Table 2.

Summary of most parsimonious model. Model estimates and 95% confidence intervals for the effects of chromatic distance and achromatic Michelson contrast between the stimuli and background. Increasing chromatic distance makes discrimination easier (i.e. a higher pass frequency in our experiments), while increasing background contrast makes discrimination more difficult (i.e. a lower pass frequency). We also include the marginal pseudo-R² calculated using the MuMIn package in R [2].

predictor	point estimate	95% CI lower bound	95% CI upper bound
chromatic distance***	0.538	0.478	0.598
background contrast**	−0.616	−1.025	−0.207

**p < 0.01; ***p < 0.001; marginal pseudo-R² = 0.161.