Date on Senior Honors Thesis

5-2026

Document Type

Senior Thesis

Degree Name

B.S.

Department

Psychological and Brain Sciences

Committee Chair

Nelleke Van Wouwe

Committee Member

Dr. Joseph Neimat

Committee Member

Mark Running

Author's Keywords

Valence; Simon Task; EAST; Spatial Simon Task; Action Control; Emotion

Abstract

People adjust their thoughts and actions in response to a changing environment every day and emotions may influence these actions. Understanding how emotion impacts action control in situations where emotion is central to the action (task-relevant) compared to when it is present in the environment as distracting information (task-irrelevant) is essential. Currently it is unclear when emotion most significantly modulates action control. This study seeks to compare how valence (positive versus negative emotion) impacts action control performance when valence is task-relevant and task-irrelevant by using two modified versions of the Simon conflict task.

The Simon task is a paradigm to study response conflict by creating interference between a presented stimulus and a subsequent action response. Participants are instructed to respond to a lateralized stimulus on the screen. When the location of the stimulus conflicts with the trained response, this slows reaction times and reduces accuracy compared to when they do not conflict (Simon effect). We created two modified versions of the Simon task and used happy and angry faces as valenced task stimuli. The spatial affective Simon task (ST), participants were instructed to respond to the emotional expression of a face (valence is task-relevant). In the extrinsic affective Simon task (EAST), the affective stimulus was a face with an emotional expression, but participants were instructed to respond to the color of the face (valence is task-irrelevant). We collected reaction times and accuracy rates for each task in 12 healthy participants.

Valence did not significantly impact the Simon effect in either task and we did not find a significant Simon conflict effect in the EAST. However, the spatial task did show a significant conflict effect with slower and less accurate responses on conflict trials. Future studies will test alternative modifications to this paradigm’s design to study how emotion could play a role in action control and motor response. Such knowledge will allow these tasks to be translated in clinical research in studying specific brain regions and their role in processing emotional stimuli in conflict response settings.

Additional Files
Aleissa_Yaara Thesis Proposal .pdf (269 kB)
Revised Submission

Lay Summary

            Every day, people must quickly decide how to act in response to what they see around them. Emotions in the environment, such as a happy or angry face, may influence how easily people make decisions. However, scientists still do not fully understand when emotions affect our actions the most. This study examined whether emotions influence how people control their actions when the emotional information is important to the task compared to when it is used as a distraction. To test this, participants completed two computer-based tasks that measure how quickly and accurately people respond to visual information.

In one task, participants were asked to respond directly to the emotion shown on a face (happy or angry). In the other task, participants responded to the color of the face and were instructed to ignore the emotional expression. In the second task, the emotional faces sometimes appeared on the same side of the screen as the correct response and sometimes on the opposite side. When the location of the face conflicted with the correct response, participants’ reactions tended to be slower or less accurate. The results showed that emotional expressions themselves did not strongly change how people handled this type of response conflict. However, participants were slower and less accurate when the location of the stimulus conflicted with the correct response in the task where they were responding to the emotion of the face.

Future research will continue to explore how emotions influence decision-making and action control. Understanding these processes could help researchers use similar tasks to study how the brain processes emotional information and controls behavior, which may be useful for studying certain neurological or psychological conditions.

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