At
the end of this Chapter you should be able to:
nLearn about
evolutinary roots of motivated behavior
nLearn about Eating
nLearn about Threat
and Agression
nLearn about Mating
Charles Darwin
nRattled the world with his theory
of natural selection
nWrote “Origin of Species”
Darwin’s Theory of
Evolution
1.
More individuals are born in each species that survive to sexual maturity.
2.
There is variation among the individuals of all species; indeed, no two
individuals are identical.
3.
Certain differences among individuals are adaptive. The individuals who
possess the adaptive characteristics are more likely to survive and reproduce
in the environment into which they are born.
4.
Some adaptive differences among individuals are inherited.
Darwin’s
Theory of Evolution
5.
The environment does not contain enough resources to support all individuals.
6.
A struggle for existence occurs among individuals; those who possess the most adaptive characteristics, by
definition, win the struggle.
7.
Individuals who survive and reproduce pass on their adaptive characteristics to
their offspring, who are more inclined to inherit these adaptive traits than
the offspring of parents who do not possess them.
8.
Over many generations, this process may result in the creation of new species.
Biological
Perspective
nThe biological perspective leads us to ask how various behaviors came to
be – how they evolved and what purpose they serve.
nWhat do we share with other species – e.g., A sense of curiosity, a
sense of play etc…
nWhat do we not share with other species – e.g., language?
Evolution
of Behavior
nMany aspects of who we are and how we behave are rooted in our genetic
heritage.
nIdentical twins inherit exactly the same genetic pattern. This makes
a difference! Identical twins usually end up more similar to each other in
their personalities and preferences than are other siblings, even when they are
raised apart (in different households).
Evolution
of Behavior: The Comparative Method
nWe can get further insights into the evolution of behavior by comparing
human behavior to other organisms.
nIf we find parallels between, say, human aggression and aggression in
other species, this would strengthen the belief that OUR aggression is fueled
by genetic forces that operate on all species.
lOther animals are less likely to be influenced by cultural factors or
complex decision-making. Therefore finding parallels with other species would
suggest a smaller role for these human (cultural) influences.
EATING
Built-in system for regulating food intake
Maintain genetically determined set points
la weight the body tries to maintain (the target)
Eating
nLiver
nHypothalamus
nStomach and Duodenum
nAdipose Tissue
Liver
Maintains constant level of glucose in bloodstream
Too much glucose detected…
Glucose turns into glycogen and fatty acids
Liver signals to stop eating
Not enough glucose detected…
Stored glycogen and fatty acids turn back into glucose
Liver signals to eat
Hypothalamus
Contains glucoreceptors
Also sensitive to glucose levels in the blood
Sends signals similar to that of the liver
Stomach and Duodenum
Contains receptors sensitive to
nutrients
dissolved in digestive juices
Stops signaling hunger when proper nutrients are on the way
Adipose Tissue
Stores fat in cells to be used when glycogen runs out
Secretes leptin
when cells are full
Chemical that indicates when no more fat storage is needed
Why so
many signals?
nSafety provided by
backup systems
lIf one system
fails, the organism is still protected
nDifferent signals
monitor different aspects of our nutritional needs
lLeptin-longer term
needs
lOthers (cues from
stomach)-hour-by-hour energy requirement variations
Aside from our internal structures, what
else can
influence what and when we eat?
nImmediate outside
influences
nCulture
nSocial
nCognitive
Obesity
Obesity is an eating disorder. We need to consider
multiple factors if we want to understand eating behavior.
Is it because we eat too much?
Some people are predisposed to obesity due to their
individual genetic pattern (i.e., set points).
QUIZ !!!
How did your body react…
nWhen I first announced the quiz?
nAfter you were informed that it would not be taking place?
The
Autonomic Nervous System
nAll mammals (and
all birds) are endotherms; organisms that
maintain stable body heat.
nEndothermic animals
sometimes become too warm ; and so need to lose heat and sometimes too cold and
so preserve the heat created by their own metabolic activity
nThese two
activities are controlled by the autonomic nervous system
Autonomic Nervous System
Central Nervous System (CNS)
lThe brain and spinal cord
Peripheric Nervous System (PNS)
lSystem of nerves outside of the brain and spinal cord
lSend control to the glands and smooth muscles
lControls internal organs, usually not under voluntary control
nThe peripheral nervous system
is subdivided into the:
nsensory-somatic nervous system and the
nautonomic
nervous system
lTwo branches
nSympathetic
nParasympathetic
Sympathetic Nervous System
nTriggered when body temperature is too low
nRevives up body activity
to prepare for rigorous activity
nIncreased heart
rate
nSlowing down of
peristalsis (rhythmic contractions of intestines), so not using energy during
digestion
nVasoconstriction
lContraction of
skins capillaries
Parasympathetic Nervous System
nTriggered when body’s temperature
is too high
nRestored body’s internal activities
nCardio slowing
nSpeeds up
peristalsis
nVasolidation
lWidening of skin’s
capillaries
THREAT AND AGGRESSION
What happens biologically when we feel threathened?
Self-protection
The Emergency Reaction: Fight or Flight
Intense arousal serves as an emergency reaction that mobilizes the animal for a crisis.
Internal adjustments necessary to respond to threat in
environment
When threat detected: Sympathetic branch of ANS activated
Prepares body for immediate, intense activity. Surge of adrenaline
released
Male
aggression and hormones:
The male is the far more aggressive sex. This gender
difference holds only for physical aggression. Testosterone (the male sex
hormone) is associated with physical aggressiveness in many species.
Territoriality:
Acquisition and protection of resources, usually
territory: source of most aggression
Often expressed in humans as “personal space” preferences
Vary by culture; much is learned
Male
versus female aggression:
Males use physical aggression (pushing and punching).
Females use social aggression (spreading gossip and rumors, isolating unwanted
friends).
Learning
to be aggressive?
1. Explicit learning:
someone demands or teaches us
2. Implicit: we
observe
3. Seems to be causal;
when we observe violence, we become violent
Is
aggression inevitable?
Cultural values, testosterone, defending your territory,
revenge etc...
If your opponent is stronger than you are, then you better
not start the battle at all! This is a limit on aggression. Dominance hierarchy:
who is the strongest in the group? Assigned status is a limit on aggression.
Nature-Nurture Debate
Relative importance of an individual's innate qualities (“nature”) versus personal experiences (“nurture”) in determining individual differences in behavioral traits.
MATING
nAppearance
nMatching
nGender Differences
Appearance
Humans value attractiveness in a partner
Who is attractive?
Isn’t beauty the eye of the beholder?
Facial Appereance
nCross-culturally
lShiny hair
lNo visible
deformities
lClear skin
lSymmetrical face
lAverage face (slight deviation can help)
nDevelopmentally
Infants
nInfants as young as
3-months-old look longer at adult-rated attractive faces
Pictures?
n12-month-olds interact more
positively with
adult wearing “attractive” mask.
Why is there a preference for attractiveness?
Indication of health
Body Appearance
nWomen
lNot size
lWaist-to-hip ration
lMature pelvis adequate fat supply
lFertility and readiness for pregnancy
Just how innate are these preferences?
nNot a strong relationship between facial attractiveness and
health
The Matching Hypothesis
nThere is a strong correlation
between the
level of attractiveness of two partners
nPrefer partners similar to
themselves
The Matching Hypothesis
nAttractiveness
nPersonality
nRace
nEthnic origin
nSocial status
nEducation level
nFamily background
nIncome
nReligion
nHabits
Gender differences in mate selection
/ Animals
nFemales
lDecide when to mate and mating partner
lMost physical investment in breeding
nMales
lAdvertise sexual availability
Gender differences in mate selection
/ Humans
Man seeking
woman…
nPhysical attractiveness
lHealthy and fertile
nYouth
lMore reproductive years
nKindness
nIntelligence
nLess value of commitment
nMore jealous by sexual disloyalty
Women seeking men…
nOlder
nSocial and financial status
nBetter ensures offspring’s survival
nKindness
nIntelligence
nMore value of commitment
nMore jealous of emotional disloyalty
A Critique of the Evolutionary Perspective
nTo what degree are we influenced by inborn mechanisms? – The
evolutionary perspective assumes that most behaviors are inborn. Tries to
explain it from an evolutionary perspective by using the comparative method
(compare other animals’ behavior to humans’).
nWhy is it hard to test evolutionary arguments’ claims? – We don’t know
how our ancestors used to behave. Fossils don’t give us behavioral
evidence.
nWhat is the evolutionary perspective’s contribution to psychology? –
Introduces new questions, new data, into psychological arguments.
Final
Thoughts: Biological Perspective
nBiological perspective: underlying mechanisms of behavior in the body,
comparison to other species, an exploration of the evolutionary forces that
shape behavior.
nIn basic biological functions like eating, sexual behavior and
aggression, most animals are in control of the same biological forces that are
shaped by evolution.
nHow do you understand obesity from a biological perspective? Look at a
person’s genes! But also understand the interaction between genes and person’s
life situation.
nBut behavior is also shaped by our individual experiences and the
circumstances we live in.
nSO DOES PSYCHOLOGY NEED TO BE A BIOLOGICAL SCIENCE? Yes!!! But only in
part.
Contribution of Biological Perspective
nBiological perspective: much to teach us about mechanisms, evolutionary
influence on behaviors
nNo aspect fully explained by
biological perspective
nFocus thus far: large scale processes/mechanisms
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