Final answer:
A social learning theorist would interpret Dave's behavior as a result of vicarious learning, where he observed the consequences of his brother's actions and decided not to climb the brittle tree to avoid a similar fate.
Step-by-step explanation:
A social learning theorist would describe Dave's behavior as having learned vicariously through his brother's experience. Albert Bandura's social learning theory posits that individuals learn behaviors through the observational learning process. This involves watching someone else's actions and the consequences of those actions, and then using this information to guide one's own behavior. Seeing his brother fall and break his leg after climbing the brittle tree provides direct evidence to Dave that climbing the tree has negative consequences. Hence, he learns to avoid climbing the brittle tree without having to experience the painful consequence himself.