Final answer:
The conditioned stimulus in Gavin's scenario is the sight of boats, which now triggers seasickness due to his past experience with seasickness while deep-sea fishing.
Step-by-step explanation:
Gavin recently went deep-sea fishing and now experiences queasiness at the sight of boats due to a conditioned response linked to his past seasickness. In this scenario, the conditioned stimulus is the sight of boats. The process Gavin is experiencing is known as classical conditioning, a learning process first described by Ivan Pavlov. In classical conditioning, a neutral stimulus that initially does not cause a relevant automatic or natural response eventually comes to trigger a response due to its association with an unconditioned stimulus. In Gavin's case, boats were once a neutral stimulus, but after his negative experience, seeing boats now triggers seasickness.