Friday, March 09, 2007

The courage of a mouse to say 'No': A case of metacognition or risk-aversion?

A recent article in Current Biology by Foote et al (courtsey Ars Technica) posits that rats have metacognition abilities. till now only Humans and primates were assumed to have metacognitive abilities. One feature or defining characteristic of metacognition is knowing what you know and also knowing what you don't know. It means one can think about one's own mental states and determine what knowledge one already has and what knowledge one has not yet learned. So a related ability would be the ability to decline a test of knowledge if one thinks that one has not learned enough to ace the test. For those who gave GRE/ any other exam recently and maybe postponed that exam, they would have no difficulty appreciating this that postponing/declining a test involves metacognition.

Taking this line of reasoning further, Foote et al surmise that if a rat could decline a test, under conditions when the rat was not sure of its learned knowledge regarding the test and doubted its ability to successfully complete the test, then such a declining behavior would indicate that the rat has metacognitive abilities. I find no flaws in this reasoning, but have a few quips about their particular experimental setup, which may have confounded the results by not factoring in the risk aversion.

First regarding their hypothesis of the experiment:

Here, we demonstrate for the first time that rats are capable of metacognition—i.e., they know when they do not know the answer in a duration-discrimination test. Before taking the duration test, rats were given the opportunity to decline the test. On other trials, they were not given the option to decline the test. Accurate performance on the duration test yielded a large reward, whereas inaccurate performance resulted in no reward. Declining a test yielded a small but guaranteed reward. If rats possess knowledge regarding whether they know the answer to the test, they would be expected to decline most frequently on difficult tests and show lowest accuracy on difficult tests that cannot be declined [4]. Our data provide evidence for both predictions and suggest that a nonprimate has knowledge of its own cognitive state.

Now on to the actual experimental setup:


Each trial consisted of three phases: study, choice, and test phases (Figure 1). In the study phase, a brief noise was presented for the subject to classify as short (2–3.62 s) or long (4.42–8 s). Stimuli with intermediate durations (e.g., 3.62 and 4.42 s) are most difficult to classify as short or long [11, 12]. By contrast, more widely spaced intervals (e.g., 2 and 8 s) are easiest to classify. In the choice phase, the rat was sometimes presented with two response options, signaled by the illumination of two nose-poke apertures. On these choice-test trials, a response in one of these apertures (referred to as a take-the-test response) led to the insertion of two response levers in the subsequent test phase; one lever was designated as the correct response after a short noise, and the other lever was designated as the correct response after a long noise. The other aperture (referred to as the decline-the-test response) led to the omission of the duration test. On other trials in the choice phase, the rat was presented with only one response option; on these forced-test trials, the rat was required to select the aperture that led to the duration test (i.e., the option to decline the test was not available), and this was followed by the duration test. In the test phase, a correct lever press with respect to the duration discrimination produced a large reward of six pellets; an incorrect lever press produced no reward. A decline response (provided that this option was, indeed, available) led to a guaranteed but smaller reward of three pellets.

The test they have used is a stimulus discrimination test. Their results indicated that indeed the rats declined more often on difficult trials (trials in which the stimulus were closely spaced around the men of 4s) as compared to easy trial (in which they had to discriminate widely spaced stimulus (say 2s and 8s). This neatly demonstrates that the rats were internally calculating what their odds of passing the test were, and in case of the difficult test they took the better option of choosing the decline-the-test condition. However I would like to see more of their data and factor out the effcets of risk aversion.

We all know that humans are prone to risk aversion. That is if I present to you an option of choosing a sure amount of 100 rs or a 50% chance of winning 200rs , you would normally choose the fist option, though if one compares the utility function it is the same. In first case you have and expected value of 100 and in the second case too you have an expected value of 100 (0.5*0 +0.5*200). Thus it doesnt make much sense why one would use one over the other. This becomes more interseting when we increase the amount of the risky option. suppose we now have 100 rs assured vis-avis a 50 % chance of 300 rs still , most of us end up choosing the assured sum.

In this setup the utility of declining the test is 3 pellets; while if we assume that the rats have not learned how to discriminate the stimuli; then assuming that they press the levers at random and thus each option of the test condition is equally probable we have the utility as 0.5 *0 +0.5 *6 = 3 pellets. so we have the same situations as with humans. Now taking risk aversion into account, one would find that the rats would decline the test more often in the difficult stimulus conditions as that is a safe and assured option as compared to the take-the-test condition. As a matter of fact I am surprised that there were some rats who did choose the take-the-test condition. I guess men are more meek than mice!!

So the best thing to do would be to take risk-aversion into account and then after factoring it out decide on whether the rats knew (in a conscious sense) that the test is difficult. Risk aversion is mostly sub-conscious and would not involve metacognition. However, the trend of rising declining behaviors with test difficulty does point to the fact that the rats did have some metacognition.

I would love to have this study replicated using a maze (mouse trap sort of) task. In a amze the cognitive map of the maze provides a good indicataor of how much the mice know about the test/ test difficulty and measuring the declining in this case may be directly related to their meta-cognitive abilities.


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5 comments:

The Kid said...

Hi,

I am a long time reader of your blog, though I cannot claim to be regular. I am very interested in behavioural psychology in general. I should add that my career is not related to psychology in any way.

You blog is my only daily dose of psychology. I think you are doing a great job and the only regret I have is that you write too often :) . It takes twice as long to read your posts because it is technical and follows scientific reasoning.

I hope you do not mind if I ask you questions with respect to your blog posts.

-Pratap

Sandy G said...

Hi Pratap,

Thanks for being a long-time reader. I am glad that you like the contents, though I am afraid that I an not as prolific in my blog posts as some other bloggers are (you should just see the output of some others like the neurophiliosopher, coturnix (a blog around the clock) or SharpBrains). Actually I too end up reading less of these blogs , though I appreciate their content very well, just because of their sheer prolificness :-).Talk about information overload!! If I read every post from every blog that I admire, most probably I'll go bonkers:-)

Though on the other part regarding blog posts being more technical and difficult to read, I'll try my best to avoid jargons as far as possible.And please feel comfortable about asking questions. Blogging is supposed to be interactive and I, personally, would like my blog to be very interactive and would love to involve more and more readers and commentators in the joint exploration of the psychosphere.

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Anonymous said...

Hi Sandy,
Can you provide some more background to your info about risk aversion? You mention that risk aversion is a primarily sub-conscious. Are there studies that back this up? Since your example regarding risk aversion is with human subjects, it's hard to see why risk aversion of this sort might not be tied to metacognition.

Sandy G said...

There is some evidence from priming studies, that priming , which works on a subconscious basis , can affect whether one makes a risk-prone or risk-averse judgment/decision. Please see the following URL

Also, there is growing body of evidence that most decision making is not rational, but either emotional or subconscious. Blink by Malcolm Gladwell is a book regarding this subconsciouses decision making and a good study elaborating on emotion-driven (and hence not cognitive) decision making under risk is the following PDF

I know that even with risk aversion being attributed to emotions like dread of loss, it may still be construed as a conscious feeling and thus maybe compatible with meta cognition.