Mixing Memory

Got your attention, right? That’s the title of a paper by Penn, Holyoak, and Povinelli in April’s Behavioral and Brain Sciences. Well, the full title is “Darwin’s mistake: Explaining the discontinuity between human and nonhuman minds.” Here’s the abstract:

Over the last quarter century, the dominant tendency in comparative cognitive psychology has been to emphasize the similarities between human and nonhuman minds and to downplay the differences as “one of degree and not of kind” (Darwin 1871). In the present target article, we argue that Darwin was mistaken: the profound biological continuity between human and nonhuman animals masks an equally profound discontinuity between human and nonhuman minds. To wit, there is a significant discontinuity in the degree to which human and nonhuman animals are able to approximate the higher-order, systematic, relational capabilities of a physical symbol system (PSS) (Newell 1980). We show that this symbolic-relational discontinuity pervades nearly every domain of cognition and runs much deeper than even the spectacular scaffolding provided by language or culture alone can explain. We propose a representational-level specification as to where human and nonhuman animals’ abilities to approximate a PSS are similar and where they differ. We conclude by suggesting that recent symbolic-connectionist models of cognition shed new light on the mechanisms that underlie the gap between human and nonhuman minds.

In short, Penn et al. argue that relational reasoning abilities separate the mental capabilities of humans and other animals. It’s an interesting read, particularly for those of you who are interested in the evolution of human cognition. If you have a subscription (and maybe if you don’t — I never know with BBS), you can read the entire article, along with all of the peer commentaries, and the authors’ response to them, here. Some of the commentaries are pretty good, especially the one by yours truly (I kid). If you can guess which one, I’ll give you a cookie, and an immediate comment deletion (gotta preserve the anonymity, ya know?). Might be better to guess in an email, now that I think about it.

Anyway, if you don’t have a subscription, you can read the full article here for free, but unfortunately, you can’t read any of the commentary, and with BBS articles, seeing a bunch of people strain to make their own work relevant to the target article (myself included) is at least half of the fun.

Feel free to discuss the article in the comments here. Should make for some interesting conversation.

Comments

#1 Brandon
May 19, 2008

Well, it doesn’t have much to do with the cog. sci. of it, but as I’m always wary of what people attribute to Darwin, here’s more of the passage in which Darwin makes the ‘mistake’ (to keep the quotation from being even more absurdly long for a comment than it is, I’ve taken out some elaboration, but that’s it):

There can be no doubt that the difference between the mind of the lowest man and that of the highest animal is immense. An anthropomorphous ape, if he could take a dispassionate view of his own case, would admit that though he could form an artful plan to plunder a garden?though he could use stones for fighting or for breaking open nuts, yet that the thought of fashioning a stone into a tool was quite beyond his scope. Still less, as he would admit, could he follow out a train of metaphysical reasoning, or solve a mathematical problem, or reflect on God, or admire a grand natural scene….

Nevertheless the difference in mind between man and the higher animals, great as it is, is certainly one of degree and not of kind….If it be maintained that certain powers, such as self-consciousness, abstraction, &c., are peculiar to man, it may well be that these are the incidental results of other highly-advanced intellectual faculties; and these again are mainly the result of the continued use of a highly developed language.

Thus Darwin’s view is not that there is no discontinuity between human beings and other animals, but that any discontinuity is (probably) explicable by the particular way in which high-level cognitive abilities happen to combine in humans, where each ability considered singly is a more advanced kind of an ability shared with other animals.
#2 Derek James
May 19, 2008

Ah, cool. I just finished this article a couple of days ago. I took a course on the evolution of primate cognition with Povinelli this last semester and many of the topics mentioned in the paper came up.

Over and over I was struck at how little we can actually infer from experiments on animal cognition, but how readily experimenters tended to read too much into the results. I think it’s fascinating trying to devise clever experiments to try to get at some of these issues, though all in all I’m glad I’m doing computational modeling instead.

I think the actual argument of degree vs. kind is ultimately not very interesting (kind of like the nature vs. nurture debate), but the review of the various literature on animal cognition is extremely interesting. And the discussion of the relevance of the Physical Symbol System (PSS) hypothesis to the issue is also very interesting.

I’m especially interested in what people might think about the appendix, which proposes experimental designs which the authors suggest should provide more insight into some of the issues discussed in the paper than the studies they reviewed.
#3 razib
May 20, 2008

i can’t believe you dissed the big-D! never shall i peruse the contents of this web-publication in the future!
#4 Susan
May 20, 2008

You had better be careful, I see this blog popping up on creationists sites. No only for suggesting that Darwin was wrong, but that there is such a “profound discontinuity between human and nonhuman minds.” Why would this discontinuity exist? A higher power perhaps…Some intelligent designer perchance? I do agree however, I’ve always wondered about the distance between the minds of humans and other creatures. Over the years I’ve seen documentaries on animal intelligence (Especially apes) and I have never been impressed with the observations. It always seemed to me that researchers have been blinded by affection for their subjects of study and were reading more into the results then they should have. I’ve been bothered by the lack of some “halfway creature” some animal that was on the way to achieving human-like sentience. Why isn’t there the existence of such an animal? Is it because the chain of conscienceness that led to modern humans, our ancestors that began to seperate us from the apes, is extinct? We have trouble seeing how we crossed the chasam because the bridge has washed out? Or is it because we are so biased by our own great intelligence that we only look for “human” intelligence markers in other animals? Maybe there are other ways to be intelligent that we haven’t comprehended yet.
#5 ceresina
May 20, 2008

Are you co-author with someone who thanked Tiki Barber in his acknowledgments once?
#6 Chris
May 20, 2008

Derek, I agree, in these sorts of discussions, we’re on shaky ground. The problem of comparing cognitive abilities across species is incredibly complex, because whatever cognitive abilities we share, or don’t share, will serve different practical ends, be realized in different behaviors, etc. But I do like the idea of developing hypotheses and going out and testing them, rather than simply stabbing in the dark, and I am particularly fond of this hypothesis for various reasons. I hope Penn, Povinelli, and others work hard to rigorously test it.

Susan, that’s funny, ’cause if they read the paper, what they’ll find is that the authors are hypothesizing a relatively small (functionally) — just the sort of difference you would expect to occur through evolution — underlies the vast behavioral differences we observe between species. Poor creationists.

ceresina, I’m impressed!
#7 Michael
May 20, 2008

I think more blogs should link to this article or to blogs who discuss it, so that the first google hit for “Darwin’s Mistake” isn’t some murky book that claims that “Antediluvian Discoveries Prove Dinosaurs and Humans Co-Existed” anymore.
I haven’t read the whole article yet, but I think Penn et al. do a good job in looking for the most parsimonious explanations of nonhuman animals’ behavior. But I wonder if this doesn’t also weaken their case for an unparsimounius, supermodular, higher-order releational reasoning capacity, because it also follows from their reasoning that human capacities should be examined under the same light.
#8 Michael
May 20, 2008

I think more blogs should link to this article or to blogs who discuss it, so that the first google hit for “Darwin’s Mistake” isn’t some murky book that claims that “Antediluvian Discoveries Prove Dinosaurs and Humans Co-Existed” anymore.
I haven’t read the whole article yet, but I think Penn et al. do a good job in looking for the most parsimonious explanations of nonhuman animals’ behavior. But I wonder if this doesn’t also weaken their case for an unparsimounius, supermodular, higher-order releational reasoning capacity, because it also follows from their reasoning that human capacities should be examined under the same light.
#9 RBH
May 20, 2008

I commend John Wilkins’ take to your attention, particularly his remarks on the footnote in which the authors essentially disclaim their title. Their footnote is particularly interesting in the light of the extended quotation from Darwin above.
#10 Michael
May 22, 2008

I’m not sure but I think I encountered some kind of logical fallacy in the article.
Maybe I’m confusing things but Penn et al. write that human cogntion isn’t a Physical Symbolic System per se, but instead “human subjects are often able to approximate the systematic, higher-order, relational capabilities putatively associated with a PSS” (Penn et al. 2007: 124),
This is then called the “Symbolic Approximation” Hypothesis. After having clarified that human cognition only approximates A PSS they go on to say that:
“Unlike the PSS hypothesis, however, the Symbolic Approximation hypothesis invites the possibility that different cognitive organisms may approximate different features of a PSS to varying degrees or even, [...] in a punctate and content-specific manner. And, in fact, this is exactly what the comparative evidence suggests is the case” (Penn et al. 2007: 124).

So in fact what they say is that,
1. There is a CONTINUUM of a cognitive apparatus more or less approximating a PSS
2. This CONTINUUM ranges from an extremely low approximation to a PSS to a fairly close approximations
3. On this gradient CONTINUUM, nonhuman animals are pretty close at the No-PSS pole, and Humans are pretty much at the PSS pole.

But if there are only degrees of approximation on a gradient ranging from something not much resembling a PSS to something approximately resembling a PSS, how can there be a DISCONTINUITY between human and nonhuman minds?
#11 windy
May 27, 2008

I’ve been bothered by the lack of some “halfway creature” some animal that was on the way to achieving human-like sentience. Why isn’t there the existence of such an animal?

Maybe there was, but we ated it.
#12 Ricky
May 28, 2008

Where is Sue Savage-Rumbaugh’s categorization work with the chimpanzees Sherman and Austin?
#13 GNZ
May 30, 2008

When doing research on animal inteligence we generally take the basic assumption that “if it is not proven than an animal can do somthing it is reasonable to assume they can’t.”

this is obviously flawed (although probably better than the opposite) so it creates a fertile ground for research regarding studies that demonstrate that animals do have some trait or other. With a little work we can get such research into magazines and the news.

—–

If there was a halfway creature we would probably eat it. There is only one niche available for an organism of the intellience of man and we have it already.

Maybe that is related to how under our stewardship animals like rats and rabits proliferate while chimps large cats whales and so forth approach extinction.