Step 1: Understanding the Question:
We must name the person behind the idea of cognitive dissonance, a well-known theory about attitude change.
Step 2: Link each name to a famous work.
Heider is tied to balance theory. LaPiere is tied to the study of attitude versus behaviour. Tajfel and Turner are tied to social identity. Festinger is tied to dissonance.
Step 3: Think about the theory itself.
The theory says that holding two inconsistent cognitions creates tension. People then try to reduce that tension by changing one belief or action. This is the work of Festinger, published in 1957.
Step 4: Remove the other names.
Options (2), (3) and (4) belong to other theories, so they cannot be the answer.
Step 5: Confirm the answer.
Option (1), Leon Festinger, is the match.
Step 6: Quick memory aid.
Link the theory to its name: dissonance means clash, and Festinger is the psychologist who studied what people do when their thoughts and actions clash. Keeping this pairing in mind avoids mixing it with Heider's balance theory.
Final Answer:
The correct name is Leon Festinger, option (1).