Sir: The answer to Alec Just's memory problem (Letters, 29 May) was first explained by the German psychologist Elizabeth Zeigarnik in 1927 when she found that memory for uncompleted tasks was superior to that for completed tasks. Interrupted, or uncompleted, tasks generate "tension". However, this tension dissipates over a relatively short period of time, certainly less than 24 hours, after which there is no difference in task recall. Hence Mr Just's daily dilemma.
My solution to Mr Just's specific problem is that he cleans all but one of his teeth. Adopting a rota for omission should help to ensure continued dental hygiene. Alternatively, he could try drinking all his coffee.
Dr PETER DAVIES
Head of Department of Psychology
University of Leeds