Final answer:
Extrinsic rewards can undermine learning in some instances by decreasing intrinsic motivation, which is supported by research including the overjustification effect and various studies on motivation dynamics, affirming that the answer is a. True.
Step-by-step explanation:
The concept of extrinsic rewards undermining intrinsic motivation in learning is known as the overjustification effect. Studies by Deci et al. (1999) have shown that while tangible rewards such as money can lead to a decrease in intrinsic motivation, intangible rewards like praise might not have such a detrimental effect, or may even enhance intrinsic motivation. The expectancy of rewards plays a significant role in this dynamic--anticipated rewards tend to decrease intrinsic motivation, whereas unexpected rewards may leave it unchanged or even increased. Adding to this complexity, the nature of the learning environment and the type of reinforcement can influence a student's internal motivation. For example, in a supportive and respectful classroom environment that fosters autonomy and provides rational for learning tasks, intrinsic motivation is likely to be sustained or enhanced, as suggested by Niemiec & Ryan (2009).
Considering all these factors, it is clear that extrinsic rewards can sometimes undermine learning by diminishing intrinsic motivation, though whether they do so depends on a variety of circumstances, such as the type of reward, whether it is expected, and the learning environment. Therefore, the final answer to whether extrinsic rewards can undermine learning in some instances is a. True, supported by extensive research confirming the nuanced relationship between extrinsic and intrinsic motivation.