Social-comparative feedback (i.e., providing a learner with information regarding his/her performance relative to a group average) has been shown to influence a learner’s psychological and behavioural outcomes during motor skill acquisition (Avila, Chiviacowsky, Wulf, & Lewthwaite, 2012; Eliasz, 2012; Lewthwaite & Wulf, 2010; McKay, Lewthwaite, & Wulf, 2012; Stoate, Wulf, & Lewthwaite, 2012; Wulf, Chiviacowsky, & Cardozo, 2014; Wulf, Chiviacowsky, & Lewthwaite, 2010, 2012; Wulf & Lewthwaite, 2016). This research indicates that motor skill acquisition is facilitated when learners believe they are performing better than the average, regardless of their actual performance. It has been suggested (Wulf & Lewthwaite, 2016) that a better-than-average mindset enhances psychological factors such as self-efficacy and motivation and in turn, actual behaviour. However, there is also evidence to suggest that self-efficacy (having state-like properties) and motivation (having both state and trait-like properties) are related in terms of their affective influence on learning (Bandura, 1997; Schunk, 1990, 1991, 1995) but the relationship between the two constructs and its subsequent outcomes remain unclear. Even though individual differences in motivation have been suggested to influence self-efficacy beliefs, they have been largely ignored in this line of research. There is also evidence to suggest that learners possessing high levels of motivation (whether that may be at a trait or state level) may not interpret feedback in the same manner (Aronson, 1992; Festinger, 1957; Frey, 1986; Harmon-Jones, 2012; Harmon-Jones & Harmon-Jones, 2002; Harmon-Jones, Harmon-Jones, Fearn, Sigelman, & Johnson, 2008; Harmon-Jones & Mills, 1999; Harmon-Jones, Schmeichel, Inzlicht, & Harmon- Jones, 2011; Steele, 1988). Therefore, the goal of this dissertation is use both theoretical and applied perspectives to examine the degree to which social- comparative feedback affects psychological and behavioural outcomes in highly- motivated learners (e.g., medical trainees) learning procedural skills. Independent of actual performance, we provided manipulated feedback information to novice pre-clerkship medical trainees while they were learning motor skills to suggest that they were performing better or worse than the average. The first study used a basic sequential key-press learning task (Eliasz, 2012) and a basic suturing task to explore the role of social-comparative feedback in medical trainees and tested whether features of the task were important (i.e., basic laboratory task or technical skill task) during the interpretation of this feedback. The second study used the same experimental paradigm to extend our results to a relevant medical education context (i.e., medical trainees learning basic suturing techniques). The final study examined whether the credibility of the feedback provider (i.e., expert versus peer) played a role in how social-comparative feedback was being internalized by novice medical trainees. Our initial study demonstrated that, compared to those receiving positive or no social-comparative feedback, medical trainees receiving negative social- comparative feedback during motor skill acquisition had significant difficulties in learning both the laboratory and technical skill task. These findings suggested that compared to other learners, novice medical trainees (a subset of highly-motivated learners), responded differently to social-comparative feedback. The second study replicated this pattern and revealed that medical trainees receiving below-average feedback during technical skill acquisition experienced significant detriments to their performance, learning and self-efficacy. Our final study found that regardless of the feedback source (hypothetical expert versus another peer), the experience of receiving negative social-comparative feedback impacted self- reported psychological measures and the immediate performance of a basic surgical technique. This dissertation provides, to the best of our knowledge, the first demonstration that medical trainees, a subset of highly-motivated learners, interpret social-comparative feedback differently than other learners studied in the literature. More specifically, receiving positive social-comparative feedback did not facilitate the learning process as found in previous studies with non-medical learners, while the delivery of negative social-comparative feedback, irrespective of task or feedback provider, was psychologically and behaviourally detrimental to novice medical trainees learning motor skills. / Dissertation / Doctor of Philosophy (PhD) / This dissertation includes three original studies designed to examine the effects of social-comparative feedback during skill acquisition in highly- motivated learners (e.g., medical trainees). Regardless of actual task performance, novice medical trainees who were provided with feedback during the learning process indicating that they were performing worse than the group average, experienced significant detriments to their psychological and behavioural outcomes. This effect was present regardless of the task being learned (i.e., key- pressing or suturing) or who was delivering the feedback (i.e., a hypothetical ‘expert’ or ‘peer’). Receiving better-than-average feedback did not result in any additional psychological and behavioural benefits. Contrary to the research with non-medical students, where “you are above-average” social-comparative feedback facilitates learning and “you are below-average” social-comparative feedback is no different than a control condition, these studies suggest that the experience of receiving below-average feedback during the learning process can be detrimental for highly-motivated novice learners. These findings are important to consider in both the context of feedback delivery and remediation as they provide evidence that novice medical trainees, regardless of the task and feedback provider, experience difficulty in receiving information that they are performing relatively poorly compared to their peers.