A higher note is struck in the behaviour of some more highly endowed
monkeys. In many experiments, chiefly in the way of getting into boxes
difficult to open, there is evidence (1) of attentive persistent
experiment (2) of the rapid elimination of ineffective movements, and
(3) of remembering the solution when it was discovered. Kinnaman taught
two macaques the Hampton Court Maze, a feat which probably means a
memory of movements, and we get an interesting glimpse in his
observation that they began to smack their lips audibly when they
reached the latter part of their course, and began to feel, dare one
say, "We are right this time."
In getting into "puzzle-boxes" and into "combination-boxes" (where the
barriers must be overcome in a definite order), monkeys learn by the
trial and error method much more quickly than cats and dogs do, and a
very suggestive fact emphasized by Professor Thorndike is "a process of
sudden acquisition by a rapid, often apparently instantaneous
abandonment of the unsuccessful movements and selection of the
appropriate one, which rivals in suddenness the selections made by human
beings in similar performances." A higher note still was sounded by one
of Thorndike's monkeys which opened a puzzle-box at once, eight months
after his previous experience with it. For here was some sort of
registration of a solution.