Episodic Memory in Animals

1
Episodic Memory in Animals

• Episodic memory is the form of memory that
  allows an individual to recollect happenings from
  his or her past. (Tulving, 1992)?
• ---gt Do animals have Episodic Memory?

2
Tulving's view
According to Tulving, animals like his cat have
no episodic memory so while they may know many
things, they do not remember past experiences the
way we do. They just know about them. (Drawing by
Ruth Tulving)
http//www.science.ca/scientists/scientistprofile.
php?pID20
3
Semantic and Episodic Memory

• According to Tulving and Markowitsch (1998), the
  relation between Declarative/ Semantic and
  Episodic Memory is one of inclusion while you
  can have sem M without EM, you cannot have EM
  without sem M.

4
What is special about EM?

• 1. conscious recollection of past experiences
• 2. At the moment of retrieval, oriented to the
  past
• 3. Accompanied by autonoetic consciousness,
  allowing for 'Remembering' instead of 'Knowing'
• 4. Embedded relationship EM ? sem M
• 5. EM develops later in children than sem M
• 6. EM is more vulnerable (amnesia, aging)?
• 7. EM is dependent on PFC, according to Tulving
  on the hippocampus
• 8. Unique to humans?

5
Consciousness in animals?

• Especially the properties that relate to
  conscious experience of recollection of past
  episodes are an unsurmountable obstacle for the
  attribution of EM to animals since there are no
  agreed behavioral markers of conscious recall in
  animals.

6
The 'what', 'when', and 'where' of an episode

• Studying EM in animals becomes more tractable
  when the 'old' definition of EM (Tulving, 1972)
  is applied
• EM is the retrieval of informtion about 'where'
  a unique event or episode took place, 'what'
  occurred during the episode, and 'when' the
  episode happened.
• These spatio-temporal properties of EM can be
  demonstrated in the behavior of animals.

7
Alternative explanations of animals' behavior,
example

• Animals have EM
• Rats remember where the hidden platform in the
  water is and swim to this platform on the next
  occasion

• Animals have decl M
• Rats have acquired knowledge about where in the
  water the platform is and approach the most
  familiar location without recollecting the
  episode when they had been there before

8
General problem superset-subset relation

• Since sem. M is a proper subset of EM, sem. M is
  sufficient to explain the animals' behavior, and
  since there is no way to prove that animals have
  EM (or consciousness), the most parsimonious
  explanation is that animals solve the problem
  with sem. M.
• Episodic Memory
• Semantic Memory

9
Arguments for EM in food caching birds (here
scrub jay)

• 1. The recollection relates to a single past
  episode
• 2. The recollection is accurate and specific
• 'when' and 'where'?
• 3. Birds even remember 'what' they have cached
• -gt it is an adaptive advantage for birds to
  remember, where, when, and what they have cached,
  so EM is evolutionary favored.

10
Experimental paradigm(Clayton and Dickinson
1998)?

• Independent variables
• 1. When Time 1 (4 h later), Time 2 (120 h
  later)?
• 2. Where Location 1, Location 2 (two adjacent
  sites)?
• 3. What perishable Worms W non-perish. Peanuts
  P
• Dependent varible number of searches for P and W

Pre-experimental manipulations 'Degrade' G-
Group Has learned that the favored worms decay
after 120 h, so will not search for
them 'Replenish' R-Group Has learned that worms
are still fresh (since replenished) after 120 h,
so will search for them since they prefer worms
over peanuts
11
Experimental paradigm(Clayton and Dickinson
1998)?

• Peanut/Worm PW trial
• 1. Peanut is cached in Location L1
• 2. 120 h later Worm is cached in Location L2
• 3. 4 h later where will scrub search?
• Worm/Peanut WP trial
• 1. Worms are cached in L1
• 2. 120 h later Peanuts are cached in L2
• 3. 4 h later where will scrub search?

12
Hypotheses

• Degrade Group
• Will search for Worms only in P/W trials, since 4
  h after caching W are still fresh
• Will NOT search for worms in W/P trials, since
  124 h later W will have perished

• Replenish Group
• Will search for Worms on both P/W and W/P trials
  since, in their experience, Worms are still
  fresh at 124 h

13
Results
P/W trial

• Hypotheses are borne out
• D group,P/W trialW gt P
• R group,P/W trial W gt P
• D group, W/P trial P gt W
• R group, W/P trial W gt P

W/P trial
14
Discussion

• The results cannot be explained by
• Differential forgetting of Worms and Peanuts
• Genetic predisposition to prefer worms, but by
  strategy after learning
• Crucially, the W/P preference was reversed for
  the D and the R group after having cached worms
  for the long interval only R-birds would recover
  them, not D birds
• This requires recall of the following
  information
• 'what'(worms vs. Peanuts
• 'where' Location 1 vs. 2
• 'when' short vs. long interval
• This can hardly be explained by familiarity (sem.
  M) alone.

15
EM (humans) and E-like M (animals)?

• Birds show the hallmarks of EM, except conscious
  recollection.
• It is this feature that presently makes
  'episodic' memory a unique human phenomenon, and
  probably always will. (Griffiths et al., 1998,
  79)?
• According to Tulving and Markowitsch (1998), it
  is impossible to prove the absence of EM in
  animals, since a universal negative cannot be
  disproven.
• The best one can do is to attribute
  Episodic-like Memory to them.
• E-like M in animals in an analogue in the animal
  kingdom of EM which is reserved for humans.

16
On a less strict reading the only real difference
between men and birds is...
17
References

• Clayton, N.S., and Dickinson, A.D. (1998)
  Episodic-like memory during cache recovery by
  scrub jays. Nature, 395, 272-274.
• Griffiths, D., Dickinson, A., and Clayton, N.
  (1999) Episodic memory what can animals
  remember about their past? Trends in Cognitive
  Sciences, 3, 74-80.
• Tulving, Endel (1972) Episodic and semantic
  memory. In Endel Tulving and W. Donaldson (Eds.),
  Organisation of memory. Academic Press, 381-403.
• Tulving, Endel (1992) Episodic memory. In Larry
  Squire (Ed.), Encyclopedia of learning and
  memory. NY Macmillan Press, 161-163.
• Tulving, Endel, and Markowitsch, J. Hans (1998)
  Episodic and Declarative Memory Role of the
  Hippocampus. Hippocampus, 9, 198-204.
• Tulving, Endel (2002) Episodic memory from mind
  to brain. Ann. Rev. Psachol, 53, 1-25.