Interpretation of plantar reflexes: biasing effect of other signs and symptoms.

Twenty neurologists were asked to judge a number of plantar responses on film. Each film was preceded by a slide with a fictitious abstract of history and examination (minus the plantar reflex). The main part of the presentation only served to disguise the fact that two films, both showing equivocal toe movements, were presented twice at the same sitting, but with opposing information as to the probability of a Babinski sign. Interpretation of these identical pictures differed significantly (P less than 0.01), conforming to the information given. Thirty other neurologists who rated the films without previous data showed no such change of opinion.