Lecture 8: Due before class on 8th
MOTIVATION
- Motivation – A process that guides behavior toward
a goal, and dissipates once the goal is reached
- Motivation and emotion give impetus to behavior
- Motivation Maintains , or internal
equilibrium. E.g. temperature nutrient content,
etc.
- - individuals are motivated to
maintain a certain set point to maintain equilibrium.
- Clark Hull felt that an internal state called drive
motivates organisms to seek or avoid important
things
- When the important stimulus is obtained individuals
experience .
- Other psychologists feel external incentives can
pull organism toward performing a behavior
- rewards – rewards that are
inherent in activity, e.g. pride in a job well done, fun
of a sport.
- rewards – rewards that are
external to a task, e.g. money, praise.
- Extrinsic rewards can sometimes undermine intrinsic
rewards
- In a study, children that already enjoyed playing with
parkers played with them less if they were told they
would get a certificate
HUNGER
- How much and when do we choose to eat?
,- Internal cues – feelings of hunger, stomach
grumbling or contracting, low blood glucose
o Stomach contractions alone don’t lead to
hunger…individuals who have had their
stomach removed !
- External Cues – Time of day, social cues, sight and
smell of food.
- hypothalamus – the gas pedal.
If it is electrically stimulated, rats will overeat
and become grossly overweight. If it is destroyed,
rats eat and drink very little.
- hypothalamus – the brake
pedal. If it is electrically stimulated, eating and
drinking are suppressed. If it is destroyed, rats
overeat.
,- - simple sugar that enters the blood during
digestion.
- We tend to feel hungry when we have low blood glucose (not the
whole story…)
- - hormone secreted by pancreas that assists
with transfer of glucose from the blood into cells.
- People with diabetes either don’t produce enough insulin, or their
cells are immune to it.
- Despite high blood sugar, diabetics still report feeling hungry
- Hunger might
result from
how
available
glucose is to
cells, rather
than
simply how
much is in the
blood.
Amount of insulin in the blood after a meal for a
diabetic and non-diabetic. Fill in the graph
, - - a hormone secreted from well-
nourished fat cells that increases metabolism and decreases
eating.
- Mice with a genetic mutation that prevents fat cells from secreting
leptin have low metabolisms, overeat, become obese, and tend
to develop diabetes.
- If given leptin injections, their weight returns to normal.
- Ghrelin – a hormone released by the gastrointestinal system
when the stomach is empty
- Ghrelin increases when fasting, decreases after a meal
- In a study with humans, an injection of ghrelin
and elicited vivid images of preferred
foods (Schmid et al. 2005)
- Ghrelin administered to laboratory animals causes them to
eat more than usual and gain weight