Table 1.

Response rates in Experiment 1: Crowded. Similar and dissimilar

	Average	J.F.	R.C.	A.W.
Target	32% ± 4%	25%	32%	38%
Similar flanker	23% ± 3%	27%	25%	16%
Dissimilar flanker	9% ± 1%	12%	9%	7%
Absent letter	36% ± 1%	36%	34%	39%
Total	100%	100%	100%	100%

Experiment 1: Average ( ± standard error across 3 observers) and individual frequency of the four kinds of responses produced by the observer when asked to identify a crowded target: the target, the similar flanker, the dissimilar flanker, or an absent letter (neither target nor flanker). The stimulus was a target flanked by a similar and a dissimilar letter, one on either side, such as CGE. Percentages are rounded to the nearest integer. Where necessary, rounding is adjusted to ensure that the percentages for the four different types of responses add up to 100%. These data reject flanker substitution as a complete explanation. As part of a mixture model, a flanker substitution process can account for, at most, 55% of the trials that produced these results (see the Results section and the Appendix, Eq. 4).