Presuppositions in Online Language Comprehension

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In interpreting linguistic utterances, the human mind has to piece together many different types of information. While this takes place sub-consciously, language researchers have developed theoretical perspectives on how distinct aspects of meaning are factored into the overall interpretation. However, little remains known about how these theoretical constructs relate to actual cognitive processes taking place in real-time. The present project will help to fill this gap by investigating aspects of meaning, specifically presuppositions, with experimental tools from psychology, and thereby deepen our understanding of a fundamental aspect of human interaction. This is essential for a comprehensive perspective on how speakers relate to the world through language, and also bears on broader issues in society. For example, research on the psychology of memory has shown that the presuppositional status of information has strong effects on memory accuracy, which is highly relevant in eye witness testimony and other related activities. With the support of the National Science Foundation, Dr. Schwarz will study how presuppositions relate to other aspects of meaning, such as asserted content and certain pragmatic inferences (specifically implicatures), using a variety of experimental methods. Presuppositions are backgrounded relative to the main point asserted by an utterance, and (typically) already count as established in the discourse. For example, 'again' in 'John left again' suggests that it was already known that John had left previously, the main news being his second departure. The project will investigate the relative time-course of these two aspects of meaning in online processing: Does the presupposition get evaluated first, suggesting that its role for the overall felicity of an utterance needs to be confirmed at the outset? Or does it play the role of an additional inference that is only considered later? Another crucial feature of presuppositions concerns their relation to operators like negation: 'John hasn't left again' still conveys that he left before (while denying a second departure). The project will investigate whether such embedded occurrences of presuppositional expressions introduce additional cognitive demands. Finally, the project will also study the availability and potential cognitive cost of an alternative interpretation of such sentences, as in 'John (certainly) hasn't left again--he never left in the first place!' The present project constitutes the first comprehensive attempt to use tools from experimental psycho-linguistics to study the cognitive processes involved in presupposition comprehension. Using an eye tracker, Dr. Schwarz will record people's eye movements relative to a visual scene while they're hearing linguistic stimuli that contain presuppositional expressions. This allows for real-time insights into the unfolding of individual aspects of the overall meaning with millisecond-accuracy. Response times and other behavioral measures further help to understand speakers' interpretation processes and preferences. By combining theoretical work with foundations in philosophy of language and formal semantics with experimental methods from psycho-linguistics, this interdisciplinary project will help to integrate the study of meaning in natural language more deeply into the cognitive sciences and advance our theoretical and empirical understanding of the human mind's remarkable capacities at work in linguistic communication.