Acquiring the Mental Lexicon Through Sensorimotor Category Learning

Abstract

We report the electrophysiological correlates of learning a new category through either direct sensorimotor experience (E) or verbal definition (V). (1) Ss who successfully learned to categorize and name via E all showed an increasing late positivity in their ERPs; Ss who failed to learn did not. (2) All successful E learners could also state the rule verbally; nonlearners could not. (3) The increasing late positivity began to appear and increase only beginning with those trials in which the learners had discovered and could state the rule verbally. (4) When the nonlearners were told the rule verbally in a second phase of training (V), thereby making them able to categorize and name, they too displayed the late ERP positivity. (5) The positivity was present once the rule was told to the Ss, even if the subsequent training was without feedback, whether their training trials were easy or difficult, and even when Ss failed to categorize correctly; surprisingly, the positivity was there even when categorization was impossible (i.e., the rule did not distinguish the textures). (6) Ss thought they were not doing too badly even in the impossible condition, and even when they were given feedback indicating they were performing at chance level (50%). (7) An early ERP negativity emerged in Ss who were given false positive feedback (80%) under the impossible condition. We conclude that learners, whether they learned from experience or from a verbal definition, apply the rule mentally, and mental rule application is what the late ERP positivity reflects