A 1-year-old likes to pull his cat's tail because the cat meows and moves away. One day he pulls another cat's tail and gets scratched. From that day on, he is cautious around cats. What cognitive process has probably occurred?

Accommodation: This process refers to people altering their existing schemas or creating new ones as a result of new learning. This usually happens because of new experiences that contradict the existing previous schemes.
Assimilation: Is the process by which people fit in new information into already existing schemas, this process doesn't alter our interior schema but rather only adds new information to it.

In the question, the 1-year-old likes to pull his cat's tail, however one day he pulls a cat's tail and gets scratched. This way, the kid had a new experience that didn't fit in the schema he already had about cats meowing when someone pulls their tails. Therefore, he had to modify his schemas to include this new information and it lead to a process of learning. This whole process he had in his mind (and why now he is cautious around cats) was due to accommodation.