Learning to Learn

Harry Harlow proposed a new method for measuring higher learning abilities of animals in 1949. Harlow suggested that humans and other highly intelligent animals not only mastered isolated tasks but also noticed patterns and shortcuts that made them more efficient learners. They not only learned, they learned to learn, becoming faster at solving new problems as they gained experience solving similar classes of problems (Harlow, 1949).

What is "learning to learn"?

Learning to learn, which Harlow also called learning set, means picking out a pattern in a series of learning experiences, so that you learn even faster when facing similar situations in the future. An example in humans would be learning how to study correctly for a class. You might find that you do better as you go along, because you have "learned how to learn" in that class.

How did Harlow study learning set in rhesus monkeys?

Here is an example of a learning set experiment for non-humans. Rhesus monkeys had to decide which of two doors to open. If they selected the correct door, they found food. If they selected the other door, they found no food. Food was put behind the same door for six trials in a row. Each group of six trials was called a block.

If the animal caught on to the pattern (that food was behind the same door for the whole block of six trials) then it should stop making errors on the second trial. Why? Because if the animal guessed wrong on the first try (the first of six in a block), it could switch to the other door and look behind it for the next five trials in the block. If it guessed right on the first try, it should keep choosing that door.

Why would a "smart animal" eventually make no errors on trial 2 in each block of 6?

In accordance with the logic of the experiment, Harlow was interested in each animal's success rate on trial 2 in the block of six. At first, animals performed poorly on trial 2. They guessed randomly or persisted in whatever worked during the previous session. As the experiment went along, the more intelligent animals grasped the pattern of the experiment and started improving their odds of success on trial 2.


Differences in how rapidly species "learn to learn"

A "smart" species like a rhesus monkey improved its success rate on trial #2 until it topped off at 100% (never failing to receive food on trial 2). To less brilliant species, the pattern of the experiment was not so clear. Some animals persisted with whatever worked most recently. If they found food behind door #1 during the last block, they might persist in looking behind the door #1 for all six trials of the second block, even though they were not getting much food as a result. Other animals adopted a random switching strategy, seemingly unable to "pick up" the pattern in the experiment.

Harlow found that rhesus monkeys were fast at improving their percentage on trial #2. Squirrel monkeys were slower (Harlow, 1959). Rats, cats, and raccoons were slower still. Cats were only as smart as pigeons, by this criterion.


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