The Role of Low-Level Visual Features in the Emotional and Motivational Relevance of Symbolic Stimuli
Doctoral thesis
Date of Examination:2023-12-18
Date of issue:2024-07-16
Advisor:Prof. Dr. Annekathrin Schacht
Referee:Prof. Dr. Annekathrin Schacht
Referee:Dr. Arezoo Pooresmaeili
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Description:Dissertation
Abstract
English
In our daily lives, we encounter a wide range of visual stimuli, but printed words are critical for communication and information acquisition. Emotional words receive preferential attention, resulting in modulations of behavioral and neural responses at various stages of stimulus processing. The extraction of the emotional connotation of a word necessitates access to its semantic content. Nevertheless, emotional effects of words are observed also at early visual processing stages, prior to full semantic access. These early effects are proposed to result from the association of emotional relevance to the low-level visual features of words, based on repeated simultaneous exposure to the word’s visual form and semantic content. This dissertation presents a series of studies that used behavioral and event-related brain potential (ERP) measures to investigate the associative mechanisms by which low-level visual features of words affect their emotional relevance. Three key research questions were addressed: First, to define the precise role of low-level visual features in relevance acquisition; second, to characterize the neural and behavioral response dynamics during this acquisition; and third, to assess the impact of the acquired relevance on word memory. Study 1 and Study 2 used word-like stimuli that acquired relevance via associative learning. Different dimensions of low-level visual features such as characters and font type were manipulated during the learning and subsequent test sessions to investigate their contribution to the relevance acquisition process. Relevance effects on early perceptual processing (P1) appeared contingent on the dimension of low-level visual features involved in the association (Study 2). Both studies showed for the first time that symbolic stimuli of associated relevance, similar to emotional words, automatically capture attention as reflected in EPN modulations. However, in contrast to earlier stages of perceptual processing, these EPN modulations were insensitive to the manipulation of low-level visual features (Study 1). Relevance effects on higher-level stimulus evaluation (P300/LPC) linearly increased during relevance acquisition (Study 2). Positive relevance had a greater impact on later stages of stimulus processing compared to negative relevance, mirrored behaviorally by faster learning of positive associations. Study 3 explored how relevance association to various dimensions of low-level visual features affected memory-related neural processing. Positive relevance influenced old/new ERP responses in the P300/LPC time window, regardless of the dimension of low-level visual features it was associated with. However, the advantage of memory-related processing by positive relevance disappeared when the association was no longer necessary for task completion. This work contributes to the understanding of the effects of emotional relevance on behavioral and neural responses to words and provides new insights into the role of low-level visual features in this process.
Keywords: Emotional relevance; Associative learning; Visual word processing; Low-level visual features; Event-related potentials