PROTO-HUMAN COGNITION IN
NON-HUMAN ANIMALS
James R Hurford
Language Evolution and
Computation Research Unit,
University of Edinburgh
Descartes
Animals as automata, and humans as automata+Reason
Darwin
Humans are evolutionarily related to apes and all other
animals.
Morgan's Canon
“In no case is an animal activity to be interpreted in terms of
higher psychological processes, if it can be fairly interpreted
in terms of processes which stand lower in the scale of
psychological evolution and development.”
Anthropomorphism versus continuity
Seeds of language:
precursors of aspects of language in animal life
• object permanence,
• episodic memory,
• metacognition,
• competence with abstract relations,
• transitive inference,
• subitizing,
• the where/what-dorsal/ventral separation,
• global and local attention.
• `frame-of-reference' systems,
Displaced reference
Human language enables us to refer to
things distant in time and space.
No animal communication system allows the
animal to refer to distant things,
(except honeybee communication).
But many animals can solve object
permanence tasks.
Relative performance on object permanence
Species
Visible/invisible
Domestic chicks Neither
How long?
Squirrel
monkeys
Visible only
Cotton-top
tamarins
Parrots
Both
Dogs
Both
Up to 4 mins
Chimpanzees
Both
Overnight
Humans over 3
Both
Very long times
Both
A solipsistic, private view of the origins
of reference.
Private attention to objects (visible or hidden) is
the basis for later-evolved public reference to
objects (e.g. via language).
Animals’ abilities in object permanence tasks are
the evolutionary seed of displaced reference in
language.
Episodic memory (mental time travel)
Humans describe specific events, often in the distant
past (or future).
Tulving (and Suddendorf) claims that episodic
memory is unique to humans.
But there are degrees of ‘episodic-like’ memory.
‘Episodic-like’ memory in animals is usually restricted
to the domains animals are interested in (e.g. food).
Clayton et al.: Scrub jays remember where they hid food, of
what type and how long before.
Schwartz & Evans: apes have episodic-like memory.
MacDonald: Gorillas could remember where food was
hidden 24 hours later.
Schwartz: the gorilla King could remember the order in
which he had been given food items, 5 minutes apart.
(Backwards only!)
Schwartz: the gorilla King could remember which of three
possible events, which had no lasting effect, he had seen up
to 15 minutes earlier.
Menzel: The chimp Panzee could remember the hiding of
food several days later.
Episodic memory – a methodological problem
Did Panzee recall the hiding of food (episodic memory)
or where food lies hidden (semantic memory)?
How could we tell the difference?
Humans are “inferentially promiscuous” (Susan Hurley)
Possible experiment: (1) Prominently show a chimp a key
being placed on a high shelf – this should be a salient
event, but irrelevant (yet) to the chimp’s normal life.
(2) Later, train the chimp to connect the key to the
unlocking of a food cupboard;
(3) one day, appear to have lost the key, and see if the
chimp ‘tells’ you it is on the shelf.
Metacognition
Humans express propositional attitudes to states of
affairs. E.g.
I (don’t) know/believe/think/hope that this is correct.
“When an organism knows what it knows, its actions
are different from an organism that is locked out of its
library of knowledge” (Marc Hauser)
Uncertainty monitoring: Smith and Washburn:
Pigeons and chimpanzees trained to respond `Yes’,
`No’ or `Don’t know’. The ‘Don’t know’ response
typically takes longer than the more certain responses
and is given at the borderline between categories.
Keddy-Hector et al. Piglets backing out of a maze
when they `realize’ they have made a wrong choice.
Animals can represent abstract properties and relations
Alex the parrot.
What colour is this?
RED(x)
Red
COLOUR(RED)
What’s same about these?
Shape.
SQUARE(x), RED(x), PLASTIC(x)
SQUARE(y), BLUE(y), WOOD(y)
SQUARE(z), GREEN(z), GLASS(z)
SHAPE(SQUARE)
Animals can represent abstract properties and relations
Relations between relations
SAME
DIFFERENT
DIFFERENT
DIFFERENT
DIFFERENT
SAME
Animals can do transitive inference
Baboon social hierarchy (3160 possible pairs)
(X dominates Y & Y dominates Z)
X dominates Z
Chickens submit to a chicken who has beaten a
chicken who has beaten them.
Chickens challenge a chicken who was beaten by a
chicken they have beaten.
Lab studies on ordering:
A>B>C
C>D>E
E>F>G
A>G
“The magical number 4” (Nelson Cowan)
Short-term memory is limited to about 4 objects.
Subitizing collections of objects, up to about 4.
Human sentences are limited to about 3
participants (subject, direct object, indirect object).
Watch carefully: how many stars are there?
There is a psychological limit on perceivable
discrete numerosity around 4-5.
Short-term memory
(Nelson Cowan, “The Magical Number 4”)
Many animals can discriminate discrete
numerosities up to about 3-4.
(Stanislas Dehaene, The Number Sense.)
For any language,
the maximum number of obligatory noun phrases
in any sentence (with any verb) is 3.
E.g.
Mary awoke
(1 NP)
Mary ate breakfast
(2 NPs)
Mary put her keys on the table
(3 NPs)
• A limit of four objects in visual working
memory (Luck and Vogel, 1997)
• Mean short-term memory capacity in
adults of 3-5 chunks (Cowan, 2001)
• Deictic subsystems are limited to
about three degrees of difference
(e.g. Japanese ano, kono, sono).
• Minimal subscenes (Arbib) contain up
to about four separate participants.
The basic clauses of languages are
adapted to describing such minimal
subscenes.
Animals (don’t) have propositional
representations of the world
Logically minimal propositions:
x [LION(x)]
There is a lion
E
Many animals have simple predicate-argument
structure.
• The most basic semantic distinction is between
predicates and arguments – PREDICATE (x).
• This asymmetric relation is the first sign of
semantic structure.
• The innermost brackets in any complex semantic
formula are those separating predicates from their
arguments:
believe(john, (E xA y (woman(x) & man(y) & love(x,y))))
Many animals have simple predicate-argument
structure.
A parallel between the predicate-argument
structure PREDICATE(x)
and distinct neural mechanisms for
(i) Attending to an arbitrary object - (x) (via the dorsal stream),
(ii) Categorizing an object - PREDICATE(x) (via the ventral stream).
(z)
RED(z)
Dorsal stream locates object
Ventral stream categorizes object
(x)
(y)
(z)
Posterior
Parietal
Cortex
Pulvinar
Superior
Colliculus
Primary
Visual
Cortex
Lateral
Geniculate
Nucleus
dorsalis
Retina
Inferotemporal
Cortex
(After Milner & Goodale, 1995)
`` ... the most primitive contact that the
visual system makes with the world (the
contact that precedes the encoding of
any sensory properties) is a contact
with what have been termed visual
objects or proto-objects ... As a result of
the deployment of focal attention, it
becomes possible to encode the
various properties of the visual objects,
including their location, color, shape and
so on.'' (Pylyshyn (2000):206)
So, I am committed to one-place predicates as the basis for
representations of scenes/objects/events in animals.
How can at least some scenes/objects/events be represented
solely in terms of one-place predicates?
(More in my talk at 4.00pm.) But here I appeal to two
psychological themes:
• Global versus local attention
• Frame of Reference
Global and local attention
Quick global attention delivers something like
RED
YELLOW
PURPLE
DANCE
GIRL
SKIRT
GIRL
with predicates only approximately bound
Global and local attention
Another example
Quick global attention delivers
KISS
GIRL
BOY
SMILE
Frame of Reference
Judgements are made relative to their contexts.
E.g. What is judged as WHITE in half-light is
judged as GREY in full light.
Jokisch & Troje (2003) Fast-striding animals are
seen as relatively small, and slow-striding animals
are judged to be relatively big.
Sarris (1998) Chickens can be trained to make
perceptual judgements such as ‘big for a red cube’
and ‘small for a green cube’.
An iconic notation,
taking a cue from event semantics
KISS
AGENT
BOY
PATIENT
GIRL
SMILE
Boxes correspond to individual
variables, e, w, x, y, z.
KISS(e)
& AGENT(x) & BOY(x)
& PATIENT(y) & GIRL(y) & SMILE(y)
An iconic notation,
taking a cue from event semantics
AGENT
GIRL
SMILE
Boxes correspond to individual
variables, e, w, x, y, z.
AGENT(y) & GIRL(y) & SMILE(y)
(No ontological distinction between a one-participant event/state
and an individual object.)
Thank you.