Department of Neurology, University Hospital Zurich.
To study the influence of motivational expectancy on perception, the ambiguous drawing of a duck/rabbit was shown to 265 subjects on Easter and to 276 subjects in October. The ambiguous drawing, though perceived as a bird by a majority of subjects in October, was most frequently named a bunny on Easter. This biasing effect of expectancy upon perception was observed for young children (2 to 10 years) as well as for older subjects (11 to 93 years).