Table 2.

Response rates in Experiment 2. Crowded. Similar or dissimilar

	Identical Trial	Similar Trial	Dissimilar Trial
Target	88% ± 1%	23% ± 7%	47% ± 4%
Flanker	n/a	60% ± 6%	24% ± 1%
Absent	12% ± 1%	17% ± 1%	29% ± 4%
Total	100%	100%	100%

Experiment 2: Average ( ± standard error across 2 observers) frequency of the three kinds of responses produced by the observer when asked to identify a crowded target: the target, the flanker, or an absent letter (neither target nor flanker). The stimulus was a target between two identical flankers. On each trial, the target and flanker were independent random samples from the same six-letter alphabet: L T I N M W. The three types of trials were flanker identical to target (e.g., WWW; 17% of trials), similar to target (MWM; 33%), and dissimilar to target (LWL; 50%). Substitution can account for, at most, 57% of the trials that produced these results (see the Results section and the Appendix, Eq. 7).