Screening cervical smears.

A plausible explanation is offered why an experienced pathologist engaged in the screening of cervical smears should have issued a large number of false-negative diagnoses. The explanation centres on the interactions which occur between successive judgements when a sequence of similar stimuli are inspected. Briefly, those interactions have the character of an assimilation of each judgement to its predecessor, and the resultant process is capable of 'running away'. A procedure is suggested, involving the provision of immediate knowledge of results for a small proportion of the smears inspected, which would prevent such systematic misdiagnoses from recurring in the future.