HPS111 Lecture Notes - Lecture 11: Motivation, Leptin, Orexigenic
WEEK 11
Motivation – a process that influences the direction, persistence and vigour of goal directed behaviour.
Perspectives on motivation:
a. Instinct (fixed-action pattern) – an inherited characteristic, common to all members of a species, that
automatically produces a particular response when the organism is exposed to a particular stimulus.
b. Homeostasis – a state of internal physiological state of equilibrium that the body strives to maintain.
Maintaining homeostasis requires a sensory mechanism for detecting changes in the internal environment.
Hull’s ‘drive theory of motivation’ – claims that physiological disruptions to homeostasis produce ‘drives’
(states of internal tension that motivate an organism to behave in ways that reduce this tension). E.g. drives such
as hunger and thirst pushes an organism into action.
c. Approach/Avoidance motivation:
Behavioural activation system (BAS) – ‘Approach motivation,’ neural activity in the left prefrontal area is
activated by signals of potential reward and positive need gratification. Causes the person to start or increase
movement towards reaching positive goals in anticipation of reward. It produces emotions of hope, elation and
happiness. People high in BAS prefer novelty and change.
Behavioural inhibition system (BIS) – ‘Avoidance motivation,’ neural activity in the limbic system and the
right frontal lobe is activated by signals of potential pain, non- reinforcement and punishment. Causes escape,
avoidance and inhibition (freezing in terror) behaviours and emotions of fear, depression and aversion. People
high in BIS prefer familiarity.
d. Cognitive processes:
oIncentive – represents environmental stimuli that pulls an organism towards a goal.
oExpectancy x value theory – claims that goal directed behaviour is jointly determined by the strength of
the person’s expectation that particular behaviours will lead to a goal and by the incentive value he/she
places on that goal.
oExtrinsic motivation – performing an activity to obtain an external reward or avoid punishment. E.g. a
student who studies very hard solely to get good grades.
External regulation – behaviour is motivated by desire to receive external rewards or avoid punishments. E.g.
studying to get a higher degree solely because you want a higher-paying job
Introjected regulation – behaviour done out of internalised reasons (doing it because you feel that you should
do so). E.g. studying because your parents expects you to do so and not doing it will make you feel guilty for
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letting them down.
Identified regulation – behaviour is done out of choice but is not enjoyed by the individual. E.g. an athlete who
doesn’t like going to the gym at 6am does so in order to be a better athlete
Intrinsic motivation – performing an activity for its own sake, because you find it enjoyable or challenging.
Internal regulation – behaviour is done for its own sake because it brings you joy, self-fulfilment and
stimulation.
Amotivation – behaviour has no real motivational purpose, and people either discontinue or do it out of
routine/habit.
Psychodynamic views – Freud proposed that energy from unconscious motives – especially sexual and
aggressive instincts – is often disguised and expressed through socially acceptable behaviours. E.g. to be a trial
attorney or an athlete.
Maslow’s need hierarchy – a hierarchy containing deficiency needs (needs concerning physical and social
survival) at the bottom and uniquely human growth needs at the top. Self-actualisation – represents the need to
fulfil our potential. Maslow considered this the ultimate human motivation.
Humanistic theory of motivation:Self-determination theory – focuses on three fundamental psychological
needs including competence, autonomy and relatedness, and how they relate to intrinsic and extrinsic
motivation.
Competence motivation – reflects a basic human need to experience oneself as capable, to master new
challenges, and to perfect skills.
Autonomy motivation – i.e. self-determination, satisfied when people experience their actions as a result of
free choice without external interference.
Relatedness motivation – refers to our desire to form meaningful bonds with others, i.e. to care for and be
cared for.
Relations between extrinsic and intrinsic motivation:
Introducing extrinsic rewards for the performance of intrinsically motivated behaviours can result in reduced
motivation and performance if external reinforcer is removed. Extrinsic rewards can weaken self-determination
and thereby reduce intrinsic motivation.
Extrinsic rewards can also enhance intrinsic motivation for a behaviour, if the external reward is perceived as
evidence of mastery and thereby satisfying the person’s need for competence, making the activity enjoyable in
its own right.
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Hunger and weight regulation:
Metabolism – is the body’s rate of energy (or caloric) utilisation.
Satiety – the state in which we no longer feel hunger.
Set point – a biologically determined standard around which body weight (i.e. fat mass) is regulated. Implies
that if we overeat or undereat, homeostatic mechanisms alter our energy utilisation and hunger so as to return us
close to our original weight.
Glucose – a simple sugar that is the body’s and brain’s major source of immediately usable fuel. Changes in the
supply of glucose available to cells provide a signal that helps the brain regulate hunger.
Insulin – a hormone secreted by the pancreas that helps convert glucose into fat.
Cholecystokinin (CCK) – a peptide (type of hormone) that helps produce satiety. CCK and other peptides are
released into the bloodstream by the small intestine as food arrives from the stomach. These peptides travel to
the brain and stimulate several regions that decrease food intake.
Leptin – a hormone secreted by fat cells, enters the bloodstream and reaches the brain where it decreases
appetite and increases energy spending. Leptin increases appetite by increasing the potency of other satiety
signals. Lower leptin levels may tell the brain that there isn’t enough fat tissue, so it’s time to eat again.
Ob gene – an obesity gene which normally directs fat cells to produce leptin. A mutation of the Ob gene result
in a lack of leptin, meaning the brain doesn’t receive any satiety signals and thus the organism continues eating
and in turn become obese. However, leptin injections can be given to obese mice with the Ob gene mutation to
reduce appetite.
Db gene – mutation in this gene causes brain receptors to be insensitive to leptin, thus organisms with this
gene mutation have ample leptin supply but is still obese because the brain cannot detect it.
Brain mechanism controlling hunger:
Lateral hypothalamus (LH) – the ‘hunger on’ centre in the brain, experiments with rats showed that
electrically stimulating it would cause the rats to start eating and lesioning/damaging it would cause it to refuse
to eat to the point of starvation.
Ventromedial hypothalamus (VMH) – the ‘hunger off’ centre in the brain, experiments with rats showed that
electrically stimulating it would cause even a hungry rat to stop eating and lesioning/damaging it would cause
gluttony.
Further research has showed that although the LH and VMH play important role in hunger regulation, they
aren’t really hunger on and off centres. Paraventricular nucleus (PVN) – a cluster of neurons packed with
receptor sites for various transmitters that stimulate or reduce appetite. The PVN integrates several short-term
and long-term signals that influence metabolic and digestive processes. Neuropeptide Y – a chemical
transmitter and powerful appetite stimulant signalled by the PVN. An increase in this transmitter will increase
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Document Summary
Motivation a process that influences the direction, persistence and vigour of goal directed behaviour. Instinct (fixed-action pattern) an inherited characteristic, common to all members of a species, that automatically produces a particular response when the organism is exposed to a particular stimulus. Homeostasis a state of internal physiological state of equilibrium that the body strives to maintain. Maintaining homeostasis requires a sensory mechanism for detecting changes in the internal environment. Hull"s drive theory of motivation" claims that physiological disruptions to homeostasis produce drives" (states of internal tension that motivate an organism to behave in ways that reduce this tension). E. g. drives such as hunger and thirst pushes an organism into action. Behavioural activation system (bas) approach motivation," neural activity in the left prefrontal area is activated by signals of potential reward and positive need gratification. Causes the person to start or increase movement towards reaching positive goals in anticipation of reward. It produces emotions of hope, elation and happiness.
