Figure 2.

Example of test stimuli. Four types of test stimuli were used, as exemplified here: complete items (A) that contained all the labeled features from the training set, items that were missing one learned feature (B and C), and items in which two features were missing and/or altered (D). Items B and C are further differentiated into missing-essential-feature (C for the alpha description and B for the beta description) and missing-nonessential-feature (B for the alpha description and C for the beta description) conditions. no stimuli from the training set were also used as test items.