Abstract:

Throughout the animal kingdom, larger animals are more likely to attain dominance and thus enhance their ability to acquire mates. In human males, body height is also associated with the success and failure in sexual selection. For example, studies have found that taller men have higher strength or fighting ability, are more likely to have higher overall income and higher social status, and hold greater potential for acquiring mates. However, shorter men are not necessarily doomed with disadvantages. Previous studies have suggested that men have a flexible status psychology that may allow them to exercise behavioral flexibility (e.g., by showing more indirect aggression or feeling more jealousy toward sexual rivals) to compensate for their disadvantage in height. Given the importance of risk-taking behavior in signalizing the quality of ones’ genes, in the present study, we hypothesized that when encountering a taller same-sex rival, shorter men would compensate for their disadvantages in height by showing more risk-taking behavior, and their mating motives would modulate such an effect.
This hypothesis was tested by four behavioral studies. We measured risk-taking behavior by employing a well-validated and computerized laboratory task (i.e., Balloon Analogue Risk-Taking Task, BART). In Studies 1 and 2, male or female participants (176 participants in Study 1, and 246 participants in Study 2, respectively) were paired with taller or shorter same-sex opponents, and were asked to compete with their opponents in a computerized game (i.e., the BART task). In Study 3 (255 male participants), we further tested our hypothesis by situationally activating the mating motives of male participants (i.e., by watching videos depicting highly attractive females) and paired them with taller or shorter male opponents in the BART task as in Studies 1 and 2. In Study 4 (90 male participants), we further investigated the effects of chronic mating motive and the relative height disadvantage on men's risk-taking by employing the Mate Seeking scale of Fundamental Social Motives Inventory.
The results showed that: 1) male participants had significantly higher BART scores (i.e., the average numbers of pumps per unexploded balloon) when their opponents were taller; 2) such an effect was caused by the increase in risk-taking propensity when facing a taller opponent; facing a shorter opponent didn’t affect the risk-taking of male participants (also be compared to a no-height-info control); 3) the relative height difference between participants and their opponents did not affect the risk-taking of female participants; 4) situationally activating the mating motives of male participants significantly affected the effects of relative height disadvantage on male risk-taking; after watching the mating prime, male participants were more likely to elevate their risk-propensity to compensate for their disadvantage in height; 5) male participants with higher level of chronic mating motivation were also more likely to elevate their risk-propensity to compensate for the height disadvantage.
The above results support our hypothesis, suggesting that men may have evolved a behavioral strategy to elevate their risk-taking propensity to compensate for their height disadvantage, and this strategy is driven by motives of intrasexual competition and mating. Our study thus provides further evidence for the evolutionary theory of Napoleon complex.

Key words: Napoleon complex, sexual selection, risk-taking, height, mating motive