Processing ellipsis: electrophysiological signatures of retrieval and integration mechanisms

Elliptical sentences (e.g. "John threw the ball, and Sally too.") are recovered by a process of retrieving and integrating earlier mentioned information (here: "threw the ball"). Few event-related brain potentials (ERP) experiments on verb-gapping (e.g. "John threw the ball, and Sally the stick.") have reported a P600 component, being interpreted as a reflection of an integration process of a 'missing' verb and remnant object. An open question concerns the specific timing of retrieval of missing structure. As a means to further investigate retrieval mechanisms and to corroborate the component implicated in the integration process, we manipulated the structural size of antecedents in two ERP experiments. We used gapping and a sub-type of gapping, i.e. 'stripping' (cf. "and Sally too"), in Dutch. After onset of critical measure points (e.g. "too") we found - compared to control conditions - a positive deflection starting at 300 ms. We relate this to the onset of a retrieval mechanism, indicating that ellipsis resolution starts relatively early. Additionally, the amount and type of information to be integrated modulated the scalp topography and duration of the positivity. We conclude that an amalgam of positive deflections signifies a retrieval process that is directly followed by an integration mechanism.