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PhilGoetz comments on Over-encapsulation - Less Wrong
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I think I might be spazzing out a bit (I haven't been sleeping well), so let me try to get this straight:
The hypothesis is that a rat will spend more time investigating a new object than an old object - the old object will be ignored as familiar, the new object will be attended to as unfamiliar.
Therefore, if the rats recognize the old object, they will ignore it (time spent examining it will be less); if they do not recognize the old object, they will attend to it (time spent examining it will be more).
...and here is where I get lost. You say that the above assumes that time spent examining new objects should be consistent - are you saying that variations in the new-object times imply confounding factors which corrupt the results?
Technically, yes. But phrasing it that way sounds like the test algorithm should include, "Check that the new object times are consistent". That's not how I detected the error. I said, "Remember that what we originally wanted to know is whether the old object times are different - and they aren't."
The data show the rats spending the same amount of time examining the old objects in all cases. The investigators concluded that the rats didn't recognize the old objects in those cases where they spent less time than usual examining new objects. That interpretation requires believing that it's more likely that the new-object-times plot a strange but reliable function f(M) describing how curious rats are about new objects M minutes after being exposed to a different object, than that your experiment is messed up.
Note also the leftmost two points in figure 1B. This shows that the control rats and the gene-therapy rats both spent the same amount of time investigating the old objects. So now, to continue with the interpretation that the new-object-time is a good control, you have to believe that the gene therapy has both improved the rats' ORM, and made them more inherently curious about objects shown to them 60 minutes after being shown some other object.
In other words, if the setup were good, the old object time ought to increase, rather than the new object time decrease.
That's what I'd expect to see.