Perceived similarity ratings predict generalization success after traditional category learning and a new paired-associate learning task

Abstract

The current study investigated category learning across two experiments using face-blend stimuli that formed face families controlled for within- and between-category similarity. Experiment 1 was a traditional feedback-based category-learning task, with three family names serving as category labels. In Experiment 2, the shared family name was encountered in the context of a face-full name paired-associate learning task, with a unique first name for each face. A subsequent test that required participants to categorize new faces from each family showed successful generalization in both experiments. Furthermore, perceived similarity ratings for pairs of faces were collected before and after learning, prior to generalization test. In Experiment 1, similarity ratings increased for faces within a family and decreased for faces that were physically similar but belonged to different families. In Experiment 2, overall similarity ratings decreased after learning, driven primarily by decreases for physically similar faces from different families. The post-learning category bias in similarity ratings was predictive of subsequent generalization success in both experiments. The results indicate that individuals formed generalizable category knowledge prior to an explicit demand to generalize and did so both when attention was directed towards category-relevant features (Experiment 1) and when attention was directed towards individuating faces within a family (Experiment 2). The results tie together research on category learning and categorical perception and extend them beyond a traditional category-learning task.

Keywords: Category learning; Memory generalization; Perceived similarity.

Figure 1.

Example face-blend stimuli. Parent faces on the leftmost side are designated “category relevant parents” as these parents determined family membership—Miller, Wilson, or Davis—during learning and generalization. Parent faces across the top are designated “category-irrelevant parents” as these parents introduced physical similarity across families but did not determine categories. Three category-irrelevant parents were used for learning. The rightmost three category-irrelevant parents are a subset of new faces used for generalization. Parent faces were never viewed by participants, only the resulting blended faces. The face blending procedure produced pairs of faces that shared a category-relevant parent and belonged to the same family (shared parent - same family name; example indicated with dark grey box), pairs of faces that shared a category-irrelevant parent and belonged to different families (shared parent- different family name; example indicated with medium grey box). Non-adjacent pairs did not share a parent and were not related (example indicated with light grey boxes).

Figure 2.

Top panel are results from the traditional category learning experiment. Bottom panel (shaded grey) are results from the face-name paired associate learning experiment. A & E. Average similarity ratings for faces that share a parent and family name, faces that only share a parent, and faces that don’t share any parents before learning. B & F. Average similarity ratings for the same pairwise comparisons after learning. Asterisk represents a significant (p < .05) difference in post-learning similarity ratings for faces that belong to the same family vs. faces that share physical similarity but belong to different families (i.e. a category bias in perception). C & G. Changes in similarity ratings from pre- to post-learning. Asterisk denotes significant (p < .05) increases and decreases in perceived similarity for faces. D & H. Positive relationship between indirect (category bias in perception) and direct (categorization accuracy for new faces) measures of memory generalization.