Endocrine and aggressive responses to competition are moderated by contest outcome, gender, individual versus team competition, and implicit motives

Abstract

This study examined hormonal responses to competition in relation to gender, social context, and implicit motives. Participants (N = 326) were randomly assigned to win or lose in a 10-round, virtual face-to-face competition, in same-sex individual- and team-competition contexts. Saliva samples, taken before and twice after the competition, were assayed for testosterone (T), estradiol (E), progesterone (P), and cortisol (C). Implicit needs for power (nPower) and affiliation (nAffiliation) were assessed with a picture-story exercise before the competition. Aggression was measured via the volume at which participants set noise blasts for their opponents. Men competing individually and women competing as teams showed similar T increases after winning. C was differentially associated with outcome in the team matches, with higher post-match cortisol for winning women, and an opposite effect for male teams. Analyses including implicit motives indicated that situational variables interacted with motivational needs in shaping hormonal responses to competition: in naturally cycling women, nPower predicted T increases after winning and T and E decreases after losing. In men, nPower predicted T increases after losing and decreases after winning. In male teams, nPower predicted C increases after losing, but not after winning, whereas in individual competitions, nPower was a general negative predictor of C changes in women. nAffiliation predicted P increases for women competing as teams, and P decreases for women competing individually. Aggression was higher in men, losers, and teams than in women, winners, and individuals. High aggression was associated with high baseline C in women competing individually and with low baseline C and C decreases in women competing as teams and in men generally. Our findings suggest that while situational and gender factors play a role in hormonal responses to competition, they also depend on their interplay with motivational factors. They also suggest that while aggression is strongly affected by situational factors in the context of a competition, it has no direct association with motivational and hormonal correlates of dominance (nPower, T, E) and instead is associated with (mostly) low levels of C.

Fig 1. Contest outcome effect on changes in hedonic tone, immediately post-contest (T2) and holding hedonic tone at T1 constant, plotted separately for all 4 subsamples.

Fig 2. Illustration of Condition x Outcome x Group interaction.

Post-contest testosterone (averaged across square-root-transformed T2 and T3 values and residualized within each group for square-root-transformed T1 values) are presented on the Y axis.

Fig 3. Illustration of nPower x Outcome x Group interaction.

Post-contest testosterone (averaged across square-root transformed T2 and T3 values and residualized within each group for square-root transformed T1 values) are presented on the Y axis. Lines (blue = winners, red = losers) represent regression slopes.

Fig 4. Illustration of nPower x Outcome x Group interaction.

Post-contest estradiol (averaged across log-transformed T2 and T3 values and residualized within each group for log-transformed T1 values) are presented on the Y axis. Lines (blue = winners, red = losers) represent regression slopes.

Fig 5. Illustration of Condition x Gender x nAffiliation x Time effect, with the data of 4 outliers removed.

Y-axis values represent slopes from T2 to T3, with positive values indicating and increase and negative values a decrease from 0 to 20 min post-contest.

Fig 6. Illustration of Condition x Outcome x Gender effect.

Post-contest cortisol (averaged across log-transformed T2 and T3 values and residualized for log-transformed T1 values) are presented on the Y axis.

Fig 7. Illustration of nPower x Condition x Outcome x Gender effect.

Y axis shows post-contest cortisol (averaged across log-transformed T2 and T3 values and residualized for log-transformed T1 values).

Fig 8. Illustration of Outcome x Gender x round effect, which was significant in single-competition participants, but not in team-competition participants (here, only the Outcome x round effect was significant).

Asterisks denote significant (p < .05) differences between winners and losers on a given round.