It depends on the animal. And some are closer to adult human thinking capabilities than others. Even children have limited thinking capacity. Below a certain age, they literally have no episodic memory. To be brief, episodic memories are what we typically conceive memories as being. It's a when the brain replays events in your head to the best of its ability (which is very flawed, BTW). In contrast, there is also semantic memory, which is basically just a collection of facts. Toddlers might remember that throwing a toy on the floor will result in someone picking it up and returning it to you (a child's version of playing fetch with the adults), but they will not have any specific memories of times when this trick has actually worked. I suspect most mammals have semantic memory, but lack episodic memory. Some animals have an impressive amount of brain power, however. I'm sure most of you are familiar with Koko, the gorilla who learned to speak sign language. Koko, while not as intelligent as an adult human, was definitely capable of thought. This shouldn't really be a surprise, though, given they are somewhat close relatives of ours.
