Stereoscopic processing of horizontal and vertical disparities was ass
essed by measuring how the stereoscopic appearance of test dots near t
he fixation point was influenced by inducing stimuli in the near perip
hery. The inducing stimuli were differentially magnified in the two ey
es and varied in horizontal eccentricity. As expected, when the induce
rs were horizontally magnified, the test dots exhibited depth contrast
, slanting in depth in a direction opposite the slant of the inducing
dots. When the inducers were vertically magnified, the test dots slant
ed in depth around a vertical axis toward the eye with the larger vert
ical image (the induced-size effect). However, two lines of evidence s
uggested that an eccentricity-dependent weighted average of horizontal
and vertical components of inducer-dot magnification determined the s
lant of the test dots. First, as the horizontal eccentricity of the in
ducing dots was varied, the trend of test-dot slants measured with ver
tical inducer magnifications was predicted by the trend of test-dot sl
ants measured with horizontal inducer magnifications. Second, test-dot
slants measured with a combination of both horizontal and vertical in
ducer magnification could be predicted by simply adding test-dot slant
s measured with either horizontal or vertical inducer magnification al
one.