This Complete Evidence-based practice paper investigates students' perceptions regarding the presence of two extra credit (EC) modules on parallel computing topics in an introductory electrical and computer engineering course. Prior work investigating these EC modules showed a high participation rate (48-60%) across and high performance (80-88%) on the end-of-module EC quiz across three semesters [1]. The presence of extra credit has long been a topic of discussion in education, gaining strong arguments both for and against its inclusion in curriculum. Those opposed to extra credit cite ethical concerns related to grade inflation and question the utility of providing students with extra work that is not distributed as a traditional assignment. However, prior work has suggested that EC, when carefully designed, can have affordance such as motivating additional learning. This paper seeks to extend the previous, quantitative findings relating to these parallel computing EC modules by investigating students' motivations for completing or not completing the modules, as well as impacts on anxiety, effort, and learning. In doing so we seek to understand the affordances and drawbacks of extra credit in an effort to provide further insight into how to effectively design and deploy EC in introductory engineering courses.A survey, consisting of a mix of five-point Likert items and short answer questions, was distributed to a large introductory electrical and computer engineering course across two semesters gaining 105 responses. The Likert questions related to: 1) students' motivations for completing the extra credit, 2) perceived learning gains from extra credit opportunities, 3) interest generated in the topics EC assignments covered, and 4) the relationship between anxiety and the presence of EC in the course. Survey responses for a set of short answer questions were analyzed with multiple rounds of inductive coding. In cases where a large number of related codes emerged, axial coding methods were used to extract thematic groups.The following are results from the Likert questions and analysis of the corresponding short response questions. For those respondents who did complete the EC modules, the primary motivations they identified were: 1) maximizing their grade either by supplementing their current grade or protecting it from potential deductions in the future, 2) exploring new concepts, and 3) the approachability of the assessments due to their perceived low difficulty level and time requirements. Similarly, among those respondents who did not complete the EC modules, they stated a lack of time and no need for the extra points as the primary reasons.Students overwhelmingly indicated through their Likert responses that they were willing to put large amounts of effort into extra credit assignments even in cases where they were only worth a few points. When asked about the factors that influence that effort, responses expanded upon the notion of 'grade protection' with some responses indicating that, if the time and poin...