Episodic-like Memory and other Behavior in Scrub Jays

1. Episodic-like Memory and other Behavior in Scrub Jays Lecture 7 Psych 1090

2. I’ve done things a bit differently in this lecture… assigning only a review paper for the earlier material and giving the details in the lecture

3. What is episodic memory? • unique, personal, past experience • recalled in terms of a time frame or temporal-spatial relation • thus tells ‘what’, ‘when’, and ‘where’ • not expected in nonhumans

4. Explanation in terms of other forms of human memory: • Procedural memory • inaccessible to conscious recall • examples are some motor skills, or simple classical (Pavlovian) conditioning • Declarative memory • involves propositional material, symbols • used to guide inference, reasoning, true/false statements

5. Declarative memory is subdivided: • semantic memory • factual knowledge of the world • what one knows from books, etc. • episodic memory • factual knowledge of past experience • what one knows from living one’s own life

6. According to Tulving and Marlowitsch, episodic memory is • unique to each episode • allows recall of past experiences rather than facts • develops later in children; is impaired faster in age than semantic memory • related to unique cortical activity

7. Supposedly, animals remember facts (semantic memory) but not personal experiences (episodic memory) plenty of evidence to show that animals remember that ‘x indicates y’, or ‘if x, do y”, but not necessarily ‘when I saw x, I then remember doing y’

8. The point may seem trivial, but it’s not.. The difference is in knowledge that is assumed to represent the way the world works for everyone (semantic memory) And knowledge that is understood to represent only what one has personally experienced (episodic memory)

9. Which brings up another issue: Some researchers argue that to understand that an experience is personal, a being must have full consciousness…. an attribute that is generally denied to animals.

10. To get around the argument that a being must be conscious in order to have personal memories—i.e., to have episodic memory—we can simply agree to define episodic-like memory as retrieval of “what”, “where” AND “when”

11. Thus the issue of personalization and of self-projecting past to future And of assuming that others experience life similarly Such a definition puts emphasis on the ‘episode’ aspect of episodic memory, and is one that can be tested in animals

12. Note that other types of memory that have been studied may seem to involve time, but are not truly episodic…. For example, animals trained on delayed match-to-sample or delayed nonmatch-to-sample may seem to be recalling previous, personal events….

13. That is, being shown a red sample at time T and then, at T+20 seconds, being shown red and green samples, they have learned—via trial and error—that they get rewarded only for matching or not matching the original sample shown at time T

14. One could argue that the animals are responding based on personal, event-based memories….. They may, however, simply be choosing or avoiding the most familiar object…. Which really has nothing to do with ‘episodes’

15. Specifically…. There is a distinct difference between • recognizing something as ‘familiar’ and • a specific recollection of where and when it has been seen before

16. Another example…. The difference between knowing a face is familiar and remembering that you saw this person last Saturday night at the bar in Harvard Square

17. But many animals likely demonstrate some kind of episodic memory in nature…. Nest parasites, like cuckoos, must keep track of the location and state of nest-building and egg laying in their hosts so as to know when to drop their eggs

18. And because recently researchers found that cuckoos will destroy the nests of hosts who dump their eggs… Some connections might be made in terms of personal experience for both hosts and cuckoos…

19. But probably the best example are food-caching birds… As we learned last lecture They store thousands of food items in the autumn in thousands of locations, and recover them over the course of several winter months

20. And even though the scrub jays that are used by Clayton et al. don’t cache nearly as much as the nutcrackers and pinyon jays they do cache some food, and for times a bit longer than chickadees

21. To connect to episodic memory: • information guiding recovery is based on a single, past, personal memory • retrieval requires precise spatial data • birds need to remember the order of caching to prevent spoilage • birds need to remember precisely what was stored in which cache to prevent spoilage

22. To get clear data on such behavior, Clayton and Dickinson performed a series of experiments with scrub jays Birds were allowed to cache wax-worms (perishable and preferred) and peanuts (non-perishable and liked) in visually distinct sites in the laboratory Sites were ice cube trays with Lego blocks in varied patterns…

24. Birds were divided into two groups, Degrade and Replenish Birds in the “Degrade” group were given the chance to cache peanuts and wax worms in two different trays and then recover at both 4 hours and 124 hours, and to learn that the worms would be horrid after 124 hours

25. They then were tested by being allowed to cache and recover the two different foods at the two intervals But now the experimenters removed all the food items before recovery, so birds couldn’t possible smell the degraded worms….

26. The researchers found that after 4 hours, the birds preferred to visit the sites where they had cached the worms… but went to the peanut sites after 124 hours suggesting that they knew precisely what was where and the time delay

27. But maybe the birds just remembered which caches they had already emptied… Or maybe they just more rapidly forgot worm sites… i.e., maybe some evolutionary rather than memory process was at work…

28. So the researchers worked with the Replenish group who never learned that the worms degraded because the researchers put in fresh ones before allowing recovery at 124 hours

29. When tested with all food removed, these birds preferentially went to the worm sites, at both 4 and 124 hours Thus the behavior of prioritizing which food to recover was learned, and not some genetic instinct… And was nice preliminary evidence of episodic-like memory

30. But this design still didn’t examine whether the birds in “Degrade” understood more than “time makes worms decay” …i.e., just that something about the time at which they stored the various foods was important

31. So now the birds could store both foods (nuts and worms) in one tray at one time then a few days later could again store both foods in another tray and after a short interval after the last caching, were allowed to recover

32. So, in order to get worms and nuts appropriately (avoid yucky worms) they had to remember which tray was cached when And not just better memory for nicer food And they succeeded on that task

33. To tease this out even further, the researchers designed another experiment in which the birds got to store the different foods at different times, and then recover them at the same later time

34. Birds were thus allowed to cache one type of food in one side of the tray at first • were made to wait 120 hours • and then were allowed to cache the other type of food in the other side of the tray…. • the type of food altered with respect to time in two different sets of trials

35. Test: predict worms Peanut, then Worm P W P W 120 h 4 h Worm, then Peanut Test: predict nuts W P P dW 120 h 4 h

36. Birds with experience with degraded worms chose worms at a significantly higher rate than peanuts when the worms were cached last and peanuts at over twice the rate when the worms were cached early and likely degraded

37. Interestingly….and critically….birds with no experience with degraded worms chose the worms in both cases— that is, they just chose on preference not as to what was likely to have happened to the worms

38. Thus: • The peanut-side preference shown by the Degrade group was not simply due to differential forgetting of worm caches • the preference to search for worms 4 hrs after caching and peanuts 120 hrs after caching does not reflect a genetic predisposition, because it was learned

39. But what if the birds were trained on something totally counter-intuitive…. That worms were yuckky after a couple of hours But somehow were ok after a few days?

40. Test: predict nuts Peanut, then Worm dW dW P P 120 h 4 h Worm, then Peanut Test: predict worm W P P W 120 h 4 h

41. And the birds acted as predicted functioning on the basis of what they had learned about worms And it wasn’t what they learned during the test phase because they acted OK from trial 1

42. Moreover, the birds’ behavior was not just a matter of familiarity of the tray that is, somehow associating tray with the issues because the tray exposure was the same for each type of caching

43. The switch by the birds in the Degrade group requires the birds to recognize a particular cache site in terms of both its content and the relative time that has elapsed between caching and recovery

44. The birds HAD to recall information about • what (worms vs. peanuts) was cached • where it was cached (right vs. left) • when (4 hrs vs. 120 hrs)

45. Too…the information was acquired on the basis of a single, trial-unique personal experience That is….something getting quite close to episodic memory

46. Note the result cannot be explained by the simple rule “search the side of the tray in which food was stored most recently, regardless of food type”…. birds couldn’t use recency, because each food was cached at the same time in different trials

47. Researchers next wanted to make sure that the birds remembered not only which sites have been depleted (data from experiments by Kamil and Balda that we discussed) but also exactly WHAT was recovered

48. not just the choice of spoiled vs. unspoiled, but also what might be more appealing at a particular time…. which relies on a very personal memory for what has been consumed recently not just always go for “X” if it’s fresh

49. So, they tested whether what they fed the birds just prior to recovery would affect what they recovered…. and also made them remember where the different foods were stored in two different trays…. The trials are quite complicated!

50. (1) cache P in one side of each tray (3) 3 hrs later, allowed to recover P from one tray and K from the other A P A P / K B P P / K B A few mn (2) cache K in one side of each tray (4) Prefeed bird P, see what it does A P K / P K A B P K B P / K