PSYC 205 Study Guide - Quiz Guide: Net Energy Gain, Nash Equilibrium, Matching Law

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Chapter 7 Decision Making
- Choice: the outcome of decision making, measured as a motor action or verbal
- Decision-making is an inherited trait, shaped by natural selection  questions whether
we have free will
- Free will: humans strongly believe that their actions are based on free will, even while
recognizing that some behaviours occur unconsciously.
- Brain images challenges free will  Brain activity related to behavioural choice
occurs prior to conscious awareness of the choice
- Individual differences in responses. Individuality adaptive because predictability
is seldom advantageous
Optimal Foraging Theory
- Foraging behaviours  amount of energy acquired during food consumption is offset
by the energy expended to obtain it
-Optimal Foraging Theory: suggests organisms forage in a way that maximizes net
energy gain per unit time
-Central Place Foragers: an animal that carries food back to a home base, such as a
nest or burrow, to horde or consume it (ex. chipmunks the further the distance to
home, the more seeds they carry in their cheeks)
oHumans do this with convenience/grocery stores
-Handling: the time & energy required to extract a consumable food item from its
- Sometimes optional foraging not followed (ex. few medium vs. many large
mussels presented to crabs)
oExplanation: animals make errors when discriminating large/small prey or
may not remember handling times of different types of prey
oOptimal foraging compromised if predators around
- Foraging success = greater fitness = natural selection
Marginal Value Theorem
- Food distributed in patches, not evenly
-Marginal Value: the point at which foraging in one patch yields a net energy gain
that is lower than the average gain of the habitat (patch gets depleted of food &
it’s no longer advantageous to stick around)
oWhen foraging in a patch declines below marginal value, animals move to
another patch  optimizing net energy
oHow soon an animal moves on depends on how far away the next patch is
- Animals sample resources in different patches to update ideas of resource content.
Aids in decision of where to move next
oAnimals must divide their time between remaining in the most profitable
patch and sampling nearby patches
-Deviations from marginal value theorem rarely occur, but if they do its usually
because moving to a new patch involves unknown risks, like predation, or
alternatively the necessity of searching for mates
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Ideal Free Distribution Model
-Looks at group decision making
-Best strategy = divide between patches, otherwise resources depleted quickly in
each patch
-The Ideal Free Distribution Model: a theory explaining how conspecifics divide
themselves during group foraging; the number of animals aggregating at a
particular food patch is proportional to the amount of resources available at that
o This was proven with stickleback fish & bumblebees
oException: sometimes less animals gather in a patch with fewer resources.
This usually occurs because socially dominant conspecifics have declared
resource-rich areas theirs. Other restrictions = social (ex. caring for young)
-The Nash Equilibrium:
oGroup decision making has reached a Nash equilibrium if no single
individual in the group can improve their payoff by unilaterally changing
their strategy (no point in changing own strategy because others remain set
on their decision)
o Ex. ducks distribute themselves in a way that every group member
Collective Decision-Making
- Impact of social interactions on choice behaviour  although each group member
only has access to portion of information needed to guide behaviour,
direct/indirect interactions between individuals lead to group cohesion/acting like
a group unit
-Evolved from coordinated behaviour  advantages of synchronized group activity
-Single defector will not alter behaviour of the group
-Increased group size increases accuracy of group decisions  group choice more
effective & efficient than individual
oLeadership unnecessary
-Neural decision-making: inactive neuron stimulated AP refractory period
-Collective decision-making distinct from cooperation. Cooperation = immediate
gain for all actors, not necessarily true for collective decision making
oDefection disadvantageous in cooperation, but no consequences in
collective decision making
-Overall, social insects rely on collective decision making, not cooperation
Beyond Foraging
-Optimal energy expenditure applies to reproduction, habitat selection & aggression
-Optimality theories 3 components: a choice behaviour, currency that allows costs &
benefits to be compared, and cognitive & environmental constraints that alter the
relationship between these 2
-Decision-making a learning process, allowing adaptation to changing conditions
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