Strassmann (1997, 1999) has presented several compelling reasons for suspecting that reports of menstrual-cycle synchrony may be methodological artifacts. First, synchrony reported in the positive studies is very weak; no study has ever shown that women closely match their menses onsets. Second, there is no evidence that synchrony occurs in natural fertility populations where presumably it may have some biological function. Third, and most importantly, cycle variability should be an obstacle to synchrony and cycle variability both within and between women is well documented (Chiazze et al., 1968; Treloar et al., 1967; Vollman, 1977). [2]

Były też kłótnie między autorami niektórych z wyżej wymienionych prac. Weller i Weller pisali w streszczeniu:

On the basis of the results of a computer simulation, Schank (Schank, J.C., 2000. Menstrual-cycle variability and measurement: further cause for doubt. Psychoneuroendocrinology 25, 837-847) argues that our method is biased towards finding synchrony and that the degree of error is an increasing function of cycle variability. We show that Schank’s model is based on unfounded assumptions. Contrary to Schank’s assertion, on which much of the critique is based, there is no evidence that cycle variability is actually large in samples with „state” synchrony. Our reports are valid; and our method is supported both by convergent validity and by the use of statistical „random control” groups. [3]

Jeffrey Schank dyskutował:

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. [4]

Weller i Weller ponownie:

J. C. Schank (2001) argued that biases in the calculation of synchrony (due to inherent variability in the menstrual cycle) and in respondents’ recall of menstrual dates can produce spurious results. In this commentary, the major flaws in J. C. Schank’s arguments regarding the calculation of synchrony are presented. Low standard deviations (< 2.0) of interwomen cycle lengths were found in a reanalysis of the Bedouin family data (A. Weller & L. Weller, 1997). This obviates J. C. Schank’s major assumption that a high degree of cycle variability exists and his concern that high variability produces a spurious increase of onset differences over time. Furthermore, research that has used random control groups has found significantly greater levels of synchrony in their experimental groups, refuting J. C. Schank’s arguments. [5]

A Schank znowu coś znalazł:

The author of this reply argues that A. Weller and L. Weller merely defined away the problem of cycle variability for synchrony by assuming either that all cycles are 28-days long or that the expected difference between 2 cycles is 1/4 the mean of the cycles of 2 rhythms. In her commentary, C. A. Graham stated that A. Weller and L. Weller’s later research did not use recall data, but the author of this reply shows that this is not true. Menstrual-synchrony research taken as a whole is plagued by a multitude of systematic errors that lead inevitably to the conclusion that there is no evidence for menstrual synchrony among women. [6]

Jak widać, inni włączali się także, na „nie” i na „tak”:

J. C. Schank’s detailed discussion of various types of recall biases is inappropriate and misleading given that the majority of menstrual-synchrony studies have used prospective menstrual calendars. The use of menstrual calendars is a well-accepted method in a number of research areas and demands little of participants. J. C. Schank questioned the validity of menstrual calendar data on the basis of assumptions about recall bias for which he had no evidence. [7]

A. Weller and L. Weller (1997) claimed to report „the definitive study of menstrual synchrony” (p. 148). To allow for cycle variability, they used the following criterion for synchrony: It occurred in 2 out of 3 months. The underlying assumption of the state of menstrual synchrony is that cycle length variability is minimal. The present article uses a random selection of cycle lengths from a distribution described by R. F. Vollman (1977) to illustrate how variable cycle lengths cause a fluctuation from synchrony to asynchrony. A. Weller and L. Weller’s (1997) study is not, therefore, conclusive, and future studies of menstrual synchrony should include an assessment of cycle variability as well as onset difference. [8]

A nawet sami Weller i Weller przyznawali:

While many studies have confirmed McClintock’s (1971) finding of human menstrual synchrony, it is also clear that menstrual synchrony does not always occur. [9]

Najnowsze (z 2011 roku) podsumowania podsumowują:

In 1971, Martha McClintock described a social influence on the onset of menses in a study of women living in a college dormitory, who showed an increase in menstrual synchrony of 2 days over a period of four to 6 months (McClintock, 1971). A number of subsequent studies also demonstrated this phenomenon of cycle synchrony and the potential social regulation of ovulation in humans (e.g., Weller and Weller, 1993, 1995, 1997). However, the methods used to detect cycle synchrony have been criticised heavily on theoretical and statistical grounds (Wilson, 1987b, 1992; Strassman, 1997; Arden and Dye, 1998; Schank, 2006; Yang and Schank, 2006), and other studies have failed to find statistically significant patterns of cycle synchrony in either Western populations (e.g., Jarett, 1984; Wilson et al., 1991; Trevathan et al., 1993) or in a natural-fertility population (Strassman, 1997).

Thus, critical reviews of estrous synchrony studies in both humans and non-humans suggest that synchrony has not been demonstrated convincingly and evidence in support of the pheromonal hypothesis is similarly contentious (Schank, 2001c, 2002; Graham, 2002; Weller and Weller, 2002). [10]

Co więcej, jak widać w ostatnim akapicie, wspominają wstrzemięźliwie i o feromonach. Również Strassmann przestrzegała już jakiś czas temu:

In the absence of a theoretical reason for expecting menstrual synchrony to be a feature of human reproductive biology, and until a cycle-altering pheromone has been chemically isolated, it would appear that scepticism is warranted. [11]

To zdecydowanie powinna sobie wziąć do serca pani Kossobudzka. Po prostu, inaczej mówiąc – są różne badania. Są naukowcy, którzy uważają tak, a są i tacy, którzy uważają odwrotnie. Wygląda też na to, że badacze postulujący brak synchronizacji mają bardzo poważne zastrzeżenia co do metodologii, a także i uprzedzeń które, jak piszą, bywały obecne w badaniach tych grup naukowych, które mówią o synchronizacji. Każdy oczywiście może rzucić okiem na prace obu grup i wyrobić sobie własne zdanie. Ale pisanie, w dziale bądź co bądź naukowym Gazety Wyborczej, że „wiadomo”, jest zwyczajnie żenujące.

I jeszcze o cyklach i feromonach:

Stern and McClintock’s (1998) recent finding of ‘definitive evidence of human pheromones’ and ‘confirmation’ of the mechanism underlying ‘menstrual synchrony’ is indeed spectacular. However, they disregarded the methodological critiques (Wilson, 1992; Strassmann, 1997) and negative evidence (Jarett, 1984; Wilson et al., 1991; Trevathan et al., 1993; Strassmann, 1997) that undermine the original report of McClintock (1971), as well as subsequent studies (Graham and McGrew, 1980; Quadagno et al., 1981; Preti et al., 1986). When flawed statistical methods are taken into account, there is scant empirical evidence that the phenomenon of menstrual synchrony exists in the first place.

Popular belief in menstrual synchrony stems from a misperception about how far apart menstrual onsets should be for two women whose onsets are independent. Given a cycle length of 28 days (not the rule—but an example), the maximum that two women can be out of phase is 14 days. On average, the onsets will be 7 days apart. Fully half the time they should be even closer (Wilson, 1992; Strassmann, 1997). Given that menstruation often lasts 5 days, it is not surprising that friends commonly experience overlapping menses, which is taken as personal confirmation of menstrual synchrony. [11]

A już publikowanie – w dziale naukowym – wywiadu z takim ekspertem od feromonów, jakim jest pan sprzedający je w internecie, jest doprawdy kuriozalne. Może warto byłoby sięgnąć raczej do prac naukowych na ten temat. Naprawdę są takie.

Olfactory communication is very common amongst animals, and since the discovery of an accessory olfactory system in humans, possible human olfactory communication has gained considerable scientific interest. The importance of the human sense of smell has by far been underestimated in the past. Humans and other primates have been regarded as primarily ‘optical animals’ with highly developed powers of vision but a relatively undeveloped sense of smell. In recent years this assumption has undergone major revision. Several studies indicate that humans indeed seem to use olfactory communication and are even able to produce and perceive certain pheromones; recent studies have found that pheromones may play an important role in the behavioural and reproduction biology of humans. In this article we review the present evidence of the effect of human pheromones and discuss the role of olfactory cues in human sexual behaviour. [12]

Przydatna literatura:

1. Strassmann, B. (1997). The Biology of Menstruation in Homo Sapiens: Total Lifetime Menses, Fecundity, and Nonsynchrony in a Natural-Fertility Population Current Anthropology, 38 (1) DOI: 10.1086/204592
2. Schank, J. (2000). Menstrual-cycle variability and measurement: further cause for doubt Psychoneuroendocrinology, 25 (8), 837-847 DOI: 10.1016/S0306-4530(00)00029-9
3. Weller L, & Weller A (2002). Menstrual synchrony and cycle variability: a reply to Schank (2000). Psychoneuroendocrinology, 27 (4), 519-26 PMID: 11912003
4. Schank JC (2001). Menstrual-cycle synchrony: problems and new directions for research. Journal of comparative psychology (Washington, D.C. : 1983), 115 (1), 3-15 PMID: 11334217
5. Weller A, & Weller L (2002). Menstrual synchrony can be assessed, inherent cycle variability notwithstanding: commentary on Schank (2001). Journal of comparative psychology (Washington, D.C. : 1983), 116 (3), 316-8 PMID: 12234083
6. Schank JC (2002). A multitude of errors in menstrual-synchrony research: replies to Weller and Weller (2002) and Graham (2002). Journal of comparative psychology (Washington, D.C. : 1983), 116 (3), 319-22 PMID: 12234084
7. Graham CA (2002). Methods for obtaining menstrual-cycle data in menstrual-synchrony studies: commentary on Schank (2001). Journal of comparative psychology (Washington, D.C. : 1983), 116 (3), 313-5 PMID: 12234082
8. Arden MA, & Dye L (1998). The assessment of menstrual synchrony: comment on Weller and Weller (1997) Journal of comparative psychology (Washington, D.C. : 1983), 112 (3) PMID: 9770318
9. Weller L, & Weller A (1995). Menstrual synchrony: agenda for future research. Psychoneuroendocrinology, 20 (4), 377-83 PMID: 8532821
10. Setchell, J., Kendal, J., & Tyniec, P. (2011). Do non-human primates synchronise their menstrual cycles? A test in mandrills Psychoneuroendocrinology, 36 (1), 51-59 DOI: 10.1016/j.psyneuen.2010.06.004
11. Strassmann, B. (1999). Menstrual synchrony pheromones: cause for doubt Human Reproduction, 14 (3), 579-580 DOI: 10.1093/humrep/14.3.579
12. GRAMMER, K., FINK, B., & NEAVE, N. (2005). Human pheromones and sexual attraction European Journal of Obstetrics & Gynecology and Reproductive Biology, 118 (2), 135-142 DOI: 10.1016/j.ejogrb.2004.08.010