Tag Archives: Wang

Quantum Cognition

Posted on by
8

cats jailedWe know all about the theory espoused by Roger Penrose and Stuart Hameroff, that consciousness is generated by a novel (and somewhat mysterious) form of quantum mechanics which occurs in the microtubules of neurons. For Penrose this helps explain how consciousness is non-computational, a result he has provided a separate proof for.

I have always taken it that this theory is intended to explain consciousness as we know it; but there are those who also think that quantum theory can provide a model which helps explain certain non-rational features of human cognition. This feature in the Atlantic nicely summarises what some of them say.

One example of human irrationality that might be quantumish is apparently provided by the good old Prisoner’s Dilemma. Two prisoners who co-operated on a crime are offered a deal. If one rats, that one goes free while the other serves three years. If both rat, they serve two years; if neither do, they do one year. From a selfish point of view it’s always better to rat, even though overall the no-rat strategy leads to least time in jail for the prisoners. Rationally, everyone should always rat, but in fact people quite often behave against their selfish interest by failing to do so. Why would that be?

Quantum theorists suggest that it makes more sense if we think of the prisoners being in a superposition of states between ratting and not-ratting, just as Schroedinger’s cat superimposes life and death. Instead of contemplating the possible outcomes separately, we see them productively entangled (no, I’m not sure I quite get it, either).

There is of course another explanation; if the prisoners see the choice, not as a one-off, but as one in a series of similar trade-offs, the balance of advantage may shift, because those who are known to rat will be punished while those who don’t may be rewarded by co-operation . Indeed, since people who seek to establish implicit agreements to co-operate over such problems will tend to do better overall in the long run, we might expect such behaviour to have positive survival value and be favoured by evolution.

A second example of quantum explanation is provided by the fact that question order can affect responses. There’s an obvious explanation for this if one question affects the context by bringing something to the forefront of someone’s mind. Asking someone whether they plan to drive home before asking them whether they want another drink may produce different results from asking the other way round for reasons that are not really at all mysterious. However, it’s not always so clear cut and research demonstrates that a quantum model based on complementarity is really pretty good at making predictions.

How seriously are we to take this? Do we actually suppose that exotic quantum events in microtubules are directly responsible for the ‘irrational’ decisions? I don’t know exactly how that would work and it seems rather unlikely. Do we go to the other extreme and assume that the quantum explanations are really just importing a useful model – that they are in fact ultimately metaphorical? That would be OK, except that metaphors typically explain the strange by invoking something understood. It’s a little weird to suppose we could helpfully explain the incomprehensible world of human motivation by appealing to the readily understood realm of quantum physics.

Perhaps it’s best to simply see this as another way of thinking about cognition, something that surely can’t be bad?

Mind-meld rats

Posted on by
11

ratsThis paper  by Pais-Vieira, Lebedev, Kunicki, Wang, and Nicolelis has attracted a great deal of media attention. The BBC described it as ‘literally mind-boggling’. It describes a series of experiments in which the minds of two rats were apparently melded to act as one.

Or does it? One rat, the ‘encoder’ was given a choice of levers to push – left or right (in some cases a more rat-friendly nose-activated switch was used instead of a lever). If it selected the correct one when cued, it got a reward in form of a few drops of water (it seems even lab rats are not getting the rewards they used to these days). Some of the rats learned to pick the right lever in 95% of cases and these went on to the next stage where the patterns of activation from their sensorimotor cortex as they pushed the right lever were picked up and transmitted.

Meanwhile ‘decoder’ rats had been fitted with similar brain implants and trained to respond to a series of impulses delvered in the same sensorimotor area by pressing the right lever. In this training stage they were not receiving impulses from another rat, just an artificially produced stream of blips. This phase of training apparently took about 45 days.

Finally, the two rats were joined up and lo: the impulses recorded from the ‘encoder’ rat, once delivered to the brain of the ‘decoder’ rat, enabled it to hit the right lever with up to 70% accuracy (you could get 50% from random pressing, of course, but it’s still a significant improvement in performance). In one pointless variation, the encoder and decoder rats were in different labs thousands of miles apart; so what? Are we still amazed that electrical signals can be transmitted over long distances?

A couple of other aspects of the experiments seem odd to me. They did not have a control experiment where the signals went to a different part of the decoder rat’s cortex, so we can’t tell whether the use of the particular areas they settled on was significant. Second, they provided the encoder rat with incentives: it got water only when the decoder rat got it right. What was that meant to achieve, apart from making the encoder rat’s life slightly worse than it already was? In essence, it encourages the encoder rat to develop effective signals: to step up the clarity and strength of the neural signals it was sending out. That may have helped to make the experiment a success, but it also detracts from any claim that what was being sent was normal neural activity.

So, what have we got, overall? Really, nothing to speak of. We’re encouraged to think that the decoder rat was hearing the encoder’s thoughts, or feeling its inclinations, or something of the kind, but there’s clearly a much simpler explanation baked into the experiment: it was simply responding to electric impulses of a kind that it had already been trained to respond to (for 45 days, which must be the rat equivalent of post-doctorate levels of lever-pushing knowledge).

Given the lengthy training and selection of the rats, I don’t think a 70% success rate is that amazing: it seems clear that they could have got a better rate if, instead of inserting precise neural connections, they had simply clipped an electrode to the decoder rat’s left ear.

There’s no evidence here of direct transmission of cognitive content: the simple information transferred is delivered via the association already trained into the ‘decoder’. There’s no decoding, and no communication in rat mentalese.

The discussion in the paper ends with the following remarkable proposition.

 …in theory, channel accuracy can be increased if instead of a dyad a whole grid of multiple reciprocally interconnected brains are employed. Such a computing structure could define the first example of an organic computer capable of solving heuristic problems that would be deemed non-computable by a general Turing-machine. Future works will elucidate in detail the characteristics of this multi-brain system, its computational capabilities, and how it compares to other non-Turing computational architectures…

Well, I’m boggling now.