He used sweets, tokens, noises and points to reward children who correctly responded to pictures of a rocket at a certain angle projected on to a screen. He even used Green Shield stamps.
He wanted to see if children showed the same frustration as rats when rewards were withheld.
Some children were more affected than others. Children who were shown on psychological tests to be neurotic extroverts or impulsive were highly sensitive to being rewarded but showed a low sensitivity to frustration and punishment. The reverse was true for neurotic introverts or anxious children whose emotional response to frustration was more energetic responses.
These findings were relevant to educational practice. "The existence of individual differences surely argues in favour of differential treatment of children whose nervous systems predispose them to respond to one kind of motivation rather than another.
"We are not merely dealing with quirks arising from differential early experiences, a fact which ought perhaps to be borne in mind by teachers anxious to make a child more outgoing or less impulsive."