Domestic chicks were placed in isolation under a constant white light for 30 minutes. Afterwards these birds and a group previously kept in the dark were trained with a Red or a Yellow flashing light for 45 minutes. Subsequently all chicks were given a choice between familiar and unfamiliar flashing lights in some new apparatus which is described in detail for the first time. The chicks exposed to constant light showed a clear preference for the flashing light with which they had been trained whereas the Dark control chicks did not. It is suggested that the constant light activated their visual pathways enabling the Light-exposed chicks to learn more than the Dark control chicks during the imprinting procedure.