No, animals cant think in “words” per se—unless by words you mean “language.”
“Can animals think in language” (at least in the limited sense we understand language) is a more complex version of this question, with a lot more potential answers.
Because animals lack the same complex vocal skills (such as muscle control over their tongues, ability to articulate and refine sounds into speech patterns) and generally have not evolved to develop any form of complex language structure (such as syntax or grammar) they are unable to communicate through words the way humans do. Animals are are, however, able to react physically, emote through facial expression and body language, remember previous events, dream, and—in some cases—even problem-solve. This varies from species to species of course. But all of these actions imply some form of cognizant thinking, reflection, and retaining information inside their minds. So while we simply cannot claim that animals do think, see, sound out, words in their mind …it is safe to assume they are able to create and retain unspoken language in their minds.
This is the most simple outline of an answer I can give considering all the factors. As I said earlier, “language” or communication varies from species to species: CFor example, in highly intelligent, socially developed animals like elephants, we see that the language center in their brain evolved similarly to our own—that is, it is extremely large. Which means they are, to a certain extent, using it for similar purposes as humans. And we see that like us they are able to get across very complex forms of information to one another—organizing and executing multi-step plans in large groups, expressing deep emotions, passing along detailed family history…Yet we still have very little understanding of how they are actually communicating!
Dolphin language, on the other hand, we have a bit more grasp on. We know they have grammatical structures similar to our own, as well as entirely seperate forms of physical communication not paralleled in human behavior (such as “bubbles”)
And then there are whales, with mysterious distant whale-songs. Bats who “argue” via eco-location. Insects that hum rhymes to one another or “chat” about and memorize the stars. Dogs that understand human commands better than a 3 year old human, …and better than the howls/tones of their own species!
…Let’s not even get into chimpanzees that are trained to use American Sign Language! 😉
On top of that, humans need language in a much more vital way than other animals. We rely on it. It’s what sets us apart. So the way we perceive words, and think words in our heads, and have private thoughts, are all very specific traits to our very weird species.
Last, there are theories that animals “think in pictures” rather than in structured language. Comparisons have been drawn between the way people with Aspergers Syndrome and Autism “see words” or images. But again, this doesn’t negate thinking in language. It just negates thinking in words as we know them.
In other words (hehe, pun intended), you’ve opened up a whole can of worms with a very simple, yet important, question! There’s no exact, or necessarily true, answer. There are a lot of amazing theories that (in my opinion) suggest animal language simply can’t be compared to human language, and therefore can’t be understood in human terms. Still, we do know they use language for many of the same reasons we use it. And I think it can be safely said that they must being “thinking” in that language, too.
Hope this wasn’t more confusing than it was informative! 🙂