Reciprocity

Question 1

Common in human societies:

A helps B today, then B helps A tomorrow

Answer 1

What about in other animals? - theory

- evidence

Question 2

The prisoner’s dilemma

Answer 2

always more beneficial and ESS to defect because it’s single encounter

Can escape the dilemma with repeated, indeterminate encounters

Question 3

‘Tit for tat’ strategy

Answer 3

• cooperate on first move, then do what partner did
• can be ESS if probability of re-encounter is high
• depends on social organisation, longevity, etc

Question 4

Vampire bats

Answer 4

Unsuccessful foragers are fed by
successful ones in roosts
Low average relatedness in roost - kin more likely to swap blood
The donors are well-fed, therefore a small amount of blood will benefit their hungry kin much more than it will benefit themselves

But:
high chance of future interaction
benefit to recipient high, 
cost to donor low
donation is reciprocated

Question 5

Follow-up study on vampire bats

Criticisms of Wilkinson study:

• sharing is kin-selected
• sharing with non-kin is coercion, mistaken identity or indiscriminate altruism within kin groups

Answer 5

Blood donation depended mostly on whether the donor previously received blood

Question 6

Tolerance traded with grooming in wild vervet monkeys

Answer 6

Recent grooming by subordinates increased dominants’ tolerance of them at food sources

Question 7

Predator mobbing in birds (Krams et al. 2008)

Answer 7

Birds were more likely to mob predator at neighbours nest if neighbour was a co-operator

Question 8

Reciprocity has limited evidence

Answer 8

because interactions are rarely dyadic (impossible to develop profitable relationships and terminate unproductive ones)

Question 9

Reciprocity

Answer 9

Holding class - holds access to social commodity

Demanding class - seeks access to social commodity

Trade dynamics - supply and demand, advertisement, commodity value

Male-to-female grooming
89% to receptive females
37% led to mating
Grooming duration decreased related to increased supply of females

Question 10

Direct reciprocity

- ‘you scratch my back, I’ll scratch yours’
- as described so far

Indirect reciprocity
‘help someone who is helpful’
- reputation may be important in social interactions
- can work in theory, some evidence (lecture 5)

Answer 10

Generalized reciprocity

- ‘help anyone if helped by someone’
- can work in theory, one good supportive lab expt

Question 11

Defection PUNISHED / cooperation ENFORCED

Answer 11

• cheating has high costs

Question 12

Punishment eg

Answer 12

Dinoponera ants
(Monnin et al. 2002)
No queen
Dominant female (alpha)
reproduces
If challenged, alpha marks challenger who is then PUNISHED by other females

Question 13

Current evidence suggests reciprocity is not

widely important

Answer 13

(except in humans)