V&m Res. Vol. 12, pp. 623-624. Peqpmon Press t972 Printed in Great Brimia. THE EFFECTS OF VISUAL DEPRIVATION ON THE DEPTH PERCEPTION OF ADULT AND INFANT RATS AND ADULT SQUIRREL MONKEYS (SAIMIRI SCIUREA) VINCENT SUIMIN, JR. and ROBWT PASNM? Dcpwtmcnt of Psychology, The Catholic University of Am&i, Wash&on D.C. 20017, U.S.A. (Rcc&ed 15 &ust 1971; in revisedform 7 October 1971) MANY primitive organisms show immediate and highly uniform reactions to light from the moment of birth. How much of this capacity is innate and bow much is acquired by learn- ing or through the natural maturation of the visual nervous system during the animal’s early development? What are the factors that determine visual depth perception? WALK, GIBSON and TIGHE (1957) found that dark-reamd hooded rats showed no deficit in visual cliff performance, supporting the conclusion of LASILEY and RUSSELL (1934) that depth perception in the rat is innate. The results of Walk et al. were confirmed for both hooded and albino rats (NEALEY and EDWAIUX, 1960; WALK and GIBSON, 1961; CARR and M&UI(UN, 1965). However, WALK and RCBND (1968) showed that when the depth dis- crimination was made difficult, 9Oday-old dark-reared hooded rats showed a deficit which was still present after 2 weeks in the light. The research reported here is partially an attempt to confirm this finding. Data for adult rats are also reported since GYLL.ENST& MALMFOIU and NORRLIN (1965)found approximately equal decmases in volume of intercellular material in the cortex and subcortical centers of both infant and aduh mice deprived of light for 3 months. It is thus theoretically important to determine whether the behavioural conse- quences of light deprivation, heretofore considered essentially a developmental phenome- non, also apply to visually experienced animals. Although RIESEN (1950) has shown that deprivation of light causes severe physiological and behavioural defects in a young chimp- anxee which bad had extensive visual experience, no eff’ has been found for the adult cat (w, 1965; HUBEL and WIESEL, 1970; JONES and PASMK, 1970). Hence comparative measurements are presented from adult squirrel monkeys as well as from adult rats to provide some idea of the phylogenetic generality of the effect of light deprivation on adults. The apparatus of choice is the visual cliff, since it providesastand means for testing the depth perception of animals and has the critical advantage of requiring no training period. Method EXPERIMENT 1 Subjects. The Ss were four adult (8-10 months) female 8quirrclrnoukcy8 (&MA sciu&. Appmwrus. The apparatus was the visual cliff model II illustrated in WALX and GIBSON (1961). T&a box ~~~&Itb~andmnstntctsdofiin,p~withoutside~~#) x 3Zbt,andsidcs14in. wide c&erboard. A cloth with 4 in. blue stripes was the discriminator ’ This rcldlcch was supported by PHS Grant FRO7123-01.Special thanks are oxtetuied to RI- WALK for gracious advic8 and criticism, and to RIK?IN~ PIJRYEAR for hiacoutributiom to these axp&nents. 623