47 research outputs found
Testosterone and aggression
In this chapter we have shown that the role of testosterone in modulation of aggression and related behavior is more complex than the simple cause and effect model originally derived from selective animal studies. A broader evolutionarily-based theory (the âChallenge Hypothesisâ) provided the basis for considering research that now dates back over 40 years, ranging from the initial correlational studies, to recent studies that involve sophisticated manipulation of testosterone levels, laboratory procedures rooted in experimental social psychology, and brain imaging. Taken together the emerging evidence shows that competitive behavior influences testosterone levels, which in turn influence aggressive behavior, in a complex way that is moderated by individual differences in personality
In your face: facial metrics predict aggressive behaviour in the laboratory and in varsity and professional hockey players
Facial characteristics are an important basis for judgements about gender, emotion, personality, motivational states and behavioural dispositions. Based on a recent finding of a sexual dimorphism in facial metrics that is independent of body size, we conducted three studies to examine the extent to which individual differences in the facial width-to-height ratio were associated with trait dominance (using a questionnaire) and aggression during a behavioural task and in a naturalistic setting (varsity and professional ice hockey). In study 1, men had a larger facial width-to-height ratio, higher scores of trait dominance, and were more reactively aggressive compared with women. Individual differences in the facial width-to-height ratio predicted reactive aggression in men, but not in women (predicted 15% of variance). In studies 2 (male varsity hockey players) and 3 (male professional hockey players), individual differences in the facial width-to-height ratio were positively related to aggressive behaviour as measured by the number of penalty minutes per game obtained over a season (predicted 29 and 9% of the variance, respectively). Together, these findings suggest that the sexually dimorphic facial width-to-height ratio may be an âhonest signalâ of propensity for aggressive behaviour
Social neuroendocrinology of competition
The relationship between testosterone concentrations and aggressive behaviour in studies
of people has produced very inconsistent findings. However, one consistent fmding that
has emerged is that competitive and aggressive interactions potentiate testosterone release
in both human and non-human species. It has been argued that socially-induced
alterations in testosterone concentrations may function to influence ongoing and/or future
social behaviour. Nonetheless, few studies have empirically tested this hypothesis. The
current series of experiments was designed to address the extent to which competitioninduced fluctuations in testosterone concentrations were associated with ongoing and/or
subsequent social behaviour. In Study 1, men (n = 38) provided saliva samples prior to,
and at the conclusion of, the Point Subtraction Aggression Paradigm (PSAP). Although
baseline testosterone concentrations were not related to aggressive behaviour, there was a
positive correlation between change in testosterone and aggressive behaviour such that
men who were most aggressive on the PSAP demonstrated the largest increase in
testosterone concentrations. Furthermore, a rise in testosterone during the PSAP predicted
willingness to choose a subsequent competitive task. In Study 2, men and women
provided saliva samples prior to and after competing against a same-sex opponent on the
Number Tracing Task (NTT). The outcome of the competition was rigged such that half
of the individuals won most of the races, while the other half lost most of the races, thus
experimentally creating a winner and loser in the laboratory. Following the competitive
interaction, men and women played the PSAP with their same-sex partner. Results
indicated that men selected the aggressive response (but not reward or protection
responses), more frequently than women. For men assigned to the loss condition, an increase in testosterone concentrations in response to the NTT predicted subsequent
aggressive behaviour. For men assigned to the win condition, an increase in testosterone
concentrations in response to the NTT predicted subsequent aggressive behaviour, but
only among those men who scored high on trait dominance. Change in testosterone and
trait dominance did not predict aggressive behaviour in women. In Study 3, men provided
saliva samples prior to, during, and at the end of the PSAP. They were randomly assigned
to one of four experimental conditions that differed in the extent to which they were
provoked and whether they received reward for behaving aggressively (i.e., stealing
points). Results indicated that baseline testosterone concentrations did not correlate with
aggression in any of the experimental conditions. Consistent with Study 1, there was a
positive correlation between change in testosterone and aggressive behaviour among men
who were provoked, but did not receive reward for aggression (i.e., reactive condition).
Men who were provoked but did not receive reward for aggression enjoyed the task the
most and were more likely to choose the competitive versus non-competitive task relative
to men assigned to the other experimental conditions. Also, individual differences in
aggressive behaviour among these men were positively correlated with the extent to
which they enjoyed the task. Together, these studies indicate that testosterone dynamics
within the context of competition influence subsequent competitive and aggressive
behaviours in humans and that testosterone may be a marker of the intrinsically rewarding
nature of costly aggressive behaviour
Cumulative stress in childhood is associated with blunted reward-related brain activity in adulthood
Early life stress (ELS) is strongly associated with negative outcomes in adulthood, including reduced motivation and increased negative mood. The mechanisms mediating these relations, however, are poorly understood. We examined the relation between exposure to ELS and reward-related brain activity, which is known to predict motivation and mood, at age 26, in a sample followed since kindergarten with annual assessments. Using functional neuroimaging, we assayed individual differences in the activity of the ventral striatum (VS) during the processing of monetary rewards associated with a simple card-guessing task, in a sample of 72 male participants. We examined associations between a cumulative measure of ELS exposure and VS activity in adulthood. We found that greater levels of cumulative stress during childhood and adolescence predicted lower reward-related VS activity in adulthood. Extending this general developmental pattern, we found that exposure to stress early in development (between kindergarten and grade 3) was significantly associated with variability in adult VS activity. Our results provide an important demonstration that cumulative life stress, especially during this childhood period, is associated with blunted reward-related VS activity in adulthood. These differences suggest neurobiological pathways through which a history of ELS may contribute to reduced motivation and increased negative mood
Facing Aggression: Cues Differ for Female versus Male Faces
The facial width-to-height ratio (face ratio), is a sexually dimorphic metric associated with actual aggression in men and with
observersâ judgements of aggression in male faces. Here, we sought to determine if observersâ judgements of aggression
were associated with the face ratio in female faces. In three studies, participants rated photographs of female and male
faces on aggression, femininity, masculinity, attractiveness, and nurturing. In Studies 1 and 2, for female and male faces,
judgements of aggression were associated with the face ratio even when other cues in the face related to masculinity were
controlled statistically. Nevertheless, correlations between the face ratio and judgements of aggression were smaller for
female than for male faces (F1,36 = 7.43, p = 0.01). In Study 1, there was no significant relationship between judgements of
femininity and of aggression in female faces. In Study 2, the association between judgements of masculinity and aggression
was weaker in female faces than for male faces in Study 1. The weaker association in female faces may be because
aggression and masculinity are stereotypically male traits. Thus, in Study 3, observers rated faces on nurturing (a
stereotypically female trait) and on femininity. Judgements of nurturing were associated with femininity (positively) and
masculinity (negatively) ratings in both female and male faces. In summary, the perception of aggression differs in female
versus male faces. The sex difference was not simply because aggression is a gendered construct; the relationships between
masculinity/femininity and nurturing were similar for male and female faces even though nurturing is also a gendered
construct. Masculinity and femininity ratings are not associated with aggression ratings nor with the face ratio for female
faces. In contrast, all four variables are highly inter-correlated in male faces, likely because these cues in male faces serve as
ââhonest signalsââ
Facing Aggression: Cues Differ for Female versus Male Faces
The facial width-to-height ratio (face ratio), is a sexually dimorphic metric associated with actual aggression in men and with observers' judgements of aggression in male faces. Here, we sought to determine if observers' judgements of aggression were associated with the face ratio in female faces. In three studies, participants rated photographs of female and male faces on aggression, femininity, masculinity, attractiveness, and nurturing. In Studies 1 and 2, for female and male faces, judgements of aggression were associated with the face ratio even when other cues in the face related to masculinity were controlled statistically. Nevertheless, correlations between the face ratio and judgements of aggression were smaller for female than for male faces (F1,36â=â7.43, pâ=â0.01). In Study 1, there was no significant relationship between judgements of femininity and of aggression in female faces. In Study 2, the association between judgements of masculinity and aggression was weaker in female faces than for male faces in Study 1. The weaker association in female faces may be because aggression and masculinity are stereotypically male traits. Thus, in Study 3, observers rated faces on nurturing (a stereotypically female trait) and on femininity. Judgements of nurturing were associated with femininity (positively) and masculinity (negatively) ratings in both female and male faces. In summary, the perception of aggression differs in female versus male faces. The sex difference was not simply because aggression is a gendered construct; the relationships between masculinity/femininity and nurturing were similar for male and female faces even though nurturing is also a gendered construct. Masculinity and femininity ratings are not associated with aggression ratings nor with the face ratio for female faces. In contrast, all four variables are highly inter-correlated in male faces, likely because these cues in male faces serve as âhonest signalsâ
Salivary testosterone and cortisol : role of athletic setting, game outcome, and game location /
Many studies investigating the relationship between hormones and
competition have focused on athletic competition. The athletic setting enables
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researchers to investigate the hormone-behaviour relationship in a relatively
controlled environment. However, research to date has been based on observations
made from single status contests and/or weekend tournaments and as such, does not
provide a clear picture of an individual's average hormonal responses to both victory
and defeat.
In appreciation of this limitation, the current study tracked elite hockey
players throughout a hockey season, measuring pre- and post-game salivary
testosterone and Cortisol as well as psychological measures. I was interested in
determining whether status outcome (win vs. loss) would influence an individual's
testosterone and Cortisol responses to competition. Furthermore, I was also interested
in assessing whether testosterone and Cortisol responses were specific to the
competitive environment or whether similar hormonal responses would occur during
non-competitive practice sessions. Last, I was interested in whether there were any
differences in pre-game hormonal and psychological states depending on where the
status contest was held: home versus away.
The results indicated that game outcome moderated the testosterone responses
to competition. That is, testosterone increased significantly more after a victory
compared to a defeat. Furthermore, a loss of status produced significantly hreports, the players did not show an anticipatory rise in either Cortisol or testosterone
prior to competition.
In addition to the effects of status outcome on hormonal levels, it was also
found that these hormonal responses were specific to competition. The athletes in the
current study did not demonstrate any hormonal responses to the practice sessions.
Last, there were significant differences in pre-game testosterone as well as in selfconfidence,
cognitive, and somatic anxiety levels depending on the location at which
the status contest took place. Pre-game testosterone and self-confidence levels were
significantly higher prior to games played in the home venue. In contrast, pre-game
somatic and cognitive anxiety levels were significantly higher prior to games played
in the away venue.
The current findings add to the developing literature on the relationship
between hormones and competition. This was the first study to detect a moderating
effect of status outcome on testosterone responses in a team sport. Furthermore, this
was also the first study in humans to demonstrate that post-contest Cortisol levels
were significantly higher after a loss of status. Last, the current study also adds to the
sport psychology literature by demonstrating that pre-game psychological variables
differ depending on where the status contest is being held: higher self-confidence at
home and higher somatic and cognitive anxiety away. Taken together, the results
from the current thesis may have important practical relevance to coaches, trainers
and sport psychologists who are always trying to find ways to maximize performance.
post-game Cortisol levels than did an increase in status. In contrast to previou