Categorization Method Affects the Typicality Effect: ERP Evidence from a Category-Inference Task

Abstract

The typicality effect during categorization describes a phenomenon whereby typical items are more easily judged as members of a category than atypical items. Prior studies of the typicality effect have often used an inclusion task, which asks participants to assess whether an item belongs to a category. However, the correct exclusion of non-members is also an important component of effective categorization, which has yet to be directly investigated. Thus, the present study investigated how categorization method (inclusion vs. exclusion) modulates the typicality effect via behavioral and electrophysiological measures. Thirty-two participants (16 in the inclusion and 16 in the exclusion group) were shown six consecutive words that all shared one feature. Then, a seventh word was presented. The inclusion group judged whether the seventh word also possessed the feature, whereas the exclusion group judged whether the word did not possess the feature. The seventh word could be typical, atypical, or a nonmember of the category. Behavioral and event-related potential (ERP) data were collected. Behavioral results showed that the two groups did not differ in accuracy. However, typical items elicited shorter response times than atypical items, and this effect was more pronounced in the inclusion than the exclusion group. With regard to ERPs, interactions between item type and group were shown for the P2, N2, and N400 periods. Within the inclusion group, a typicality effect (indicated by a main effect of item type) was present in the P2 and N400 time windows, while the exclusion group elicited a typicality effect only in the N2 time window. These results provide electrophysiological evidence that an inclusion judgment task is more sensitive to category typicality than is an exclusion task.

Inductive reasoning differs between taxonomic and thematic contexts: Electrophysiological evidence

“…Taxonomic-based inductive reasoning elicited a larger P2 amplitude than thematic trials. The P2 is generally associated with allocation of attention [2,7,42], perceptual encoding [14,30,35,55], and early semantic processes [28,40]. In the present study, the effect of context on the P2 component might be related to the earlier process of relation encoding [30].…”

How types of premises modulate the typicality effect in category-based induction: diverging evidence from the P2, P3, and LPC effects

“…Specifically, after being presented with six consecutive words that shared one feature, participants were required to judge whether the seventh word also possessed that feature ( i.e ., inclusion), or whether it did not. They found that a larger P2 and smaller N400 were elicited by typical members relative to atypical members in inclusion, whereas typical members elicited a larger N2 than atypical members in the exclusion15. These results further indicated that the typicality effect has a pervasive influence on the early perceptual and attention processes, as well as later semantic processes and categorisation.…”

“…Based on previous studies, short RTs and higher “strong” responses should be found for typical conclusions relative to atypical conclusions19. In the field of ERP study, typicality has a pervasive influence on category-based verification and reasoning, which reflects on early N1 and P2 effects related to perceptual and attention processes, and later P3 or N400 effects related to semantic processes and categorisation6101115. Accordingly, significant differences in the ERP indices should be found between typical and atypical members.…”

“…For example, when participants were required to decide whether, or not, an incoming stimulus (conclusion) had the property described in the category presented before (premise), reaction time data revealed a significant typicality effect, and ERP data indicated that larger N1, P2, and N400 amplitudes were elicited by atypical words relative to typical words6. Recently, Wang and colleagues15 explored the typicality effect via different a categorisation method: that of either inclusion or exclusion. Specifically, after being presented with six consecutive words that shared one feature, participants were required to judge whether the seventh word also possessed that feature ( i.e ., inclusion), or whether it did not.…”

“…mainly explored the typicality effect during category-based deduction, in which the category in the premise included the category in the conclusion (e.g., Birds have property X; → Sparrows/penguins have property X; The bird includes the sparrow and penguin): as a result, the argument is logically valid161718, yet, little is known about the neural basis of the typicality effect during category-based induction, in which the category in the premise belongs to the category in the conclusion (e.g., Sparrows/penguins have property X; → Birds have property X), or both premise and conclusion belong to same basic level category (e.g., Sparrows/penguins have property X; → Chicken/crows have property X; Both of them are birds). Furthermore, the method in Wang et al 15. was also different from category-based induction in essence.…”