The three well-practiced adults adopted a strategy of always poking
from the same end of the tube although sometimes they switched ends
across days. In this way they earned food 50% of the time, with
stereotyped, repetitive habits (chap. 11). The three adults stuck to this
strategy for the entire course of 140 trials. Visalberghi and Limongelli
concluded that the overtrained adults, that they described as "expert
tool users," failed to understand the problem in spite of their training.

A relatively inexperienced juvenile female, Rb, did solve the prob-
lem about halfway through the course, but the experimenters kept
her repeating this for another 40 or 50 trials. Doubting that Rb
understood tools better than the well-trained adults, Visalberghi and
Limongelli tested Rb further. In the first test, for example, they rotated
the tube so that the trap was above rather than below the path of
the food. Starting from either end of the tube in this arrangement,
Rb could poke the food safely past the trap, but she stuck to the
strategy she had practiced so well before. She always started the stick
from the end of the tube that was farthest from the lure, and poked
the food out through the near end. She persisted in this habitual
strategy even with straight tubes that lacked any traps at all.

Visalberghi and Limongelli concluded that the now well-practiced
Rb also failed to understand the problem. All she had learned, ac-
cording to them, was to poke the food out by starting the stick from
the far end. On their part, the experimenters failed to consider the
uniformly negative effect of mind-numbing drill on both human and
nonhuman animals throughout the history of research on problem
solving.

Extending the findings of earlier chapters to problem-solving strategy
reveals a basic conflict between skill at repetitive sequences and flexible
attack on new problems. Chapter 11 showed how partial reward
increases resistance to extinction because it separates sequential skill
from reward. Repetitive practice with minimum reward perfects skill
at repetitive tasks, but tolerance for failure delays, even prevents,
problem solving.

Early cognitive approaches like Krechevsky's transposed the effect
of contingency to the reinforcement and extinction of abstract hy-
potheses without taking into account the practical benefit that a
learner gets from general experience with experimental procedures.
Later cognitive approaches like MacKintosh's transposed Skinner's
notions of stamping in responses to the idea that overtraining stamps

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