Experiment 2 yielded overall lower error rates and shorter RTs than
Experiment 1 but the general pattern of results was replicated. As in
Experiment 1, observers' naming performance was worse for images whose contours were interrupted with segments of the same local contrast that formed L-vertices (
Figure 7). Observers made more errors when the segments were of the same local contrast polarity than when they were of different contrast polarity,
F(1, 54) = 17.7,
p < 1 × 10
−4,
η2p = 0.25. Post hoc
t tests revealed that the error rates for same-contrast L-vertices were reliably greater than different-contrast L-vertices,
t(54) = 3.55,
p < 0.001, Cohen's
d = 0.48, but same-contrast T-vertices were not reliably greater than different-contrast T- vertices,
t(54) = 1.50,
p = 0.14, Cohen's
d = 0.20. Importantly, the reduction in error rates and RTs with L-vertices with different (vs. same) contrast polarity was apparent even with the elimination of a global luminance separation strategy that could have been employed in
Experiment 1. Overall, observers made more errors when the segments formed L-vertices than when they formed T-vertices,
F(1, 54) = 13.3,
p < 6 × 10
−4,
η2p = 0.20, and although it was in the same direction as in
Experiment 1, the interaction between contrast polarity and vertex type fell short of significance,
F(1, 54) = 1.91,
p = 0.17,
η2p = 0.034. The main effects of segment polarity and of vertex type were also significant for RTs,
F(1, 54) = 4.65,
p < 0.04,
η2p = 0.079, and
F(1, 54) = 4.51,
p < 0.04,
η2p = 0.077, respectively, suggesting that there was no speed–accuracy tradeoff. The interaction of segment polarity and vertex type for RTs did not reach significance although it was in the same direction as in
Experiment 1 which is what would be expected from same polarity L-vertices producing greater difficulty in object naming than different polarity L-vertices.