Ian's parents have noted that he studies longer and gets better grades when they and the teacher praise his efforts and accomplishments than when they simply acknowledge his good performance. This pattern suggests that Ian is motivated primarily by

Extrinsic motivation

Explanation:

Extrinsic Motivation

This is simply known as the act of engaging in an activity or doing something due to the fact that there is an external reward or to avoid punishment.  it simply means that individuals shows the desired behavior in order to gain an external reward. Ian's behavior in this case clearly shows that he is extrinsically motivated. example of this extrinsic behavior is when an individual is studying because you need good grades, writing to publish a novel etc.

It is also regarded as a behavior that is environmentally motivated or created reason such as incentives or consequences to engage in a said activity.

answer; john stuart mill's principle of utility is your answer; /// good luck

answer; correlational;