The experimental study of artificial language learning has become a widely used means of investigating the predictions of theories of phonology and of learning. Although much is now known about the generalizations that learners make from various kinds of data, relatively little is known about how those generalizations are cognitively encoded. Models of phonological knowledge fall into two broad classes: lexical (analogical) vs. abstract (grammatical). This paper provides evidence that generalizations acquired in the lab can be encoded at an abstract level, based on an ERP study of brain responses to violations of lab-learned phonotactics. Novel words that violated a learned phonotactic constraint elicited a larger Late Positive Component (LPC) than novel words that satisfied it. This constitutes evidence for the abstractness of the encoded generalization in that the LPC is also associated with syntactic violations and with violations of musical structure. The LPC has also been found in the study of naturalistically learned phonotactics, providing support for the ecological validity of lab learning of phonology.