Figure 6.

Psychophysical results. A, Accuracy was successfully equated across attention conditions for the first six pedestal contrast levels by systematically changing Δc. Subjects performed poorly for the target of the highest contrast as we could not make Δc large enough at this pedestal (unconnected circles at 81.13% contrast). Thus, we focused the behavioral analysis on the first six pedestal contrast levels. B, Psychophysical contrast discrimination thresholds at different pedestal contrast levels across focused-attention (blue circles) and divided-attention conditions (green circles). Smooth curves represent the fits of the TvC functions using a combination of signal detection theory (Eq. 1) and a Naka-Rushton equation (Eq. 2). Focused attention reduced discrimination thresholds, leading to a downward shift of the TvC. In turn, this downward shift in the TvC curve is consistent with a change in the multiplicative response gain parameter or the slope of the underlying CRF. Error bars in all figures indicate ±SEM across subjects.