Hormones
Chemical messengers released by glands in the endocrine system, a network of glands and organs that regulate various bodily functions by secreting hormones directly into the bloodstream.
Unlike neurotransmitters, which act rapidly within the nervous system, hormones travel through the bloodstream and regulate slower processes, such as growth and metabolism.
Testosterone and Aggression
Testosterone, a steroid hormone primarily produced in the testes (males) and ovaries (females), is often linked to behaviors such as aggression, dominance, and competitiveness.
NoteMales generally have higher levels of testosterone than females, which may partly explain differences in aggressive tendencies between the sexes.
Key Studies
Castration and Aggression in Rats
Case studyAlbert et al., 1986
Aim: To investigate the causal relationship between testosterone levels and aggression in alpha male rats.
Method: Experimental; testosterone levels were manipulated through castration and subsequent hormone replacement.
Procedure: Alpha male rats were identified and divided into groups. Some were castrated, while others remained intact. For the castrated group, testosterone was later replaced to observe behavioral changes.
Results: Castrated rats showed reduced aggression toward other rats. When testosterone was reintroduced, aggression levels returned to baseline.
Conclusion: Testosterone directly influences aggressive behavior, establishing a cause-and-effect relationship in animal models.
Testosterone Levels and Aggression
Case studyEhrenkranz et al., 1974
Aim: To explore the correlation between testosterone levels and aggression in human males.
Method: Observational study comparing testosterone levels across three groups of prisoners.
Procedure: Participants were categorized into three groups: violent and aggressive, socially dominant, and non-aggressive/non-dominant. Their testosterone levels were measured and compared.
Results: Higher testosterone levels were found in the violent/aggressive and socially dominant groups compared to the non-aggressive group.
Conclusion: Testosterone may be linked to aggressive behavior and social dominance in humans.
Case studyCarré et al. (2016):
Aim: Whether certain personality traits affect aggressive responses to a game.
Sample: 121 males.
Method: Participants were randomly assigned to two groups: one received a testosterone injection, while the other received a placebo, using a double-blind technique. They then participated in a decision-making game designed to assess aggression after being provoked by their computer-based partner. Personality traits were assessed through a questionnaire.
Results: Increased testosterone alone did not provoke aggression. Only participants who received an additional dose and scored high in aggression but low in impulse control exhibited higher aggression.
Conclusion: There may be other factors that work with testosterone to influence aggressive behaviour, and testosterone alone may not be a strong enough influence.
Oxytocin and Social Behavior
Oxytocin, often referred to as the "love hormone" or "bonding chemical", is released by the pituitary gland, a small, pea-shaped gland located at the base of the brain that regulates vital hormonal functions in the body. Oxytocin plays a significant role in social bonding, trust, and reproductive behaviors.
Case studyScheele et al., 2012
Aim: To explore how oxytocin influences fidelity in heterosexual males.
Method: Double-blind, independent measures experiment.
Procedure: Participants received either oxytocin or a placebo intranasally. They participated in two tasks:
- Stop-distance paradigm: Participants approached an attractive female confederate and stopped at a point of discomfort.
- Approach/avoidance task: Participants responded to images (e.g., attractive women, landscapes) using a joystick to indicate approach or avoidance tendencies.
Results: Oxytocin caused men in relationships to maintain a greater physical distance from attractive women, while single men showed no such effect. The hormone also selectively influenced reactions to images of attractive women.
Conclusion: Oxytocin promotes fidelity by modulating social behaviors, particularly in pair-bonded males.
Case studyFerguson et al., 2000
Aim: To examine the role of oxytocin in social recognition and memory.
Method: Experimental; oxytocin gene knockout technique used in mice.
Procedure: Male mice were exposed to a female mouse over four habituation trials, followed by a fifth trial introducing a new female mouse. Olfactory investigation time was recorded.
Results: Normal mice showed reduced investigation time across habituation trials and increased attention to the new mouse. Oxytocin-deficient mice did not show this pattern, failing to distinguish between familiar and unfamiliar mice.
Conclusion: Oxytocin is critical for developing social memory, highlighting its potential role in disorders like autism.
