Although binocular retinal disparity is important information for human depth perception, perceived depth is sometimes in the opposite direction to the geometrical prediction (depth reversal). In the present study, binocular disparity modulated sinusoidally along a horizontal meridian was introduced into a random-dot stereogram and apparent depth direction was measured as a function of spatial frequency, number of cycles, and amplitude of disparity modulation. The spatial frequency of disparity modulation was either 0.1, 0.2, or 0.4 cpd. The number of cycles ranged from 1 to 8. The amplitude of disparity modulation was up to 0.5 deg. Five of six observers reported reversed depth in the condition with the highest spatial frequency and larger stimulus size. Two observers also reported reversed depth in the condition with the lower spatial frequency and the smallest stimulus size. It appears that multiple factors contribute depth reversal.%両眼網膜像差は人間にとって有効な奥行き手がかりであるが，知覚される奥行きが幾何学的な予想と反対になる場合があることが知られている（奥行き反転）．ここでは，ランダムドットに水平方向の正弦波状の網膜像差変調を与え，知覚される奥行きの方向と空間周波数および周期数の関係を明らかにした．空間周波数は0．1，0．2，もしくは0．4cpdであった．周期数は1～8であった．網膜像差の振幅は最大0．5degの範囲まで変化させた．6名のうち5名の被験者は高空間周波数で周期数が大きい条件で反対の奥行きを報告した．2名の被験者は低空間周波数で周期数が小さい条件で反対の奥行きを報告した．これは複数の要因が奥行き反転に寄与することを示している．
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