analyse change with age. This series may form the basis for assessment of contrast sensitivity in children. Materials and methodsCaucasian children aged 3 to 15 years and adults 18 to 29 years were subjects in this study. In each age group approximately equal numbers of males and females were tested. All subjects were volunteers. 86% of them were given an ophthalmological examination. Those over 6 years were required to have an uncorrected Snellen acuity of 6/6 or better for distance and those under 6 years an uncorrected acuity of 6/9 by the E test. The 14% not given an ophthalmological test were distributed over all age groups.Vertical sinusoidal gratings were generated in the conventional way2 on a display monitor (Tektronix 604 P31 fast-decay phosphor). The average luminance was 9 cd/M2 and varied from peak to trough between 14 cd/m and 4 cd/M2 giving a maximum contrast value of 0 5, contrast being defined as (Lmax -Lmin/Lmax + Lmin) whtr8-Lmax and Lmin are the maximum and minimum luminances respectively of the gratings display. Observers sat 1 metre from the display, which was viewed binocularly with natural pupils through a circular window mounted on the face of the monitor such that the display subtended 6 degrees. The surround was approximately matched for luminance and colour. Room luminance was approximately 2 cd/M2. An experimenter sat beside the subject and showed samples of gratings, varying the spatial frequency and contrast. The subject's task was to report when any lines were visible. Special care was taken to ensure the instructions were understood. Subjects were asked to keep their heads straight and at the measured distance; this was checked on a video-863 on 12 May 2018 by guest. Protected by copyright.

Birth patterns of non-aboriginal, first admission, Western Australian psychiatric patients born between 1920 and 1950 were compared statistically with those of the general population. Three I. C. D. categories were examined: schizophrenia, anxiety neurosis, and depressive neurosis. For both categories of neurosis no deviations from normal birth patterns were observed. For males, marked excesses in schizophrenic births were observed in June, and for females a similar excess occurred in September. Possible explanations for this sex difference are examined.

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This paper reports a simple low-cost computer peripheral for generation of gratings. Its advantages are minimal CPU operations, reliability, and variety of programmable output functions. The luminance gratings used in the study of human spatial and temporal vision can be generated in several ways. These include optical techniques (Antis & Comerford, 1975) and electronic waveform generators for the Y-axis and Z-axis (e.g., Fischer, 1976; Hughes & Snow, 1973; Shapley & Rossetto, 1976; Stamps & Bourne, 1972), coupled to a TV raster or cathode-ray oscilloscope (CRO) with a time base for the X-axis. Either analog (Rogers, 1976) or digital (Brown, 1977) techniques can be used to provide moving gratings. All the latter methods are related to the original technique described by Campbell and Green (1965). In addition, a microprocessor could be used as a scheduling device for switching peripheral generators (Keemink, van der Wildt, & Van Deursen, 1979). An alternative is to calculate the appropriate waveform for the Z-modulation profiles. Further, stimulus parameters can be preprogrammed. A microcomputerbased system reported by Fritsch and Keck (1978) uses the sequential digital-to-analog (0/A) output of a pre

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