Human Behaviour
Introduction:
- behaviour is determined by a complex interplay of:
Evolutionary
biological determinants of human cognition & behaviour:
- much of what follows below on innate determinants is speculative at this stage based on theories
espoused in the The Red Queen
and Desmond Morris' 'The Naked Ape' & partly summarised in evolution of human
sexuality which takes a comparative anatomy/physiology evolutionary
approach to human behaviour.
- 2 million years of males as a hunter and females as
nurturers/communicators has resulted in specific gender differences in
neural wiring which is mediated via:
- foetal brain being initially female-type but if exposed to
testosterone from 6-8wks becomes male-type
- testosterone is produced by the foetal testis after testis-determining factor
(TDF) (produced from Y chromosome)
stimulates development of Leydig cells in
the 7th-8th weeks of gestation causing
the cortex to regress and the medulla to
develop into a testis
- depending on the degree of testosterone exposure at this critical
time determines the degree of male-type wiring that develops
- 15-20% of males have feminised brains whilst 10% of females have
masculinised brains
- intelligence genes are mainly on the X chromosome which results in females
having a lower variation in IQs than males and a slightly higher average IQ
as males with only one X chromosome are highly dependent on it being a good
intellectual one and thus there are more males with very low IQ and very
high IQ than females.
- "male-type" neural wiring characteristics:
- better long distance visual acuity to see & track potential prey
- better spatial orientation skills & can think in 3 dimensions
- map reading without having to turn map upside down
- driving at speed around curves
- parallel parking
- determination of source of sounds
- little need for speech complexities other than to convey factual
information succinctly
- brief, direct & accurate sentences that mean what they say
- tend to choose greeting cards with lots of words so they don't
have to write so much
- by puberty are thicker skinned with less touch sensation so can
respond to painful stimuli better & tend to avoid touching other
people
- risk-taking behaviour
- to help them go out on 3 day missions to find food or starve to
death
- aggression
- to compete with other males & tribes for scarce food & to
kill prey
- power & status are important
- suspicious, controlled loner but able to work well with other men
to hunt prey in organised fashion => desire for team sports
- continuous sex drive
- ensure survival of species by always being ready to procreate
- tendency to polygamy to spread the seed - wired to seek out and
mate with as many healthy females as possible
- readily visually aroused with brief cold start to orgasm times to
minimise danger of being caught in vulnerable state
- when constrained to monogamy males:
- need variety to fool their brains that they are mating different
women eg. different lingerie; different places; etc.
- are highly likely to break constraints even at risk of
substantial penalties
- silent problem solving cognition
- cognition tends to be predominated by problem solving which is
usually done alone and in silence (hence Rodin's "The
Thinker") whereas women tend to need to verbalise their
problems before they can solve them
- tend to offer solutions to women rather than just listen to them
verbalising their problems
- defender instinct
- tend to sit with back to walls in restaurants whereas women only
tend to do this if they are alone with children
- sleep on the side of the bed closest the door
- awake to sounds like twigs breaking rather than to babies crying
- minimal emotion expressed
- hate to be seen to be wrong & hate criticism
- need to be seen as strong and capable without weaknesses
- prefers objects to people
- value occupation over relationships
- "female-type" neural wiring characteristics:
- better peripheral vision (almost 180deg. ) to watch for predators
& keep eye on children
- young girls less likely to be killed as pedestrians than boys,
& women less likely to be hit from the side in car accidents
- women can perve on guys without getting caught
- women are better able to find things in cupboards & fridges
- improved colour vision due to greater variety of retinal cone cells
(retinal cones are on X chromosome)
- better night vision but not good at night driving as lack spatial
abilities required to assess movement of other cars especially at
distance
- better close vision thus better at needlework, etc
- greater amount of whites in eyes to allow improved eye signalling
& female bonding
- better attention to non-verbal communication signals
- improved assessment of relationships, psyche, etc
- better at detecting lies
- improved hearing especially of high pitched sounds
- can better detect a baby's cry when sleeping
- improved listening skills
- girls listen to conversations better & can perform other tasks
simultaneously whereas males need to stop reading to listen
- improved speech skills
- better at communicating emotions
- tend to talk indirectly which builds relationships & rapport
with other females by avoiding aggression & confrontation or
discord
- mothers & sisters will generally speak for a young boy as his
speech tends to be delayed and often malformed with stuttering, etc
- greater number of corpus callosum fibres allow multi-tasking of
unrelated events
- can listen to more than one sound at a time
- multiple children talking concurrently
- can brush teeth up & down in one hand while polishing a table
in circular motions in other hand
- can talk while performing tasks more readily eg. whilst having sex
- more sensitive skin to light touch and pressure
- oxytocin stimulates touch receptors & in turn its production
is increased by touch
- females are 4-6x more likely to use touch in same sex social
conversations as males
- children require touching for mental development
- better sense of smell & taste,
- especially sweet as need to test food for ripeness
- smell is even better around ovulation when it can subconsciously
detect male pheromones in potential partners and determine the state
of his immune system and his genetic compatibility
- prefers people to objects unless the objects are baby-like such as
teddy bears
- tend to adopt cooperative rather than competitive relationships
- value relationships over occupation:
- when constrained to monogamy:
- highly likely to break constraints despite potential penalties
- XY chromosomal abnormalities:
- Turner's syndrome (XO)
- short, webbed neck, fail to develop at puberty, normal IQ but very
poor at maths, spatial & visual perception
- Klinefelter's syndrome (XXY)
- physically male with aspermic small testes & penis but with
marked feminine characteristics incl. breasts
- 50% are mentally retarded
- XYY
- supermales - high levels of testosterone lead to aggression, high
sex drive, precocious puberty, tall => crime rates higher
Hormonal
& neurotransmitter influences on behaviour:
Testosterone:
- apart from its in-utero impact in creating male-pattern neural wiring its
presence in later life acts to magnify the effects of male-pattern wiring:
- aggression
- sex drive in males
- improved spatial abilities
- decreased verbal abilities
Oestrogen:
- apart from its in-utero impact in creating female-pattern neural wiring
its presence in later life acts to magnify the effects of female-pattern
wiring:
- improved verbal skills
- improved fine motor skills
- improved memory
- overall feeling of contentment & well-being
- nurturing & nest-building behaviours
- increased sex drive at ovulation??
- ? improved pheromonal sensitivity to detect compatible partner
Progesterone:
- releases parental & nurturing feelings
- ? improved pheromonal sensitivity to people with similar genes eg. child
& dislike for others including spouse
Oxytocin:
Phenylethylamine (PEA):
- related to amphetamines & found in chocolate
- released in the brain when you fall in love & cause the physical
feelings of being in love - tachycardia, sweat, pupil dilation, butterflies
in stomach
DHEA:
Pheromones:
- most animals have a pit-like structure in the vomeronasal organ that
transmits neural messages to the hypothalamus in response to pheromones,
however, humans do not have any of these neural connections, nevertheless,
it has been shown by PET brain scans in 2005 that homosexual men &
heterosexual women have anterior hypothalamic activation in response to
smelling the putative pheromone 4,16-androstadien-3-one (AND), a derivative
of testosterone found in sweat, whilst heterosexual males due to respond to
it. Likewise male's anterior hypothalamus is stimulated in response to
smelling a corresponding compound in female urine called EST.
- it is thought by many that pheromones may have roles in:
- altering behaviour towards other people:
- before & during ovulation, drives a sexual attraction for
persons of "different" pheromonal molecular structure to
increase likelihood of genetic diversity in mating
- during progestational stages (& thus pregnancy and OCP),
drives a need to be with persons of "similar" pheromonal
molecular structure - ie. mothers, children
- thus potential perhaps for meeting the "wrong"
genetic man if meet him 1st while on OCP! ?????
- synchronising menstrual cycles between women who live in same
household
-
a mutation in human serotonin transporter gene (hSERT) which increases
serotonin transport appears to be a key factor in obsessive-compulsive behaviour
disorder and is perhaps also related to associated disorders including anorexia
nervosa, Asperger's syndrome, social phobia, tic disorders, alcohol & drug
abusers.