Table 1.

Results from experiment 1

	One-choice (simple RT)		Two-choice
Difficulty	Proportion of black or white pixels	Mean RT (ms)	Proportion of black or white pixels	Proportion correct	Correct mean RT (ms)	Error mean RT (ms)
Difficult	0.56	949	0.52	0.76	852	932
Medium	0.59	571	0.54	0.89	765	877
Easy	0.62	477	0.56	0.94	692	767