Abstract: According to sexual selection theory, intra-sex competition mainly among males leads to male characteristics known as weapons. The large body size and thick proboscis of male elephant seals and the robust horns and antlers of various ungulate stags are well-known examples of weapons. Inter-sex selection or mate choice, mostly exercised by the limiting sex or females, leads male characteristics known as ornaments. The vibrant colors of the guppy and the bright plumage of various birds are examples of ornaments. Whereas human males possess similar physical sex-dimorphic characteristics such as larger body frames (weapons), and lower voice pitch (ornaments), human sex-dimorphism is mainly shown as weapon-like (e.g., aggression) and ornament-like behavior (e.g., bragging). Human risk taking is such an ornament-like behavior because, like all ornaments which are functionally useless but are yet costly to sustain, risk taking behavior brings danger to its carriers without apparent functional purposes. Like ornaments, risk taking behavior is preferred by conspecific females who find its male carriers sexually attractive. The purpose of the present study was to test sexual selection theory on humans by investigating the association between risk-taking behavior and mating motives among men but not women. This hypothesis was tested against the rival hypothesis that risk taking may be externally motivated by monetary reward that renders similar effects on both men and women.
These hypotheses were tested on a sample of 127 graduate students (62 males, mean age = 21.47; SD = 1.59). In a between-group design, participants were exposed, on a computer screen, either to attractive opposite-sex pictures (the mating condition) or pictures of money or medals (the control or monetary reward condition). These two conditions were manipulated as a simple perceptual task where participants were instructed to decide on the location of each picture as it flashes on the screen (500 ms) by pressing one of two keys on the keyboard. This is to distract the participants from being aware of the intended experimental manipulation (mating versus monetary reward). To facilitate this distraction, attractive opposite sex pictures were also mixed with a small number of average-looking opposite sex pictures, and the monetary award pictures were mixed with a small number of non-reward scenes. After the picture exposure, each participant was given 19 different risk taking scenarios and was asked to assess the likelihood the participant would engage in each of the risk-taking behavior. The 19 risk-taking scenarios represent four domains of risk, including financial, health, social, and recreational risk. Composite scores representing the four domains were used as the dependent variables.
Except for one of the four dependent variables, A 2 (mating vs. reward) × 2 (gender of the participants) ANOVA did not yield a significant interaction effect. However, separate t-tests were statistically significant, showing that men indicated higher likelihood to take risk after being exposed to attractive opposite-sex pictures than to reward pictures, whereas women did not show the difference in risk taking likelihood assessment besides social risk. Taking health risk for example, M = 21.03 vs. 18.67 under the mating vs. reward condition for men. The mean difference was statistically significant, p<.01. For women, M = 17.94 and 17.35, respectively. Other mean comparisons showed similar results which are reported in Table 1 in the main text. The results support sexual selection theory. Like most mammals, human males but not females have acquired ornament-like behaviors which are driven by mating motives. When attractive women are around, men are more likely to engage in functionally useless and potentially harmful behavior, which, however, are “useful” in the sense that they serve as signals of good genes. Thus, men’s risk taking is driven by mating motives. Women are drawn to men’s risk taking behavior for the same sexual selection reason, i.e., women use the signals to select quality mates. In part to address reviewers’ concerns, motives and need states serve as proximate cues that drive our behavior both consciously and unconsciously. In everyday life, mating motives, like many other motives, may remain unconscious most of the time which nonetheless drive and shape our behavior as is shown by the present study.

Key words: mating motives, sexual selection, risk taking, gender