Step 1: Idea: look at the key words.
The question speaks about how we perceive ourselves and what ideas we hold about our traits. These are words about a mental picture of the self.
Step 2: Word-meaning test for option (1).
Esteem means worth or value. Self-esteem is therefore about how much we value ourselves, not what we think we are like. It does not fit.
Step 3: Word-meaning test for option (2).
Concept means an idea or mental picture. Self-concept is the idea we hold about ourselves, including our competencies and attributes. It fits perfectly.
Step 4: Word-meaning test for option (3).
Efficacy means the power to produce an effect. Self-efficacy is the belief in our power to act well in a situation. It is about capability in action, so it does not fit.
Step 5: Word-meaning test for option (4).
Reinforcement means strengthening a behaviour with a reward. Self-reinforcement is giving oneself a reward. It does not fit.
Step 6: Conclusion.
Only self-concept refers to the overall idea of oneself.
Final Answer:
The blank is filled by self-concept, option (2).
\[ \boxed{\text{Self-concept}} \]