1 Introduction Humans exhibit seasonal variation in different physiological and behavioural processes (see review in Bronson 2004; Kimura and Hampson 1994). Mood fluctuations over the year, particularly at higher latitudes, have also been shown by many authors (for review see Harmatz et al 2000). For instance, seasonal affective disorder is a depressive disorder that occurs during the winter (Dalgleish et al 1996), but mood and behaviour also vary seasonally in healthy individuals (eg Kasper et al 1989; Lacoste and Wirz- Justice 1987; Terman 1988). Such variation might be important because hormones, neurotransmitters, and/or mood fluctuations over the year may cause seasonal fluctu- ations in fertility (Lam and Miron 1994) or sexual behaviour (Smolensky et al 1981). It is also known that human taste perception in patients with seasonal affective dis- order may change over the year (Arbisi et al 1996). Therefore it is possible that visual perception and judgments of the attractiveness of others or self-attractiveness could also differ in relation to the season of the year. Circannual changes in mood might influence either perception of self-attractiveness or attractiveness of others (including sexual partners). It is also well-known that individuals adjust their judgment of the attractiveness of others according to whether the target person is presented in a set of attractive or unattractive stimuli (Geiselman et al 1984; Kenrick et al 1989, 1994; Kowner and Ogawa 1993). People also judge their self-attractiveness in relation to the attractiveness of the stimuli (Thornton and Maurice 1997). In other words, when people are exposed to attractive stimuli (faces or bodies) they usually assess their self-attractiveness and attractiveness of other target images lower than when they are exposed to unattractive stimuli. This phenomenon is called the `contrast effect'. If then in different seasons of the year people are exposed in real life to different bodies (or parts of bodies), they can assess the same bodystimuli in the two seasons differently. Men's attraction to women's bodies changes seasonally Perception, 2008, volume 37, pages 1079 ^ 1085 Bogusaw Pawlowskiô Department of Anthropology, University of Wrocaw, ul. Kuz¨ nicza 35, Wrocaw 50-138, Poland; e-mail: boguslaw.pawlowski@antro.pan.wroc.pl (ô also Departamento de Ecologia Humana, CINVESTAV-Me¨ rida, Unidad Me¨ rida Km, 6 Antigua carretera a Progreso, Apdo. Postal 73, Cordemex, 97310, Me¨ rida, Yuc, Me¨ xico; and Institute of Anthropology, Polish Academy of Sciences, ul. Kuz¨ nicza 35, Wrocaw 50-951, Poland) Piotr Sorokowski Institute of Psychology, University of Wrocaw, ul. J. Dawida 1, 50-527 Wrocaw, Poland; e-mail: piotrsorokowski@yahoo.co.uk Received 31 October 2006, in revised form 9 November 2007 Abstract. Humans exhibit seasonal variation in hormone levels, behaviour, and perception. Here we show that men's assessments of women's attractiveness change also seasonally. In five seasons (from winter 2004 to winter 2005) 114 heterosexual men were asked to assess the attractiveness of the same stimuli: photos of a female with three different waist-to-hip ratios; photos of female breasts, and photos of average-looking faces of young women. For each season, the scores given to the stimuli of the same category (body shape, breast, and face) were combined. Friedman's test revealed significant changes for body shape and breast attractiveness assessments across the seasons, but no changes for face ratings. The highest scores for attractiveness were given in winter and the lowest in summer. We suggest that the observed seasonality is related to the well- known `contrast effect'. More frequent exposure to women's bodies in warmer seasons might increase men's attractiveness criteria for women's body shape and breasts. doi:10.1068/p5715