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The results are apparently discussed here:

http://cranepsych.edublogs.org/files/2009/06/Dull_rats_brigh...

The time difference is many seconds (almost minutes).

I can't speak for that study in particular, but it doesn't really matter if it was the touch so long as it was not a measurement effect. There has been a decent amount of research on the Pygmalion effect in varying contexts; it's opposite, the Golem effect, has had its share of research too. It's not an obscure phenomenon at this point.

http://en.wikipedia.org/wiki/Pygmalion_effect

http://en.wikipedia.org/wiki/Golem_effect

Yes I too was interested to know how they eliminated bias. If you were told one rat was smarter than the other, surely there's a risk of influencing the interpretation of results.