The endocrine system: hormones and behaviour Flashcards
What are hormones and what do they affect?
naturally occurring chemicals in the body that affect mood, behaviour and development
Categories of hormones: amino acid derivatives
Involved in the synthesis and transmission of peptides, proteins and neurotransmitters
Categories of hormones: peptides + proteins
chains of amino acids, support growth processes
Categories of hormones: steroids
Role in sexual development
Can penetrate cell membranes to alter genetic traits, so effects can be long-lasting
How are hormones different to neurotransmitters?
hormones can operate over a greater distance than NTs
An example of amino acid derivative
thyroid gland hormone
How do steroids increase muscle mass?
by increasing testosterone
Hormones are produced and released by…
endocrine glands
What is the endocrine system?
Series of cells, glands and organs that produce hormones
Endocrine glands secrete…
hormones directly into bloodstream
Endocrine glands:
pineal body pituitary hypothalamus thyroid adrenal pancreas ovaries/testes
Why are hormones important?
Evidence of hormonal activity can validate biological explanations of behaviour
Hormones and their roles
oxytocin (social bonding) cortison (stress) melatonin (sleep regulation) immunoglobulin A (immune system functioning) testosterone (aggression, competition)
Who discovered hormones and how?
Arnold Berthold (1849) Studied castrated roosters. Unattached testes led to normal roosters. Testes must have released a biochemical substance that affects development + behaviour
How have technological advances made it easier to measure hormones in research?
Saliva (not blood) samples - no training required, inexpensive, non-invasive
Strict but robust protocols (standardised experimental procedures, Human Tissue Act)
Ethical issues surrounding tissue samples
Potential exposure to infectious diseases
Might reveal sensitive info e.g. infertility
Upsetting/embarrassing procedure
Disposing of samples - can’t keep indefinitely
Oxytocin: breast feeding
oxytocin causes the ‘let down reflex’ - makes milk available to baby
- Nipple stimulation from sucking baby
- Brain activity
- Nerve impulses to hypothalamus –> creates oxytocin
- Oxytocin causes mammary gland cells to contract
- This releases milk to baby
Oxytocin: childbirth
oxytocin causes uterine contraction
stimulates cervical dilation before birth
stimulated contractions of uterus during later stages of labour
injections of oxytocin often used to induce or accelerate labour
Oxytocin: post-partum rats
van Leengoed et al. (1987)
mothers with oxytocin antagonist showed no maternal behaviour or attachment to pups
suggests oxytocin plays a role in rapid onset on post-partum maternal behaviour
Oxytocin: prairie voles
Bales + Carter (2003) gave male PVs either oxytocin or control injection
males exposed to oxytocin showed stronger partner preference, more social interaction and contact
suggests oxytocin plays a role in formation of pair bonds
Oxytocin: trust
Kosfeld et al. (2005) double blind study
participants received oxytocin or placebo
compare trusting behaviour in both investors and trustees
participants interacted anonymously and with real money
Findings: investors in oxytocin group offered 17% more (but no effect on trustee behaviour)
Oxytocin: trust - mechanism
possible increase in prosocial approach behaviour by inhibiting defensive behaviours
increased optimism of successful outcome
Oxytocin: touch and giving to strangers
Morhenn et al. (2008)
Participants received Swedish massage or rested for 15 mins
Then played trust game
Massage group returned more as trustees, predicted by their oxytocin levels
Possible mechanism: massage primed Ps to respond to trust signal with increased oxytocin levels
Oxytocin and cooperation
Oxytocin could be the proximate mechanism that leads to cooperation
Shows a biological basis to human cooperation
Theodoridou et al. (2009): Oxytocin leads to increased ratings of…
attractiveness and trustworthiness of strangers
Oxytocin: gaze and facial processing (Guastella et al., 2009)
Oxytocin led to an increased number of fixations and total gaze time toward the eye region
Oxytocin and mind-reading
Oxytocin improved performance on the Reading the Mind in the Eyes Test
Oxytocin and hypnosis
Individuals less susceptible to hypnosis given oxytocin spray
Increased hypnotic responding levels
Due to increased rapport between individual and hypnotist?
Sex hormones are produced by…
the gonads (ovaries and testes) and adrenal gland
2 main types of sex hormones:
androgens (including testosterone and anabolic steroids)
oestrogen (including estradiol)
Although both present in everyone, _______ are viewed as the ‘male’ hormone and _______ as the ‘female’ hormone
androgens
oestrogen
Sex hormones are important in the development of…
sexually distinct traits in humans
Primary characteristics of testosterone
maturation of male genitalia and sperm production
Secondary characteristics of testosterone
facial and genital hair voice change shifts in hairline muscle development redistribution of body fat
There is ____ times more testosterone in males than in females
seven
In females, testosterone is produced in…
adrenal cortex and ovaries
2 measures of testosterone and what they account for
FLUCTUATING - accounts for competition, aggression, dominance
PRENATAL - accounts for physical features e.g. facial structure, digit length, symmetry
Greatest difference in testosterone is between week __ and __ of gestation
8 and 16
Geschwind & Galaburda (1985): foetal testosterone and brain lateralisation
foetal testosterone FACILITATES growth in regions of the RIGHT hemisphere, and INHIBITS growth in the same regions of the LEFT hemisphere.
Foetal testosterone and behaviours: Goy et al. (1988)
Pregnant rhesus monkeys injected with T
Daughters born with external male genitalia and displayed more ‘male’ behaviours in infancy, e.g. rough play
Foetal testosterone and behaviours: spatial ability (Williams et al., 1990)
Female rats injected with T after birth perform better than other females on maze-learning
Perform as well as male rats who’ve been exposed to foetal T throughout gestation
Foetal testosterone and behaviours: eye contact (Lutchmaya et al., 2002)
girls make significantly more eye contact than boys at 1 year old
Link between prenatal T levels and social development
Measuring foetal testosterone levels: Amniocentesis
Removing a small amount of amniotic fluid from amniotic sac around developing foetus
Commonly used to test for chromosomal disorders + sex
Measuring foetal testosterone levels: 2D:4D ratio
Length of 2nd digit compared to 4th digit
2D:4D ratio negatively correlated with prenatal T levels - lower in males than females
Sporting ability and 2D:4D ratio (Manning & Taylor, 2001).
2D:4D ratio is lower in…
This suggests that…
professional footballers
players in 1st team squads
international players
foetal T promotes development of traits important in male physical display + competition
2D:4D ratio predicts…
financial trading spatial ability aggression personality musical ability sexuality skiing ability sperm production
2D:4D ratio and autism (Manning et al., 2001)
Lower 2D:4D ratio in autistic children, as well as their siblings and parents
A possible early indicator of autism?
