Jason just sat down to work on his term paper when his friends called and invited him to a party. if jason decides he will only go to the party after he finishes outlining the term paper, his decision reflects the functioning of his

his decision reflects the functioning of his Ego

Ego is a feeling of self-importance that derives from someone's sense of morality and obligation that could influence someone's action.

In this case, Jason sense of obligation towards his study prevent him from spending too much time at parties.