This research explores whether male risk taking emerges as a sexual display strategy in the presence of attractive women. Experiments 1 to 3 explored whether young males reported and engaged in more risk taking after viewing pictures of highly attractive females. Possible self-control mechanisms were investigated via working memory, reversal learning, and Stroop tasks. In addition, second to fourth digit ratio (2D:4D) was measured as a proxy for individual differences in testosterone. Viewing pictures of highly attractive females led to greater self-reported risk-taking. 2D:4D was found to moderate the effect on risk-taking behaviours, with increases for high, but decreases for low testosterone males. Digit ratio also moderated the effects observed on the Stroop and reversal learning tasks. Experiments 4 and 5 extended these findings to examine how power interacts with testosterone to influence risk taking and inhibitory control. As testosterone is as-sociated with the pursuit of power and status (Dabbs & Dabbs, 2000), high testoster-one individuals primed with power were expected to have little reason to disrupt the status quo and thus should be risk-avoidant. Conversely, high-testosterone individuals primed with low power were expected to use risk taking as a vehicle for pursuing po-tential gains to their status and resources. The findings from two experiments are con-sistent with these predictions. In Experiment 1, higher testosterone males (as indicated by second–fourth digit ratio) showed greater risk-taking when primed with low power. Experiment 2 replicated this effect and also showed that when primed with high power, higher testosterone males took fewer risks. The influence of power on Stroop performance was also moderated by individual differences in testosterone. Par-ticipants primed with high power showed better Stroop performance if they were lower in testosterone, whereas participants primed with low power showed better Stroop performance if they were higher in testosterone. These results suggest that greater executive control accompanies but does not underlie enhanced risk taking, caused by testosterone and power. Finally, results from a field experiment (Experiment 6) with skateboarders demon-strate that physical risk taking by young male skateboarders increases in the presence of an attractive female. This increased risk taking led to more successes but also more crash landings in front of the female observer. Mediational analyses suggest that this increase in risk taking is caused in part by elevated testosterone levels of men who performed in front of the attractive female. In addition, skateboarders’ risk taking was predicted by their performance on a reversal-learning task, reversal-learning perform-ance was disrupted by the presence of the attractive female, and the female’s presence moderated the observed relationship between risk taking and reversal learning. These results suggest that men use physical risk taking as a sexual display strategy, and they provide suggestive evidence regarding possible hormonal and neural mechanisms.

This research explores whether male risk taking emerges as a sexual display strategy in the presence of attractive women. Experiments 1 to 3 explored whether young males reported and engaged in more risk taking after viewing pictures of highly attractive females. Possible self-control mechanisms were investigated via working memory, reversal learning, and Stroop tasks. In addition, second to fourth digit ratio (2D:4D) was measured as a proxy for individual differences in testosterone. Viewing pictures of highly attractive females led to greater self-reported risk-taking. 2D:4D was found to moderate the effect on risk-taking behaviours, with increases for high, but decreases for low testosterone males. Digit ratio also moderated the effects observed on the Stroop and reversal learning tasks. Experiments 4 and 5 extended these findings to examine how power interacts with testosterone to influence risk taking and inhibitory control. As testosterone is as-sociated with the pursuit of power and status (Dabbs & Dabbs, 2000), high testoster-one individuals primed with power were expected to have little reason to disrupt the status quo and thus should be risk-avoidant. Conversely, high-testosterone individuals primed with low power were expected to use risk taking as a vehicle for pursuing po-tential gains to their status and resources. The findings from two experiments are con-sistent with these predictions. In Experiment 1, higher testosterone males (as indicated by second–fourth digit ratio) showed greater risk-taking when primed with low power. Experiment 2 replicated this effect and also showed that when primed with high power, higher testosterone males took fewer risks. The influence of power on Stroop performance was also moderated by individual differences in testosterone. Par-ticipants primed with high power showed better Stroop performance if they were lower in testosterone, whereas participants primed with low power showed better Stroop performance if they were higher in testosterone. These results suggest that greater executive control accompanies but does not underlie enhanced risk taking, caused by testosterone and power. Finally, results from a field experiment (Experiment 6) with skateboarders demon-strate that physical risk taking by young male skateboarders increases in the presence of an attractive female. This increased risk taking led to more successes but also more crash landings in front of the female observer. Mediational analyses suggest that this increase in risk taking is caused in part by elevated testosterone levels of men who performed in front of the attractive female. In addition, skateboarders’ risk taking was predicted by their performance on a reversal-learning task, reversal-learning perform-ance was disrupted by the presence of the attractive female, and the female’s presence moderated the observed relationship between risk taking and reversal learning. These results suggest that men use physical risk taking as a sexual display strategy, and they provide suggestive evidence regarding possible hormonal and neural mechanisms.

This research explores whether male risk taking emerges as a sexual display strategy in the presence of attractive women. Experiments 1 to 3 explored whether young males reported and engaged in more risk taking after viewing pictures of highly attractive females. Possible self-control mechanisms were investigated via working memory, reversal learning, and Stroop tasks. In addition, second to fourth digit ratio (2D:4D) was measured as a proxy for individual differences in testosterone. Viewing pictures of highly attractive females led to greater self-reported risk-taking. 2D:4D was found to moderate the effect on risk-taking behaviours, with increases for high, but decreases for low testosterone males. Digit ratio also moderated the effects observed on the Stroop and reversal learning tasks. Experiments 4 and 5 extended these findings to examine how power interacts with testosterone to influence risk taking and inhibitory control. As testosterone is as-sociated with the pursuit of power and status (Dabbs & Dabbs, 2000), high testoster-one individuals primed with power were expected to have little reason to disrupt the status quo and thus should be risk-avoidant. Conversely, high-testosterone individuals primed with low power were expected to use risk taking as a vehicle for pursuing po-tential gains to their status and resources. The findings from two experiments are con-sistent with these predictions. In Experiment 1, higher testosterone males (as indicated by second–fourth digit ratio) showed greater risk-taking when primed with low power. Experiment 2 replicated this effect and also showed that when primed with high power, higher testosterone males took fewer risks. The influence of power on Stroop performance was also moderated by individual differences in testosterone. Par-ticipants primed with high power showed better Stroop performance if they were lower in testosterone, whereas participants primed with low power showed better Stroop performance if they were higher in testosterone. These results suggest that greater executive control accompanies but does not underlie enhanced risk taking, caused by testosterone and power. Finally, results from a field experiment (Experiment 6) with skateboarders demon-strate that physical risk taking by young male skateboarders increases in the presence of an attractive female. This increased risk taking led to more successes but also more crash landings in front of the female observer. Mediational analyses suggest that this increase in risk taking is caused in part by elevated testosterone levels of men who performed in front of the attractive female. In addition, skateboarders’ risk taking was predicted by their performance on a reversal-learning task, reversal-learning perform-ance was disrupted by the presence of the attractive female, and the female’s presence moderated the observed relationship between risk taking and reversal learning. These results suggest that men use physical risk taking as a sexual display strategy, and they provide suggestive evidence regarding possible hormonal and neural mechanisms.

There is often an assumption that there is a right and a wrong way for consumers to behave. For example, with regard to eating, people should make food choices based on maximizing vitamins and minerals and not consuming more calories than one expends in a day. Likewise, it is assumed that buying products to conspicuously signal a message to another is wasteful and maladaptive. The research in this thesis challenges these assumptions and argues that these behaviours can be both adaptive and maladaptive depending on one’s environmental conditions. In this thesis, I describe three experiments that examine how perception of environmental harshness affects appetite for different types of foods. The data shows that food desirability in adulthood varies depending on early childhood socio-economic status, the type of environmental stressor (harsh social, harsh economic and harsh physical safety) and the intensity of the stressors within each of these environments. It was also found that different types of environmental harshness differentially affects food desire based on energy density and food category type. In addition to the experiments on harshness and food desirability, I have examined how environmental harshness affects desire for products that are used to conspicuously signal information to others. For example, under conditions of environmental stress, products may be used to advertise that a male possesses financial or physical power which is desirable to a potential mate. Likewise, a women may buy products to display she possess financial power or she may purchase products that augment her beauty and sexual attractiveness. These studies reveal that product desire is also affected by different types of environmental harshness and the intensity of the stress generated by these environmental conditions. Through the research described in this thesis, we gain a more comprehensive understanding of the proximate variables that influence two subsets of consumer behaviour, namely food desire and product signalling, and how these behaviours may have been selected for due to their adaptive value.

La fragmentation des habitats ainsi que la réduction de leur disponibilité sont des menaces importantes pour les écosystèmes, notamment aquatiques. La disponibilité et la qualité des sites de fraie du saumon Atlantique peut donc être limitante dans certaines rivières. Après la migration en rivière, les femelles saumon vont chercher à s'établir dans un des sites de fraie disponibles. La distribution spatiale des femelles va alors influer sur la distribution spatiale des mâles reproducteurs qui vont chercher soit à monopoliser plusieurs femelles (pour les mâles dominants), soit à les approcher en adoptant un comportement "furtif" (pour les mâles satellites). L'accès des mâles aux femelles va donc dépendre de la distribution spatiale des femelles et des déplacements des mâles dans la rivière. La distribution des femelles va également jouer sur la distribution spatiale des juvéniles, les concentrant à certains endroits. Cette concentration peut augmenter la mortalité densité-dépendante qui modifie la dynamique de la population. Cette thèse avait pour but d'évaluer comment l'utilisation de l'espace des potentiels reproducteurs, c'est à dire les individus matures, influence la dynamique de la population et la sélection sexuelle.Des séries temporelles de stock (oeufs déposés) et de recrutement (juvéniles) pour la population de saumon de la Nivelle ont été associées à des mesures de l'agrégation spatiale des nids creusés par les femelles. L'effet des déplacements et de la distribution des reproducteurs sur leur participation à la reproduction a notamment été testé via la reconstruction du réseau d'interactions sexuelles dans la Nivelle.J'ai ainsi démontré que l'agrégation spatiale des nids influa sur la variabilité du recrutement mais pas sur le recrutement moyen. Cette agrégation qui résulte de l'agrégation des femelles a également été liée au nombre de reproducteurs ayant engendrés des juvéniles. Le réseau d'interactions sexuelles a permis de mettre en évidence une structure sociale locale au sein de la population. Cette structure et les compétiteurs présents pouvaient par exemple diminuer le succès reproducteur des mâles. Notamment, les tacons matures qui participent à la reproduction avant de migrer en mer renforçaient la compétition sexuelle dont les mâles dominants faisaient l'objet. Enfin, ces mêmes tacons matures adoptèrent des comportements spatiaux du fait de leur statut de maturité avec des individus bougeant peu et des individus se déplaçant vers l'amont. Ces comportements spatiaux influaient leur participation à la reproduction, l'étendue des domaines de vie et les déplacements vers l'amont augmentaient la probabilité de rencontrer une femelle.Mes résultats m'ont permis de mettre en évidence l'effet de l'utilisation de l'espace des potentiels reproducteurs sur la dynamique de la population et sur la sélection sexuelle. Ainsi, en combinant différentes échelles spatiales et temporelles il a été montré que l'agrégation des femelles pouvait être bénéfique pour la dynamique de la population. Il semble que les femelles tendent à s'agréger d'abord sur les meilleurs sites de fraie avec une plus forte stabilité environnementale. Cette distribution des femelles affecta la capacité des mâles à monopoliser plusieurs femelles, une agrégation modérée permettant une monopolisation. La participation des mâles furtifs anadromes ou tacons matures était également dépendante de l'agrégation des femelles. Il apparait que la disponibilité d'habitats adéquats pour la reproduction semble limitante dans la Nivelle et notamment du fait de la présence de barrages. Ce manque semble affecter le système d'appariement de la population et la sélection sexuelle y opérant. Des mesures visant à améliorer la qualité des sites de fraie déjà disponibles ainsi que leur accessibilité pourraient être envisagées. / Habitat fragmentation and reduction in the availability of suitable habitats are significant threats to ecosystems in particularly for freshwater ones. For instance, accessibility, availability, and quality of breeding sites of Atlantic salmon, \textit{Salmo salar}, can be restricting in some rivers due to human activities and dams. Such threats may affect distribution of potential breeders because after their up-river migration, salmon females distribute within available breeding sites. Spatial distribution of females determines the spatial distribution of breeder males. Dominant males try to monopolise several females, whereas subordinate males adopt a sneaky behaviour. Access to females by males depends on the spatial distribution of females and on males' displacements within a river. The spatial distribution of females generates the spatial distribution of juveniles, aggregating them at some breeding sites. The latter aggregation of juveniles may raise the density-dependent mortality with potential consequences on population dynamics. The thesis aims to assess how space use of potential breeders, namely mature individuals able to spawn or fertilise eggs, influence population dynamics and sexual selection.I combined different approaches and different temporal and spatial scales to potential effects of space use of potential breeders. Time series of stock (deposited eggs) and of recruitment (juveniles) for the salmon population of the Nivelle River were combined with measures of spatial aggregation of nests. The effects of displacements and spatial distribution of potential breeders on their participation in reproduction were tested through inferring the sexual network of the population.I found that spatial aggregation of nests improved the recruitment variability but did not affect the average recruitment. The spatial aggregation of nests resulting from female aggregation was also linked to the number of effective breeders through a U-shaped curve. Such relationships suggested mate monopolization dependent on the spatial aggregation of females. The negative effect of the spatial isolation of females on their number of mates also suggest such mate monopolization. Then, the inferred sexual network enabled me to highlight a local social structure within the population. The latter structure and social competitors impacted the reproductive success of anadromous males. The participation of mature parr was one of the factors diminishing the sexual competition faced by anadromous males. Finally, mature parr were more mobile and moved more upstream than immature parr. Spatial behaviours of mature parr were linked to their participation in reproduction, individuals exhibiting wider home ranges had a higher probability to encounter females.Altogether my results show that space use of potential breeders affect both population dynamics and sexual selection. Then, spatial aggregation of females and of their nests can be beneficial for population dynamics as shown by combining different temporal and spatial scales. Females seemed to aggregate within the best breeding sites with a better environmental stability. The spatial distribution of females affected the ability of males to monopolise several females and participation of sneaky males. The availability of suitable good breeding habitats seemed restricting in the Nivelle, potentially due to the presence of impassable upstream dams. The lack of suitable breeding sites seemed impacting the mating system of the population and the sexual selection operating in. Some management actions to improve the quality of breeding sites and their availability could be planned.