362 ReportsInvest. Ophthalmol. Vis. Sci.August 19816. Wiesel TN and Hubel DH: Single cell responses inthe striate cortex of kittens deprived of vision in oneeye. J Neurophysiol 26:1003, 1963.7. Blakemore C and Van Sluyters RC: Reversal of thephysiological effects of monocular deprivation in kit-tens: further evidence for a sensitive period. JPhysiol 237:195, 1974.8. Movshon JA: Reversal of the physiological effects ofmonocular deprivation in the kitten's visual cortex. JPhysiol 261:125, 1976.9. Giffin F and Mitchell DE: The rate of recovery ofvision after early monocular deprivation in kittens. JPhysiol 274:511, 1978.10. Crewther DP, Crewther SG, and Pettigrew JD: Arole for extraocular afferents in post-critical periodreversal of monocular deprivation. J Physiol 282:181, 1978.11. Freeman RD and Olson CR: Is there a 'consolida-tion' effect for monocular deprivation? Nature 282:404, 1979.12. Hubel DH and Wiesel TN: Receptive fields, binocu-lar interaction and functional architecture in thecat's visual cortex. J Physiol 160:106, 1962.13. Olson CR and Freeman RD: Cumulative effect ofbrief daily periods of monocular vision on kittenstriate cortex. Exp Brain Res 38:53, 1980.Aging and low-contrast vision: face percep-tion. CYNTHIA OWSLEY, ROBERT SEKULER,AND CULVER BOLDT.Previous work showed that despite good visual acuity,many healthy older people require more contrast to seegratings of low and intermediate spatial frequencies thando younger observers. Here we report that a daily per-ceptual activity, which relies on lower spatial frequencyinformation, is also adversely affected: as compared toyoung individuals, many older individuals require morecontrast to detect a face and to discriminate between twofaces. Ocular pathology, optical changes within theeyeball, and variation in criterion are tided out as expla-nations for the age-related elevation in threshold.Lower spatial frequencies carry informationsufficient for many routine perceptual activitiessuch as face perception, separation of figure fromground, and visual stabilization of posture.1' 2 Atlow contrasts, lower frequencies are particularlyimportant because the fine details of a target (highspatial frequencies) become invisible.3 As a result,in a low-contrast environment the perception ofobjects depends crucially on detecting more globalfeatures (low and intermediate frequencies). Ourprevious work indicates that many older individualsrequire higher contrast to see sinusoidal gratings oflow and intermediate frequencies than do youngerindividuals.4 6 Therefore low-contrast conditionscould pose a special problem for the elderly, forc-ing them to rely on visual mechanisms specializedfor processing lower spatial frequencies, preciselythose mechanisms of diminished sensitivity. Herewe explore this possibility by examining the effectsof contrast reduction on face perception for youngand old observers.Materials and methods. We tested two groupsof observers: 14 young observers (mean age =20.5; S.D. = 1.9) and 13 older observers (meanage = 74.2; S.D. = 4.1). Young observers werestudent volunteers whose most recent eye exams(on average, 10 months before our tests) revealedno ocular pathological conditions. Older observerswere healthy active individuals recruited from asenior citizen meeting center. Detailed ophthal-mological exams of the older observers of our ex-periment within 3 months were generally unre-markable. Most older subjects had traces ofcataract; three had early senile macular degenera-tion (SMD); all had intraocular pressures withinthe normal range (mean = 16.3 mm Hg; S.D. =3.2). All older observers had normal visual fieldswhen tested with a 1 mm diameter white target ona tangent screen.Observers' acuities were measured at a distanceof 3 in with a Sloan letter chart (120 cd/m2). Sinceall subsequent testing was done with binocularviewing, we report only binocular acuities here.Observers wore appropriate corrections duringthe experiment, their own spectacles or contactlenses or lenses in trial frames. Expressed as min-imum angle resolvable, acuities were 0.84 min arcfor young observers (S.D. = 0.10) and 0.94 minarc for older observers (S.D. = 0.17). Included inthe mean for the older group are the acuities forthe three observers with early SMD: 1.09, 1.04,and 1.02 min arc.The face perception task was divided into twoparts, detection and discrimination. To measuredetection, eight slides of single faces were rear-projected one at a time onto a translucent screen115 cm from the subject. Faces were relativelylarge targets, subtending a visual angle of approx-imately 5 X 7.4 degrees. The faces were ofmiddle-aged, Caucasian males having no beards,moustaches, eyeglasses, or unusual hairstyles. Allmales who were photographed wore a gray clotharound their shoulders to prevent the observerfrom making discriminations based on apparel.Our apparatus consisted of two matched slideprojectors positioned so that their beams coin-cided on the rear-projection screen. Fixed linearpolarizers positioned in front of each projector0146-0404/81/080362+04$00.40/0 © 1981 Assoc. for Res. in Vis. and Ophthal., Inc.Volume 21Number 2Reports 363produced orthogonal planes of polarization. Oneprojector contained a slide of the target face; theother had a fully opened aperture but no slide. Avariable polarizer controlled the contrast of theimage on the screen. When light on the screencame only from the projector with the slide, con-trast was maximum; when light on the screencame only from the projector with no slide, con-trast was zero. Thus the orientation of t h e polarizerdetermined the contrast level of the projectedface. Contrast is defined as the difference betweenmaximum and minimum luminances divided bythe sum of the two. The system was balanced withneutral-density filters, permitting contrast to bevaried with minimal variation in average lumi-nance. Mean luminance of the screen when a slidewas projected was 17.2 cd/m2.In the detection task, each slide was initiallypresented at zero contrast. Using a remote con-troller, the observer increased the contrast of thetarget until "something could just barely be seenon the projection screen." At the end of each trial,the experimenter recorded the orientation of thepolarizer, reset the orientation to one that yieldedzero contrast, and presented the next slide. Theorder of slides was randomized across subjects.In the discrimination task 16