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Abstract:
According to the central-peripheral dichotomy (CPD), feedback from higher to lower cortical areas
along the visual pathway to aid recognition is weaker in the more peripheral visual field. Metacontrast
masking is predominantly a reduced visibility of a brief target by a brief and spatially adjacent mask when the
mask succeeds rather than precedes or coincides with the target. If this masking works mainly by interfering
with the feedback mechanisms for target recognition, then, by the CPD, this masking should be weaker at
more peripheral visual locations. We extended the metacontrast masking at fovea by Enns and Di Lollo
(1997) to visual field eccentricities 1, 3, and 9 degrees. Relative to the target’s onset, the mask appeared at a
stimulus onset asynchrony (SOA) of -50, 0, 50, 92, or 142 milliseconds (ms). Enlarged stimuli were used for
larger eccentricities to equalize target discrimination performance across eccentricities as best as possible
for zero SOA and when SOA was too long for substantial masking. At each eccentricity, the masking was
weakest at 0 or -50 ms SOA, strongest at 50 ms SOA, and weakened with larger (positive) SOAs. Consistent
with the CPD, larger eccentricities presented weaker maskings at all non-zero, and particularly the positive, SOAs.
