The Time Course of Negative Priming

Doctoral Thesis / Dissertation from the year 2009 in the subject Psychology - Cognition, grade: magna cum laude, University of Göttingen (Institute for Nonlinear Dynamics), language: English, abstract: Selective attention enables goal-directed behavior despite the permanent, immense input to the sensory system. Contradicting early speculations of an active attending and passive ignoring, the active nature of ignoring was revealed by the negative priming paradigm. The present thesis will describe our multi-level approach to reveal the temporal structure of negative priming. Accompanied by computational modeling, we run sophisticated psychological experiments and record and analyze EEG data.

The common denominator of all negative priming paradigms is the simultaneous presentation of targets that have to be attended to, and distractors that are to be ignored. A slowdown in the response to a formerly ignored stimulus is labeled negative priming. Because of negative priming being robust and sensitive at the same time, a variety of different theoretical accounts have been developed. But until now none of the theoretical accounts is able to explain all aspects of the negative priming effect. In order to clarify the situation, the time course of negative priming is crucial. In order to advance the debate on theoretical accounts, we build a computational model comprising most of the mechanisms suspected to play a role in negative priming tasks. The outcome is not only a meta-model for negative priming, but in itself a simplified model of the brain as a framework for action selection based on perception. We address the tradeoff between biological realism and understandability by modeling each assumed mechanism separately but keeping the internal dynamics of each of the corresponding layers very simple.

The computational implementation of theories is accompanied by a series of behavioral experiments intended to decide about the temporal localization of the negative priming effect relative to the processing of a single trial. We present an EEG experiment that replicates findings from one of the few studies on event-related potentials related to negative priming. To access the timing of the effect not only through brain recordings but behavioral measures, we design a paradigm which divides stimulus identification and target selection. The results locate negative priming also in the latter part of a trial. This remainder of a trial still contains both target selection and response generation. Therefore, another trial splitting paradigm singles out the response generation phase. We finally find the devotion of negative priming to the target selection phase.