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Sunday, September 21, 2014

Mirror mirror in the brain

Lila Gleitman once conjectured that Empiricism, with its associationist commitments, is innate. How else to explain its zombie like capacity to repeatedly come back from intellectual death?  One possible explanation for associationism’s robustness is that it never returns in quite the same form. To paraphrase Mark Twain, Empiricist history never repeats itself, but it often rhymes.  I see this rhyming constantly. Technologically, neural nets were perfectly compatible with Rationalist sentiments (just a matter of initial weightings)[1], nonetheless virtually all of the work done in this framework stank of associationsism.  The same holds, IMO, for lots of recent Bayesian modeling and deep learning.  There is nothing inherent in these approaches that requires a coupling with Empiricist conceptions, but it seems that every computational innovation seems drawn to Empiricism the way flies are to…, well you know.  It seems that we can now add mirror neurons to the list.  Why do I say this? Because I’ve just finished reading a terrific new book by Greg Hickock that critically reviews the mirror neuron literature and its spiritual affinities with Behaviorism. But his book is not merely a debunking (though don’t fret it does do a lot of that) of some bad ideas which quickly became widely influential (another characteristic of Empiricist fads). It is also both a nice accessible report of research on the neuro frontier from a distinguished practitioner, and a nice case study in the philo of science. What follows are some reasons I liked the book and why you might find it worth dipping into.

In case you haven’t heard, mirror neurons are the philosopher’s stones of contemporary neuro-science.  Since their discovery in macaques in the late 1990s in Italy (I don't think macaques are native to Italy, just vacationing there), they have been used to neuronally explain almost everything of cognitive interest from language and its evolution to human empathy and autism.  What are these amazing brain mechanisms?  Well, it seems that they are neurons that fire both when the actor is acting and when the actor is watching someone else act. They are neurons that seem part of both the motor and the conceptual system. Or at least fire both when a monkey is reaching for something and when s/he is watching someone else reaching for something. This has led to a robust version of the motor theory of everything. In other words, understanding is actually re-doing. I understand what reaching cognitively means by simulating the reaching that I see. I understand what I hear by producing what I’ve heard. I understand what someone is feeling, by reproducing the feeling in myself. Talk about walking a mile in someone else’s shoes! That’s the basic idea, and if Greg is right (and I am sure he is) this idea has really caught on.

What Greg does in the book is reveal that this simple idea is, well, at best too simple and at worst, devoid of actual content. The problem is not with the data: there are neurons that do what they have been observed to do. However, the interpretation of what these firings mean has, Greg argues, been deeply over-interpreted; over-interpreted to the point that it is unlikely that much of a claim is being made in most cases. 

All the book is great, but I particularly recommend the sections on the role of anomalies in driving research and the terrific deflationary section on embodied cognition, a notion that really deserves some critical discussion, which Greg more than provides.  I’ve never understood why neuro types thought that embodied cognition could serve as a basis for the “semantics” of action words, but it has. I would recommend reading Greg on this and then, if you still want more, go back and read Fodor and Pylyshyn on compositionality.

 I also recommend you take a careful look at Greg’s discussion of imitation (chapter 8) and its role in “learning.” Here’s a short quote to give you the gist. There is

…a logical error in thinking about imitation as the foundation for more complex capacities like theory of mind, or that imitation itself had to evolve to unleash a great leap forward. Maybe we should think the other way around. Imitation is not the cause but the consequence of the evolution of human cognitive abilities…(200)
And

For imitation to be at all useful, you have to know what and when to imitate and you have to have the mental machinery behind imitative behavior to put it to good use…More specifically, to understand the role of imitation in language learning, we need to study how language works…Or to frame it a bit differently, rather than centering our theoretical efforts on imitation and then seeing what computational tasks imitation might be useful for, we might center our focus on particular computational tasks (language, understanding actions, grasping for objects) and then see what role imitation may play…(201).

Imitation is a current refuge for associationist theories of learning. And mirror neurons are the latest neuronal candidate for the grounding of associationism.  Greg’s critical discussion, IMO, effectively blows up this bankrupt train of theorizing. I’m not surprised, but I am grateful. Someone’s got to clean out the Augean stables and Greg is very effective with a shovel.

Here’s another quote making the all too common link to associationsism (228):

We’ve been down a similar road before. Behaviorists had very simple mechanisms (association and reinforcement) for explaining complex human behavior. But removing the mind as a mediator between the environment and behavior ultimately didn’t have the required explanatory oomph. Mirror neuron resonance theory isn’t quite behaviorism, but there are not many degrees of separation because “it stresses… the primacy of a “direct matching” between the observation and the execution of an action.” The notion of “direct matching” removes the sort of operations that might normally be thought to mediate the relation between observation and action systems…The consequence of such a move is loss of explanatory power. The mirror neuron direct matching claim results ina  failure to explain how mirror neurons know when to mirror in the first place. We then have to look to the “cognitive system” for an explanation, which lands us back where we started: with a complex mind behind the mirror neuron curtain of explanation of complex mental functions.

As Greg notes, his critique of mirror neurons is a modern revamping of Chomsky’s critique of Skinnerian behaviorism. Where it’s clear, it’s clearly false and where it seems true it borders on the truistic and vapid. 

There is lots more in the book. For neophytes (e.g. me) there is a good discussion of the dorsal and ventral systems of brain organization (the how vs what organization of brains that Greg and David Peoppel did so much to make part of the contemporary common neural wisdom in the domain of language), and the various kinds of techniques that modern neuro types use to probe brain structure.  In addition, there are lots of great examples that signal to the careful reader that Greg is clearly a pretty good surfer and that he loves dogs. 

So, if you are looking for a good popular neuro book or just a good debunking, Greg’s book is a great place to go. Would make a marvelous Rosh Hashanna present or a great Yom Kippur stocking stuffer.



[1] As Rumelhart and Maclelland noted in their fat initial volumes (here).

12 comments:

  1. So the message is that imitation involves a lot of complex cognitive infrastructure? This would not be a surprise, since the ability to learn by imitation is extremely useful, and the infrastructure would have had a reasonably long time to develop.

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  2. You are certainly correct, Avery. The infrastructure is complex and much of the mirror neuron hype in the media was just that - hype [who knew?!]. However, a hyped book to battle hype seems hardly the best response strategy. One friend of mine who actually works on mirror neurons put it much better than I could: "What disturbs me is the glee with which so many people want to destroy mirror neurons rather than help us progress to a more subtle understanding of their role."

    Especially hard to understand is Norbert's glee given that even if it were the case that everything ever claimed about the role of mirror neurons is false, that would be of zero help to him when attempting to give a positive account of the biological implementation of whatever it is that remains domain-specifically innate on MP assumptions...

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  3. Norbert isn't a neuroscientist, nor should be be, either.

    I believe the issue with the mirror neuron folks is that they claim large swaths of cognition to their purview and demand all attention to a small class of cells. Hickok has rightly incorporated these findings into a larger, integrated theory of cognition. I agree that perhaps too much time is spent debunking the claims, but at least the debunking is done in service of an alternative and inclusive framework for how things work.

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  4. Genuine question: Does the book criticize associationism at all? Because imitation is something quite different, and I always thought that associationism (e.g. LTP) is uncontroversial in neuroscience.

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    1. Genuine answer: i do not know whether the book does. It is certainly true that some claims about mirror neurons were incorrect and/or overblown. For a recent criticism have a look at this 2014 BBS paper and the commentaries:
      http://www.all-souls.ox.ac.uk/users/heyesc/Celia's%20pdfs/9%202014%20Cook%20et%20al%20BBS.pdf

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    2. I agree with a lot of the criticisms of mirror neurons (and read the blog that GH cowrites) -- http://www.talkingbrains.org/. It's worth subscribing to it.

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    3. The great Randy Gallistel has a review article on LTP arguing that it doesn't do what it advertises and the reason it is still so widely assumed to be the basic learning mechanism is, you guessed it, a lingering empirically unsupported associationist prejudice in the neurosciences. The paper is here:
      http://ruccs.rutgers.edu/~galliste/images/publications/GallistelBalsamLngMemory2014.pdf
      As I tend to believe almost everything Randy writes, I find this article compelling as well. Associationsim is everywhere. It is a plague and a scourge in the cognitive and neuro sciences. When examined carefully, it always proves to be inadequate. It would be great to see it disappear except as maybe a dead horse worth occasional beating.

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    4. Does the book criticize associationism at all?

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    5. Insofar as behaviorism is a species of associationist and insofar as I itation is a favored mechanism for forming associations.

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  5. It seems to me that wholesale rejection of association risks loss of the infant. Association is an integral part of the meanings of words in the form of world knowledge (encyclopedic meaning). I wonder if it isn’t also integral to Merge, with its dependence on feature-checking. So far as non-syntactic, semantic features are concerned a form of association appears to be required as a mechanism to determine the compatibility of the words to be merged in a specific context.

    I haven’t read the book but Hickock’s quoted criticism of imitation theory sounds dubious. IMO much of the value of mechanical imitation lies in its capacity to transmute into miming and then intentional action once an imitated action is found to work. A good example of embodied cognition. No, I am not an associationist. I believe the innate semantic factors that I have talked about in other posts are central to cognition and behaviour.

    The pervasiveness of association (not associationism) in the thinking of neuroscientists is hardly surprising as it seems to describe much of the motivation of activity in the brain’s ‘innernet’, its directed neural activity.

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  6. Is there a way to distinguish "powerfully simple" ideas from facile ones? I feel like after a long day of doing real work, associationism and imitationism seem like creation myths. But charitable and skeptical people (like me even) often want to stop to give ideas like this a second chance because "if it works it could be great"; or "because of Darwin's problem."

    There must be a reliable technique for demonstrating that, in fact, the cloak of reasonableness around some facile idea is nothing more than a post-hoc justification for "it works the way a five year old would say it does."

    There ought to be a simple way of reinforcing that science seeks counter-intuitiveness first (or, lack of respect for intuitiveness) and simplicity second.

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    1. I think more relevant in this case is the fact that this "simple" idea has had a long shelf life and is way past its sell date. There is a body of criticism gong back about 250 years that one hopes would serve as a kind of test bed if revival were being considered. What's so amazing about the empiricism/associationist myth is not that it keeps recurring, but that it keeps recurring in more or less the same way every time. In the domain of language, we have what Chomsky in another context dubbed "a body of doctrine." If one is interested in reviving an old idea here's a suggestion: take aim at some of these results and explain them. This, IMO, should be the ticket for admission to serious discussion. Or, find another relevant body of doctrine that the old ideas can explain and the new ones cannot. The problem is that more often than not, the "simple" ideas that have proven failures are not expected to meet regular standards. IT appears that this was also true of mirror neurons, if Greg is right. So, is there a reliable technique? Not if you mean an infallible one. But there is a pretty good one that we all are taught to use but it seems that some ideas are exempt from having to meet.

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