Transcript For indirect reciprocity

Peter Gärdenfors
The role of cooperation in the evolution
of human communication
SEDSU project
Stages in the Evolution and
Development of Sign Use
Work done in collaboration with
Ingar Brinck and Mathias Osvath
at Lund University
Hominin
ancestors
What makes human thinking
so unique?
Levels of
cognition
Levels of
cooperation
Levels of
communication
Prospective cognition
• ”Mental time travel” representing future
needs and events
• Involving ”detached” representations,
suppressing current sensations
• Unique in humans? (the Bischof-Köhler
hypothesis)
• Long ranging life style of hominins
promoted prospective cognition
Oldowan tools ≈ 2.5 Mya
Main components of the
Oldowan culture
Plummer (2004): ”Flaked stones and old bones”,
Yearbook of Physical Anthropology
• Manufacturing and use of stone tools
• Transport of artefacts (at least the stone
tools)
• Transport of pieces of carcasses
• Use of accumulation spots
• Division of labor (?)
Homo transportens
Intersubjectivity:
Components of a ”theory of mind”
•
•
•
•
•
Understanding the emotions of others
Understanding the desires of others
Understanding the attention of others
Understanding the intentions of others
Understanding the beliefs of others
Representing the beliefs of
others: False belief tasks
0. Subjects are three- to five-year-old children.
1. The children are first shown a Smarties tube and then asked
what they think is in it. All the children reply “Smarties” (or
“sweets”).
2. When the tube is opened it is found to contain pencils.
3. Then the tube is closed.
4. The children are now asked what a friend, who has not yet
seen what is in the tube, will say that it contains.
5. The three-year-olds generally answer “pencils” whereas
most of the older children say “Smarties.”
Levels of
cognition
Levels of
cooperation
Levels of
communication
Levels of cooperation
• Ingroup vs. outgroup
behaviour
• Reciprocal altruism
Reciprocal
altruism
I scratch your back
- you scratch mine
Modeled by iterated
prisoners’ dilemmas
Building up trust
between two individuals
Levels of cooperation
• Ingroup vs. outgroup
behaviour
• Reciprocal altruism
• Cooperation about
future goals
• Indirect reciprocity
(the good Samaritan)
QuickTime och en
TIFF (okomprimerat)-dekomprimerare
krävs för att kunna se bilden.
Building a reputation
Nowak & Sigmund, 2005
Connections between cooperation, cognition and communication
Type of coope ration
Ingroup coperation
Reciprocal altr uism
(attitud inal r eciprocity)
Cooperation about future
goa ls
Indirect reciprocit y
Commitm ent and
contract
Cooperation based on
conven tions
Cognitive demands
Recogn it ion of group member
Individu al recogn iti on, mi nimal
memory, reacting to the desires
of others
Individu al recogn iti on, memory,
prospective plann ing, value
comparison, intersub jectivit y
including joint intentions
Individu al recogn iti on, (episodic)
memory, slow temporal
discount ing, reacting to the
emotions and intentions of others
Individu al recogn iti on, memory,
prospective plann ing, joint
beli efs
Intersubjectivit y that all ows
comm on kno wledge
Communicative demands
None
None
Symbolic comm unication
Protolangu age
Symbolic comm unication
Language wit h syn tax for
roles
Symbolic comm unication
Protolangu age
None, but enhanced by
symboli c comm unication
Table 1: The cognitive and communicative demands of different forms of cooperation.
Levels of
cognition
Levels of
cooperation
Levels of
communication
Basic levels of communication
Type of sign (Peirce)
• Signal (index)
• Icon
• Symbol
Type of communication
• Most animal communication
• Mimesis
• Language
– Protolanguage (Tarzan)
– Language with syntax
Communicating about our inner
worlds
Why humans evolved
symbolic communication
(1) The Oldowan culture constituted an
ecological niche containing evolutionary
forces that fostered prospective cognition.
(2) Prospective cognition made cooperation
about future goals beneficial for the
hominins.
(3) Protolanguage is an efficient way of
solving problems concerning cooperation
about future non-existent goals.
Symbols are required for
communication about future goals
• If the goal is present, then signaling is
sufficient.
Joint attention to a referent
Joint attention to a referent
Future goal
Symbols are required for
communication about future goals
• If the goal is present, then signaling is
sufficient.
• If the communicated goal is not present,
detached representations are required. Iconic
miming may work, but only if the signaler and
receiver have sufficient common knowledge
about the goal.
• If the communicated goal is a novel entity that
does not yet exist, combinatorial symbols
(protolanguage) are required.
• Dessalles: Protolanguage can describe scenes.
• Explains why no other species uses symbols.
Building a reputation
Nowak & Sigmund, 2005
Indirect reciprocity requires
language with (minimal) syntax
Communication concerning reputation
requires:
• Reference to individuals in their absence
• Express that “x was good to y” and “y was
bad to x”
• Express that “y has bad reputation”
• Involves marking roles, which is done by
syntax
Two hypotheses concerning
the evolution of language
• Protolanguage is an efficient
system for cooperation about
future goals
• Language with syntax is an
efficient system for maintaining
indirect reciprocity
Possible archaeological evidence
For prospective cooperation:
• Division of labor
• Big game hunting
• Large dwellings
• Marriage (Deacon)
For indirect reciprocity:
• Indications that reputation has social impact
Peter Gärdenfors
The role of cooperation in the evolution
of human communication
Representing the emotions of
others: Empathy
• Empathy: perception of emotion in another
activates the same emotion in the receiver
• Evidence for empathy in mammals
• Speculation: depends on mirror neurons
• Chimpanzees exhibit consolation behaviour
• Cognitive empathy: subjects understand the
emotions of others without having the
emotion themselves
Representing the attention of
others
• Children at 6 months can follow the gaze of
their mother if she turns her head
• At 12 months they can follow the gaze of their
mother if she just moves her eyes
• At 18 months they can follow the gaze of their
mother if she looks outside their field of vision
(requires allocentric representation of space)
• Chimps can also follow gazes in an
allocentric way
Representing the intention of
others
Understanding the pursuit of goals:
• Experiments where an adult (1) deliberately
avoids handing over or (2) fails to hand over
a reward (a toy or food)
• Children from 9 months and chimps react
differently to (1) and (2), i.e. to whether the
failure was deliberate or not
• Is this sufficient to claim that chimps
represent the intentions of others?
How to avoid prisoners’
dilemmas
• Iterated games (trust can be built up)
• ”Guilt aversion” (Charness and
Dufvenberg 2006) changes outcomes of
a prisoners’ dilemma - increases
cooperation
• Presumes understanding desires
• May explain egalitarianism in human
(hominin) societies