[DanaC]

From the first link:

On page 91 of The Female Brain, Dr. Louann Brizendine writes (emphasis added):


Males have double the brain space and processing power devoted to sex as females. Just as women have an eight-lane superhighway for processing emotion while men have a small country road, men have O'Hare Airport as a hub of processing thoughts about sex whereas women have the airfield nearby that lands small and private planes. That probably explains why 85 percent of twenty- to thirty-year-old males think about sex every fifty-two seconds and women think about it once a day -- or up to three or four times on their most fertile days.

This striking different in rates of sexual thoughts is also one of the bullet points on the book's jacket blurb -- but there, female sex-thought frequency is downgraded from "once a day" to "once every couple of days":

•Thoughts about sex enter a woman's brain once every couple of days but enter a man's brain about once every minute

Whatever the exact numbers, it's an impressive-sounding difference -- scientific validation for a widespread opinion about what men and women are like. And this is interesting stuff, right at the center of social and personal life, so you're probably wondering about the details of the studies that produced these estimates.

The end-notes for the quoted segment from p. 91 yield the following references:

1. Bancroft, J. (2005). "The endocrinology of sexual arousal." J Endocrinol 186(3): 411-27
2. Laumann, E. O., A. Paik, et al. (1999). "Sexual dysfunction in the United States: Prevalence and predictors." JAMA 281(6): 537-44.
3. Laumann, E. O., Nicolosi, et al. (2005). "Sexual problems among women and men aged 40-80: Prevalence and correlates identified in the Global Study of Sexual Attitudes and Behaviors." Int J Impot Res 17(1): 39-57.
4. Lunde, I., G.K. Larsen, et al. (1991). "Sexual desire, orgasm, and sexual fantasies: A study of 625 Danish women born in 1910, 1936 and 1958." J Sex Educ Ther, 17:62-70.

As per this series of blogs, the author now examines in depth both the claims and the evidence. beginning with reading the cited papers. I'll not post all of them, but here's what two of the sources have to say, and how they relate to the studies they've been cited in:

1. The abstract for Bancroft (2005) begins:


The relevance of testosterone, oestradiol and certain peptides (oxytocin (OT), ß-endorphin and prolactin (PRL)) to sexual arousal in humans is reviewed. In addition to behavioural studies, evidence of distribution of gonadal steroid receptors in the brain and the limited evidence from brain imaging are also considered.

These two sentences are a good summary of the paper as a whole, which says nothing whatever about how often women or men think about sex.

2. The abstract for Laumann (1999):


Context While recent pharmacological advances have generated increased public interest and demand for clinical services regarding erectile dysfunction, epidemiologic data on sexual dysfunction are relatively scant for both women and men.
Objective To assess the prevalence and risk of experiencing sexual dysfunction across various social groups and examine the determinants and health consequences of these disorders.
Design Analysis of data from the National Health and Social Life Survey, a probability sample study of sexual behavior in a demographically representative, 1992 cohort of US adults.
Participants A national probability sample of 1749 women and 1410 men aged 18 to 59 years at the time of the survey.
Main Outcome Measures Risk of experiencing sexual dysfunction as well as negative concomitant outcomes.
Results Sexual dysfunction is more prevalent for women (43%) than men (31%) and is associated with various demographic characteristics, including age and educational attainment. Women of different racial groups demonstrate different patterns of sexual dysfunction. Differences among men are not as marked but generally consistent with women. Experience of sexual dysfunction is more likely among women and men with poor physical and emotional health. Moreover, sexual dysfunction is highly associated with negative experiences in sexual relationships and overall well-being.
Conclusions The results indicate that sexual dysfunction is an important public health concern, and emotional problems likely contribute to the experience of these problems.


There is nothing at all in this paper about how often women or men think about sex.

Andersen and Cyranowski do, as it happens, report some other research that actually measured the frequency of sexual thoughts among women and men -- with results totally at variance with Brizendine's assertions:

Data comparing the frequency of internally generated thoughts (fantasies) and externally prompted thoughts (sexual urges) among young heterosexual men and women indicate that men report a greater frequency of urges than do women (4.5/day vs. 2.0/day), although the frequency of fantasies were similar (2.5/day; Jones & Barlow, 1990).

That reference is Jones, J. C., & Barlow, D. H. (1990). "Self-reported frequency of sexual urges, fantasies, and masturbatory fantasies in heterosexual males and females." Archives of Sexual Behavior, 19, 269-279. (According to its PsycInfo abstract, this study involved "49 male and 47 female heterosexual undergraduates" -- probably one introductory psychology course -- who "self-monitored the frequency of fantasies, urges, and masturbatory fantasies for 7 consecutive days". And "urges" are "externally provoked sexual throughts", while "fantasies" are "internally generated sexual thoughts".)

Hmm. Adding up this study's tally of undergraduate male sexual thoughts, we get 4.5 male urges + 2.5 male fantasies per day on average, for a total of 7 sexual thoughts, or one every (24*60*60/7 =) 12,342 seconds. Compare Dr. Brizendine's figures: "85 percent of twenty- to thirty-year-old males think about sex every fifty-two seconds". That's more than 237 times hornier -- even if the other 15 percent never thought about sex at all, the average frequency would still be at least two orders of magnitude greater than Jones & Barlow report. (And they sampled male undergraduate psychology students, who must surely be near their life maximum of sexual consciousness.)

How about the female numbers? Jones and Barlow's student diaries yielded 2 female urges + 2.5 female fantasies per day on average, for a total of 4.5 sexual thoughts per day. That's 450% greater than the "once a day" that Brizendine cites in the book's text, and 900% greater than the "once every couple of days" rate in the jacket blurb. Not that the average self-reports from the "47 female undergraduates" in Jones and Barlow's 1990 American sample should be taken to stand for the nature of all women in all times and places -- but this is still 47 more women than we've been able to connect with Brizendine's estimates, at least so far.

Note also that the Jones and Barlow numbers for women amount to one sexual thought every (24*60*60/4.5 =) 19,200 seconds. But you're not going to sell any books by writing that "Men think about sex every 12,300 seconds, while women only have a sexual thought every 19,200 seconds".

OK, so where did Dr. Brizendine get her numbers? Not from the references that she cites, that's for sure. If you can find the source, please tell me.