topics: |  brain | memory | language | evolution

Well written guide through cognition

Why does a face look more attractive with makeup?

Partly, the answer has to do with how the brain reconstructs a 3D world from
its retinal images, which are essentially 2D and could have been created by
an infinite number pf possible worlds.

 
For example, these two seem images of cardboards folded horizontally (left)
and vertically (right).  Yet all the squares are identically coloured, and
the image edges marked 1 and 2

	are physically the same in the two drawings. But in the left drawing
	the border looks like a paint boundary — a white stripe next to a gray
	one—and in the right drawing it looks like a shape-and-shading
	boundary—a white stripe falling into a shadow on the other side of a
	fold. The borders labeled "2" are also identical, but you see them
	[differently]. p. 243

The answer has to do with the fact that the probability that these are images
of 3D objects of the type you see, are higher than any other hypothesis your
brain can construct.

So on to makeup.  The answer relates to the shape-from-shading function, one
of the components for viewing a scene as 3D.  The angle of a surface results
in it being shaded differently; we use the shades to infer
(probabilistically) the angle of surfaces.  When makeup changes the shade, we
feel the surfaces may be differently inclined:

   pigment on the skin can fool the beholder into seeing the flesh and bone
   as having a more ideal shape. Dark blush on the sides of the nose makes
   them look as if they are at a shallower angle to the light, which makes
   the nose appear narrower. White powder on the upper lip works the other
   way: the lip seems to intercept the light source head-on as if it were.
   Fuller, bestowing that desirable pouty look.  p. 249

Of course, this is only part of the story...

Review by Jerry Fodor

The Trouble with Psychological Darwinism, Jan 98,
London Review of Books

    [This review opposes the non-logical, evolutionary position.  In
    Fodor's view the world is a logical system, to be computed as a formal
    system (This is also a hardened version of the increasingly discredited
    Chomskyan view).  Here he's also reviewing Evolution in Mind by Henry
    Plotkin. ]

It belongs to the millennial mood to want to sum things up and see where we
have gotten and point in the direction that further progress lies. Cognitive
science has not been spared this impulse...

Like Pinker and Plotkin, I think the New Rationalism is
the best story about the mind that science has found to tell so far. But I
think their version of that story is tendentious, indeed importantly
flawed. And I think the cheerful tone that they tell it in is quite
unwarranted by the amount of progress that has actually been made. Our best
scientific theory about the mind is better than empiricism; but, in all sorts
of ways, it's still not very good.

Pinker quotes Chomsky's remark the 'ignorance can be divided into problems
and mysteries' and continues: 'I wrote this book because dozens of mysteries
of the mind, from mental images to romantic love, have recently been upgraded
to problems (though there are still some mysteries too!)' Well, cheerfulness
sells books, but Ecclesiastes got it right: 'the heart of the wise is in the
house of mourning.'

Pinker elaborates his version of rationalism around four basic ideas: the
mind as computational system; the mind is massively modular; a lot of mental
structure, including a lot of cognitive structure, is innate; a lot of mental
structure, including a lot of cognitive structure, is an evolutionary
adaptation - in particular, the function of a creature's nervous system is to
abet the propagation of its genome (its selfish gene, as one says).  ... take
for granted that psychology should be a part of biology and they are both
emphatic about the need for more Darwinian thinking in cognitive science.
(Plotkin quotes with approval Theodore Dobzhansky's dictum that 'nothing in
biology makes sense except in the light of evolution,' amending it, however,
to read 'makes complete sense'.) It's their Darwinism, specifically their
allegiance to a 'selfish gene' account of the phylogeny of the mind, that
most strikingly distinguishes Pinker and Plotkin from a number of their
rationalist colleagues (and from Chomsky in particular).  I'm particularly
interested in how much of the Pinker-Plotkin consensus turns on the stuff
about selfish genes, of which I don't, in fact, believe a
word.

Computation. Beyond any doubt, the most important thing that has
happened in cognitive science was Turing's invention of the notion of
mechanical rationality. Here's a quick, very informal, introduction.
(Pinker provides one that's more extensive).

It's a remarkable fact that you can tell, just by looking at it, that any
sentence of the syntactic form P and Q ('John swims and Mary drinks', as it
might be) is true only if P and Q are both true. 'You can tell just by
looking' means: to see that the entailments hold, you don't have to know
anything about what either P or Q means and you don't have to know anything
about the non-linguistic world. This really is remarkable since, after all,
it's what they mean, together with how the non-linguistic world is, that
decide whether P of Q is itself true. This line of thought is often
summarised by saying that some inferences are rational in virtue of the
syntax of the sentences that enter into them; metaphorically, in virtue of
the 'shapes' of these sentences.

Turing noted that, wherever an inference is formal in this sense, a machine
can be made to execute the inference. This is because, although machines are
awful at figuring out what's going on in the world, you can make them so that
they are quite good at detecting and responding to syntactic relations among
sentences.

... some, at least, of what makes minds rational is their ability to perform
computations on thoughts; where thoughts, like sentences, are assumed to be
syntactically structured and where 'computations' means formal operations in
the manner of Turing. It's this theory that Pinker has in mind when he claims
that 'thinking is a kind of computation'. It has proved to be a simply
terrific idea. Like Truth, Beauty and Virtue, rationality is a normative
notion; the computational theory of mind is the first time in all of
intellectual history that a science has been made out of one of those. If God
were to stop the show now and ask us what we've discovered about how we
think, Turing's theory of computation is far the best thing that we could
offer.

But Turing's account of computation is, in a couple of senses, local. It
doesn't look past the form of sentences to their meanings; and it assumes
that the role of thoughts in a mental process is determined entirely by their
internal (syntactic) structure. And there's reason to believe that at least
some rational processes are not local in either of these respects. It may be
that wherever either semantic or global features of mental processes begin to
make their presence felt, you reach the limits of what Turing's kind of
computational rationality is able to explain. As things stand, what's beyond
these limits is not a problem but a mystery. I think it's likely, for
example, that a lot of rational belief formation turns on what philosophers
call 'inferences to the best explanation'. You've got what perception
presents to you as currently the fact and you've got what memory presents to
you as the beliefs that you've formed till now, and your cognitive problem is
to find and adopt whatever new beliefs are best confirmed on balance. 'Best
confirmed on balance' means something like: the strongest and simplest
relevant beliefs that are consistent with as many of one's prior epistemic
commitments as possible. But, as far as anyone knows, relevance, strength,
simplicity, centrality and the like are properties, not of single sentences,
but of whole belief systems; and there's no reason at all to suppose that
such global properties of belief systems are syntactic. In my view, the
cognitive science that we've got so far has hardly begun to face this
issue. Most practitioners (Pinker and Plotkin included, as far as I can tell)
hope that it will resolve itself into lots of small, local problems which
will in turn succumb to Turing's kind of treatment. Well, maybe; it's
certainly worth the effort of continuing to try. But I'm impressed by this
consideration: our best cognitive science is the psychology of perception,
and (see just below) it may well be that perceptual processes are largely
modular, hence computationally local. Whereas, plausibly, the globality of
cognition shows up clearest in the psychology of common
sense. Uncoincidentally, as things now stand, we don't have a theory of the
psychology of common sense that would survive serious scrutiny by an
intelligent five-year-old. Likewise, common sense is egregiously what the
computers that we know how to build don't have. I think it's likely that we
are running into the limits of what can be explained with Turing's kind of
computation; and I think we don't have any idea what to do about it.

Suffice it to say, anyhow, that if your notion of computation is exclusively
local, then your notion of mental architecture had best be massively
modular. That brings us to the second tenet of the Pinker-Plotkin version of
Rationalism.

Massive modularity. A module is a more or less autonomous, special purpose,
computational system. It's built to solve a very restricted class of
problems, and the information it can use to solve them with is
proprietary. Most of the New Rationalists think that at least some human
cognitive mechanisms are modular, aspects of perception being among the
classical best candidates. For example, the computations that convert a
two-dimensional array of retinal stimulations into a stable image of a three
dimensional visual world are supposed to be largely autonomous with respect
to the rest of one's cognition. That's why many visual illusions don't go
away even if you know that they are illusory.

Both Pinker and Plotkin think the mind is mostly made of modules; that's the
massive modularity thesis in a nutshell. I want to stress how well it fits
with the idea that mental computation is local. By definition, modular
problem-solving works with less than all the information that a creature
knows. It thereby minimises the global cognitive effects that are the bane of
Turing's kind of computation. If the mind is massively modular, then maybe
the notion of computation that Turing gave us is, after all, the only one
that cognitive science needs. It would be nice to be able to believe that;
Pinker and Plotkin certainly try very hard to do so. But, really, one
can't. For, eventually the mind has to integrate the results of all those
modular computations and I don't see how there could be a module for doing
that. The moon looks bigger when it's on the horizon; but I know perfectly
well it's not. My visual perception module gets fooled, but I don't. The
question is: who is this I? And by what -presumably global - computational
process doe sit use what I know about the astronomical facts to correct the
misleading appearances that my visual perception module insists on computing?
If, in short, there is a community of computers living in my head, there had
also better be somebody who is in charge; and, by God, it had better be
me. The Old Rationalists, like Kant, thought that the integration of
information is a lot of what's required to turn it into knowledge. If that's
right, then a cognitive science that hasn't faced the integration problem has
barely got off the ground.

Probably, modular computation doesn't explain how minds are rational; it's
just a sort of precursor. It's what you have to work through to get a view of
how horribly hard our rationality is to understand. Innateness. Rationalists
are nativists by definition; and nativism is where cognitive science touches
the real world. As both Pinker and Plotkin rightly emphasise, the standard
view in current social science - and in what's called 'literary theory' -
takes a form of Empiricism for granted: human nature is arbitrarily plastic
and minds are social constructs. By contrast, the evidence from cognitive
science is that a lot of what's in the modules seems to be there
innately. Pinker and Plotkin both review a fair sample of this evidence,
including some of the lovely experimental work on infant cognition that
psychologists have done in the last couple of decades. There is also, as the
linguists have been claiming for years, a lot of indirect evidence that
points to much the same conclusion: all human languages appear to be
structurally similar in profound and surprising ways. There may be an
alternative to the nativist explanation that linguistic structure is
genetically specified; but, if there is, nobody has thus far had a glimpse of
it. (For a review, see Pinker's earlier book, The Language
Instinct). Cultural relativism is widely held to be politically correct. So,
sooner or later, political correctness and cognitive science are going to
collide. Many tears will be shed and many hands will be wrung in public. Be
that as it may; if there is a human nature, and it is to some interesting
extent genetically determined, it is folly for humanists to ignore it. We're
animals whatever else we are; and what makes an animal well and happy and
sane depends a lot on what kind of animal it is. Pinker and Plotkin are both
very good on this; I commend them to you. But, for present purposes, I want
to examine a different aspect of their Rationalism.

Psychological Darwinism. Pinker and Plotkin both believe that if nativism is
the right story about cognition, it follows that much f our psychology must
be, in the Darwinian sense, an evolutionary adaptation; that is, it must be
intelligible in light of evolutionary selection pressures that shaped
it. It's the nativism that makes cognitive science politically
interesting. But it's the inference from nativism to Darwinism that is
currently divisive within the New Rationalist community. Pinker and Plotkin
are selling an evolutionary approach to psychology that a lot of cognitive
scientists (myself included) aren't buying. There are two standard arguments,
both of which Pinker and Plotkin endorse, that are supposed to underwrite the
inference from nativism to psychological Darwinism. The first is empirical,
the second methodological. I suspect that both are wrong-headed.

The empirical argument is that, as a matter of fact, there is no way except
evolutionary selection for Nature to build a complex, adaptive
system.  ... Pinker says: 'Natural selection is the
only explanation we have of how complex life can evolve . . . [so] natural
selection is indispensable to understanding the human mind.'
there's another way
out of the complexity argument. This is a long story, but here's the gist:
it's common ground that the evolution of our behaviour was mediated by the
evolution of our brains. So, what matters with regard to the question whether
the mind is an adaptation is not how complex our behaviour is, but how much
change you would have to make in an ape's brain to produce the cognitive
structure of a human mind. And about this, exactly nothing is known. That's
because nothing is known about how the structure of our minds depends on the
structure of our brains. Nobody even knows which brain structures it is that
our cognitive capacities depend on.




... Make the giraffe's neck just a little longer and you correspondingly
increase, by just a little, the animal's capacity to reach he fruit at the
top of the tree. So it's plausible, to that extent, that selection stretched
giraffes' necks bit by bit. But make an ape's brain just a little bigger (or
denser, or more folded, or, who knows, greyer) and it's anybody's guess what
happens to the creature's behavioural repertoire. Maybe the ape turns into
us....

One last point about the status of the inference from nativism to
psychological Darwinism. If the mind is mostly a collection of innate
modules, then pretty clearly it must have evolved gradually, under selection
pressure. That's because, as I remarked above, modules contain lots of
specialised information about the problem-domains that they compute in. And
it really would be a miracle if all those details got into brains via a
relative small, fortuitous alteration of the neurology. To put it the other
way around, if adaptationism isn't true in psychology, it must be that what
makes our minds so clever is something pretty general; something about their
global structure. The moral is that if you aren't into psychological
Darwinism, you shouldn't be into massive modularity either. Everything
connects. For the sake of the argument, however, let's suppose that the mind
is an adaptation after all and see where that leads. It's a point of
definition that adaptations have to be for something. Pinker and Plotkin both
accept the 'selfish gene' story about what biological adaptations are
for. Organic structure is (mostly) in aid of the propagation of the
genes. And so is brain structure inter alia. And so is cognitive structure,
since how the mind works depends on how the brain does. So there's a route
from Darwinism to socio-biology; and Pinker, at least, is keen to take it.

A lot of the fun of Pinker's book is his attempt to deduce human psychology
from the assumption that our minds are adaptations for transmitting our
genes. His last chapters are devoted to this and they range very broadly;
including, so help me, one on the meaning of life. Pinker would like to
convince us that the predictions that the selfish-gene theory makes about how
our minds must be organised are independently plausible. But this project
doesn't fare well.

Prima facie, the picture of the mind, indeed of human nature in general, that
psychological Darwinism suggest is preposterous; a sort of jumped up,
down-market version of original sin. Psychological Darwinism is a kind of
conspiracy theory; that is, it explains behaviour by imputing an interest
(viz in the proliferation of the genome) that the agent of the behaviour does
not acknowledge. When literal conspiracies are alleged, duplicity is
generally part of the charge: 'He wasn't making confetti; he was shredding
the evidence. He did X in aid of Y, and then he lied about his motive.' But in
the kind of conspiracy theories psychologists like best, the motive is
supposed to be inaccessible even to the agent, who is thus perfectly sincere
in denying the imputation. In the extreme case, it’s hardly even the agent to
whom the motive is attributed. Freudian explanations provide a familiar
example: What seemed t be merely Jones’s slip of the tongue was the
unconscious expression of a libidinous impulse. But not Jones’s libidinous
impulse, really; one that his Id had on his behalf. Likewise, for the
psychological Darwinist: what seemed to be your, after all, unsurprising
interest in your child’s well-being turns out to be your genes’ conspiracy to
propagate themselves. Not your conspiracy, notice, but theirs.

How do you make the case that Jones did X in aid of an interest in Y, when Y
is an interest that Jones doesn't own to? The idea is perfectly familiar: you
argue that X would have been the rational (reasonable, intelligible) thing
for Jones to do if Y had been his motive. Such arguments can be very
persuasive. The files Jones shredded were precisely the ones that would have
incriminated him; and he shredded them in the middle of the night. What
better explanation than that Jones conspired to destroy the evidence?
Likewise when the conspiracy is unconscious. Suppose that an interest in the
propagation of the genome would rationalise monogamous families I animals
whose offspring mature slowly. Well, our offspring do mature slowly; and our
species does, by and large, favour monogamous families. So that's evidence
that we favour monogamous families because we have an interest in the
propagation of our genes.
Well, isn't it? Maybe yes, maybe no; this kind of
inference needs to be handled with great care. For, often enough, where an
interest in X would rationalise Y, so too would an interest in P, Q or
R. It's reasonable of Jones to carry an umbrella if it's raining and he wants
to keep dry. But, likewise, it's reasonable for Jones to carry an umbrella if
he has in mind to return it to its owner. Since either motivation would
rationalise the way that Jones behaved, his having behaved that way is
compatible with either imputation. This is, in fact, overwhelmingly the
general case: there are, most often, all sorts of interests which would
rationalise the kinds of behaviour that a creature is observed to
produce. What's needed to make it decisive that the creature is interested in
Y is that it should produce a kind of behaviour that would be reasonable only
given an interest in Y. But such cases are vanishingly rare since, if an
interest in Y would rationalise doing X, so too would an interest in doing
X. A concern to propagate one's genes would rationalise one's acting to
promote one's children's welfare; but so too would an interest in one's
childrens' welfare. Not all of one's motives could be instrumental, after
all; there must be some things that one cares for just for their own
sakes. Why, indeed, mightn't there be quite a few such things? Why shouldn't
one's children be among them?

The literature of Psychological Darwinism is full of what appear to be
fallacies of rationalisation: arguments where the evidence offered that an
interest in Y is the motive for a creature's behaviour is primarily that an
interest in Y would rationalise the behaviour if it were the creature's
motive. Pinker's book provides so many examples that one hardly knows where
to start. Here he is on friendship:

    Once you have made yourself valuable to someone, the person becomes
    valuable to you. You value him or her because if you were ever in
    trouble, they would have a stake - albeit a selfish stake - in getting
    you out. But now that you value the person, they should value you even
    more . . . because of your stake in rescuing him or her from hard times
    . . . This runaway process is what we call friendship.'

And here he is on why we like to read fiction: 'Fictional narratives supply
us with a mental catalogue of the fatal conundrums we might face someday and
the outcomes of strategies we could deploy in them. What are the options if I
were to suspect that my uncle killed my father, took his position, and
married my mother?' Good question. Or what if it turns out that, having just
used the ring that I got by kidnapping a dwarf to pay off the giants who
built me my new castle, I should discover that it is the very ring that I
need in order to continue to be immortal and rule the world? It's important
to think out the options betimes, because a thing like that could happen to
anyone and you can never have too much insurance. At one point Pinker quotes
H.L. Mencken's wisecrack that 'the most common of all follies is to believe
passionately in the palpably not true.' Quite so. I suppose it could turn out
that one's interest in having friends, or in reading fictions, or in Wagner's
operas, is really at heart prudential. But the claim affronts a robust, and I
should think salubrious, intuition that there are lots and lots of things
that we care about simply for themselves. Reductionism about this plurality
of goals, when not Philistine or cheaply cynical, often sounds simply
funny. Thus the joke about the lawyer who is offered sex by a beautiful
girl. 'Well, I guess so,' he replies, 'but what's in it for me?' Does wanting
to have a beautiful woman - or, for that matter, a good read - really require
a further motive to explain it? Pinker duly supplies the explanation that you
wouldn't have thought that you needed. 'Both sexes want a spouse who has
developed normally and is free of infection . . . We haven't evolved
stethoscopes or tongue-depressors, but an eye for beauty does some of the
same things . . . Luxuriant hair is always pleasing, possibly because
. . . long hair implies a long history of good health.'

Much to his credit, Pinker does seem a bit embarrassed about some of these
consequences of his adaptationism, and he does try to duck them.

    Many people think that the theory of the selfish gene says that 'animals
    try to spread their genes'. This misstates . . . the theory. Animals,
    including most people, know nothing about genetics and care even
    less. People love their children not because they want to spread their
    genes (consciously or unconsciously) but because they can't help
    it. . . What is selfish is not the real motives of the person but the
    metaphorical motives of the genes that built the person. Genes 'try' to
    spread themselves (sic) by wiring animals brains so that animals love
    their kin . . . and then the[y] get out of the way.

This version sounds a lot more plausible; strictly speaking, nobody has as a
motive ('conscious or unconscious') the proliferation of genes after all. Not
animals, and not genes either. The only real motives are the ones that
everybody knows about; of which love of novels, or women, or kin are
presumably a few among many. But, pace Pinker, this reasonable view is not
available to a psychological Darwinist. For to say that the genes 'wire
animals brains so that animals love their kin' and to stop there is to say
only that loving their kin is innate in these animals. That reduces
psychological Darwinism to mere nativism; which, as I remarked above, is
common ground to all of us Rationalists. The difference between Darwinism and
mere nativism is the claim that a creature's innate psychological traits are
adaptations; viz that their role in the propagation of the genes is what
they're for. Take the adaptationism away from a psychological Darwinist and
he has nobody left to argue with except empiricists. It is, then,
adaptationism that makes Pinker and Plotkin's kind of rationalism
special. Does this argument among nativists really matter? Nativism itself
clearly does; everybody cares about human nature. But I have fussed a lot
about the difference between nativism and Darwinism, and you might reasonably
want to know why anyone should care about that.

For one thing, nativism says there has to be a human nature, but it's the
adaptationism that implies the account of human nature that sociobiologists
endorse. If, like me, you find that account grotesquely implausible, it's
perhaps the adaptationism rather than the nativism that you ought to consider
throwing overboard. Pinker remarks that 'people who study the mind would
rather not have to think about how it evolved because it would make a hash of
cherished theories . . . When advised that [their] claims are evolutionarily
implausible, they attack the theory of evolution rather than rethinking the
claim.' I think this is exactly right, though the formulation is a bit
tendentious. We know - anyhow we think that we do - a lot about ourselves
that doesn't seem to square with the theory that our minds are adaptations
for spreading our genes. The question may well come down to which theory we
should give up. Well, as far as I can tell, if you take away the bad argument
that turns on complexity, and the bad argument from reverse engineering, and
the bad arguments that depend on committing the rationalisation fallacy, and
the atrociously bad arguments that depend on preempting what's to count as
the 'scientific' (and/or the biological) world view, the direct evidence for
psychological Darwinism is very slim indeed. In particular, it's arguably
much worse than the indirect evidence for our intuitive, pluralistic theory
of human nature. It is, after all, our intuitive pluralism that we use to get
along with one another. And I have the impression that, by and large, it
works pretty well.