That we learn though the consequences of our behaviours
Positive reinforcement
By adding something pleasurable to the situation, the behaviour is strengthened.
Negative reinforcement
By taking something aversive from a situation, the behaviour is strengthened
Example of positive reinforcement
Praise or food if hungry
Example of negative reinforcement
Pain stops or anxiety lessons
Punishment
By taking something pleasurable from the situation or adding something aversive to the situation, behaviour is weakened
Punishment examples
pocket money taken away, physical punishment
Evaluation - Useful application
Training techniques - business incentives and disciplinarian. Our justice system! Token economies in prison ( rewards for good behaviours)
Evaluation - Deterministic

Skinner argued that free will was an 'illusion' and all influences are external e.g. your 'decisions' are always made based on the consequences and therefore behaviour is really determined by operant conditioning.