Presuppositions vs. Asserted Content in Online Processing Florian Schwarz Abstract We report two experiments that investigate the time-course of the online interpretation of the presupposition of also, first relative to a control, and secondly relative to asserted content, namely the exclusivity of only, using the visual world paradigm. Both studies reveal rapid shifts in fixations to target pictures based on the presupposition expressed by also, within 400ms after its onset. In contrast, the as- serted exclusivity introduced by only arises roughly 400ms later, suggesting that - if anything - presupposed content is evaluated prior to asserted content. This is as ex- pected on semantic accounts of presuppositions, which see them as preconditions on interpreting the sentence in the first place, but somewhat surprising (though not nec- essarily strictly inconsistent) with pragmatic accounts that derive presuppositions via conversational reasoning, which has been found to require additional processing time in the case of scalar implicature computation. 1 Introduction An early and crucial insight in the modern study of linguistic meaning is that what speakers and hearers generally seem to perceive as the overall conveyed meaning of a given utterance should be broken down theoretically into distinct components. The motivation for this is that upon closer inspection, they can be differentiated by their role in utterances in general as well as their behavior in different linguistic en- vironments. To account for these differences, theorists generally appeal to distinct underlying mechanisms that give rise to these various aspects of meaning as well as to differences in how they affect the computation of the overall conveyed mean- ing of a complex utterance. Put very briefly, the literal, truth-conditional content of the lexical items in a sentence together with the structure they appear in is the Florian Schwarz Department of Linguistics, University of Pennsylvania, 619 Williams Hall, 255 S. 36th Street, Philadelphia, PA 19104, e-mail: florians@ling.upenn.edu 1 Draft, Fall 2013. Submitted for inclusion in: Schwarz, Florian (ed.) Under Contract. Experimental Perspectives on Presuppositions, edited volume for Springer’s Studies in Theoretical Psycholinguistics Series.