handled the ‘bright’ rats–the ones of which they had higher expectations–more warmly and gently. This treatment changed the rats’ behaviour and enhanced their performance. In the wake of his experiment, a radical idea took root in Rosenthal’s mind; a conviction that he had discovered an invisible yet fundamental force. ‘If rats became brighter when expected to,’ Rosenthal speculated in the magazine American Scientist, ‘then it should not be farfetched to think that children could become brighter when expected to by their teachers.’
