Week 7

The topic this week is sequential behaviors and ordinal knowledge. Notably, this is quite relevant to some of the topics we discussed before, particularly timing and counting. The serial learning paradigms reviewed in chapter 31 and 32, which presented sequential patterns to rats, seemed to be a paradigm developed based on the earlier paradigms that studied animal perception of time. For example, here the animals need to be able to discriminate and memorize stimuli occured at different times. Thus the paradigms here probably rely on rats’ ability of timing and counting, as well as other additional abilities such as memory. Therefore it seems natural that researchers found multiple cognitive processes and brain areas (basial ganglia, caudate nucleus, hippocampus, etc.) supporting sequential learning. Additionally, spatial navigation also seems to be an ability based on sequential learning, since it requires humans/animals to carry out a series of actions based on spatial cues.

In chapter 31, authors first discussed a series of experiments using a circular 8-lever (1-8) chamber with rats. They found that rats were able to extract abstract rules in behavioral patterns, including hierarchical patterns (e.g., 121 232 343…) and interleaved patterns (e.g., 182838…). It was particularly impressive that rats were also able to learn a pattern interleaved with another alternating pattern (e.g., 17283748…).

The next part discussed phrasing cues, which was somewhat confusing to me. It was quite unclear what the “cues” refer to (for example the authors said “spatial or temporal cues were placed congruent with boundaries between subpatterns”, and I’m not sure what that means, particularly the spatial cues as the patterns seemed to be temporal). But it seems like the cues (such as time interval between chunks) helped rats highlight the patterns and thus facilitated their learning. This reminds me of a personal experience relevant to chunking: I was given a door code as 331-1321, and constantly forgot it until I started to regroup it as 3311-321, which, according to this paper, can be seen as a hierarchical pattern with different subpatterns. I wonder if rats also have the ability to regroup the “incorrectly” grouped patterns.

The authors did more experiments on pattern violation to examine the factors contributing to rats’ pattern learning. In particular, rats by default seemed to rely on spatial location of the levers to remember the serial actions, rather than the position of the action in the action series. However, they were also able to learn the serial position of the violations with great difficulty. Rats also learned “runs”-phrased patterns (e.g., 1234 3456 …) more quickly than “trills”-phrased patterns (e.g., 1212 3434), which was similar to humans. I wonder if this is because the runs-phrased pattern can be seen as fewer sub-patterns than trills-phrased pattern, so they actually require less working memory. For example, you could see the runs-phrased pattern as a series of 4-digit consecutive sequences, so each 4 digits can be seen as one chunk; but for the trill-phrased pattern, it’s a series of repeated 2-digit sequences, and each 4 digits have to be separated into two chunks, so there are more chunks to memorize and thus more difficult.

In chapter 32, some of the experiment employed a spatial navigation (maze learning) paradigm to study sequential behaviors. Here, the authors discussed the possibility that rats formed a cognitive map as the spatial representation of relationships. This is actually quite relevant to what I talked about at the beginning of my blog last week, that we may process abstract relations (such as semantic concepts or social relations) as if they were spatial relations. In fact, perhaps brains could just process any type of relation in the same way for efficiency purposes, including the relations between items in sequences.

Chapter 32 also described a really interesting study comparing monkeys and pigeons, and found that for a sequence ABCDE, pigeons really learned a few rules (e.g., “respond first to A”, “respond last to E”), unlike monkeys (or us) who learned the consecutive relations between all 5 items. I wonder if this behavioral pattern of learning “if-then” rules also apply to other birds and not other primates, or if this just happens to be a non-generalizable difference between pigeons and specific primates. Additionally, I am certain that if-then rules are way easier for robots than other types of relations, since it is the most basic function of any programming languages. Just because of how basic it is, are the other types of relations we know, such as sequential or even bidirectional relations, just variants of if-then rules, or do our brains represent if-then relations and other types of relations in fundamentally different ways?

The author further showed that monkeys were able to learn not only the sequential relations between stimuli, but also the abstract concepts of numbers in terms of their relative magnitudes and the different distance between numbers. This is again connected back to the counting topic a few weeks ago. Furthermore, researchers found that the firing rate of single neurons in monkeys’ IPS encoded the magnitudes of numbers, and that the width of their tuning curves increased logarithmically with the magnitude, conforming to Weber’s law. The increased width of tuning curves could also account for the fact that primates are better at discriminating smaller numbers than larger ones. The discussions in this chapter on numerical representations are very interesting, and I wonder how it may or may not be relevant to sequential learning. As the author suggested, when learning sequential stimuli, monkeys and us actually learned the sequential relations between the stimuli, unlike pigeons who learned more about the if-then rules. Does that mean we are associating each stimulus with an ordinal position in the sequence, and could that be a necessary ability to have before developing the cognition for actual numbers and magnitudes?

These two chapters really left me with a lot of questions that I wish could be answered with more research…