Human Neuroscience

non-grammatical and after some time of exposure perform this categorization task with an accuracy greater than chance (Reber, 1967). The explanation of these learning effects in this and later work (Reber, 1989) was that participants acquired an abstract representation of the underlying rules (see also Opitz and Friederici, 2004, for a similar argument). A recently proposed theoretical account of category learning (Ashby and O’Brien, 2005) suggests that such rule sets are developed via a feedback-dependent, trial-and-error learning process. Indeed, increasing experimental evidence suggests that the development of an implicit rule set depends on reinforcement learning (RL): If people are not provided with explicit feedback, they do not learn the rules (e.g., Ashby et al., 1999). Furthermore, a recent study on L2 learning (Mueller et al., 2009) is also consistent with this proposal. In this study, the ERPs to auditorily presented correct and incorrect Italian sentences were compared in native and non-native speakers after brief exposure to correct Italian sentences of a similar structure without any feedback. Native speakers in this experiment exhibited an N400 followed by a P600 component in the ERP to incorrect sentences, indicating grammatical rule use (Hahne and Friederici, 1999; Kaan and Swaab, 2003; Hagoort, 2008). In contrast, non-native speakers did only show an N400. As no P600 to grammatical violations was observed, it can be inferred that non-native speakers did not acquire an abstract representation of the underlying syntactic rules after mere exposure to simple Italian sentences. From this it can be assumed that feedback is necessary for the acquisition of a grammatical rule set. Interestingly, some of the brain structures implicated by Ashby’s theory 2005 in feedback-based rule learning, e.g., the basal ganglia (BG) and the anterior cingulate cortex (ACC), are also thought to play an important role in RL (Montague et al., 1996; Holroyd