Lecture 9: reciprocity

Question 1

reciprocity =

Answer 1

you scratch my back, i’ll scratch yours (Trivers 1971)

Question 2

theory in explaining reciprocity just with two players

Answer 2

the prisoner dilemma 
-2 players 
-cooperate/defect 
-TABLE 
T>R>P>S

Question 3

the prisoners dilemma: in single encounters or fixed number of encounters defect is

Answer 3

always ESS

Question 4

the prisoners dilemma: if repeated, indeterminate encounters

Answer 4

escape the dilemma

Question 5

‘Tit for Tat’ strategy

Answer 5

in prisoners dilemma game

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

Question 6

evidence of reciprocity: Vampire bat

Answer 6

(wilkinson 1984)
-unsuccessful foragers are fed by successful ones
- is a low level of relatedness
3 keep points a to y:
-high chance of future interaction
-benefits to recipient high, cost to donor low
-donation of blood is reciprocated

Question 7

criticism of wilkinson 1984 study =

Answer 7

• sharing is kin selected
• sharing with non-kin is coercion, mistaken identity or indiscriminate altruism within kin groups (bullied into it)
• wilkinson did experiment to argue these and proved the criticism wrong

Question 8

primate grooming and alliances is evidence for

Answer 8

reciprocity

-seen in baboons and vervet monkeys

Question 9

vervet monkeys and reciprocity

Answer 9

• grooming

- but also recent grooming by subordinates increased dominants tolerance of them at a food source

Question 10

reciprocity example in birds

Answer 10

• predator mobbing in birds (Krams et al 2008 )
• to drive predator away, surround and make lots of noise
• pied flycatcher
• 3 pairs,
  1st exp 1 pair locked away, 1 mobbed, other helped
  2nd exp, all free, 2 mobbed, helped the one who helped before not the one locked away

Question 11

general conclusions to reciprocity:

Answer 11

1) limited evidence
2) interactions are rarely dyadic (2 player game) – biological markets
3) defection PUNISHED/ cooperation ENFORCED
- -cheating has high costs

Question 12

biological markets =

Answer 12

Noe & Hammerstein 1994,1995
whole network of soil partners
-develop profitable relationships
- terminate unproductive ones

Question 13

biological market theory evidence

Answer 13

Macaque mating market (Gumert 2007)

• grooming for sex
• over a 1/3 grooming of females by males led to mating
• grooming duration related to female supply (less F =longer)

Question 14

types of reciprocity:

Answer 14

• Direct reciprocity
• Generalised reciprocity ‘help anyone if helped by someone’ (rats labs exp to support it)
• indirects reciprocity ‘help someone who is helpful’

Question 15

generalised reciprocity lab exp

Answer 15

Norway rats in lab (Rutte & Taborsky 2007)

• 2 rats, can feed each other but not themselves
• pulling freq 21% higher after experiencing help

Question 16

punishment in reciprocity

Answer 16

Clutton-Brock & Parker 1995
to ensure reciprocity 
- --> ++
- --> -- (cost to punisher must be < punished)
\++

Question 17

Punishment in nature Dinoponera ants =

Answer 17

Monnin et al 2002

• no queen
• dominant female (alpha) reproduces
• if challenged, alpha marks challenger who is then PUNISHED by other females

Question 18

punishment in humans

Answer 18

• contributions to honesty box in university coffee room
• 2 images (flower/eyes)
• eyes = more money put in

Question 19

current evidence suggest reciprocity is not widely ____

Answer 19

important EXCEPT in humans