One of My strongest memories is watching a documentary where they claimed dogs don't dream, and my dogs directly in front of the TV making little sleep barks and moving legs deep into some dream.
Let's be honest we are animals and the rest aren't all that far behind us.
Not sure about thoughts, but cats are interesting in their level of committment to their intent when they "decide" they want to do something. They are laser-focused and its hard to actually meaningfully distract them from the execution once the order's been placed haha.
Watch them sometime. Cat.exe are very deiberate little critters. It reminds me of when you hit the share sheet on iOS but you change your mind and try desperately to navigate away from it popping up or hoping you can cancel out the instruction but nope. Its coming
That said, plenty of humans do not have a voiced internal experience. The lack of language does not imply a lack of cognition. I would expect that the brain of a closely related organism, say a chimp, would have many similar experiences generated by the same stimuli. Would they experience green like I experience green? I can't even say that about a person sitting next to me, but they probably have an equivalent experience.
That said, if we had a way of communicating could we reach agreed terms? I can do that with my cat, so I would think he has an understanding of me and my behaviours along with what tends to happen when I do certain things like clap then shake my hands at the end of a treat session. He knows there are no more treats, he associates that with my hands clapping and shaking, so we communicate. Does he have a voice in his head describing it? Probably not. Does he have Meows? Again, probably not, but he would have a sense and memories of previous times.
Probably not expressed as a voice, but definitely thinking.
One of our cats would regularly get "that look" on her face and we'd tell her "Lorelei! Stop thinking evil thoughts!" then she'd go on a tear. Clearly plotting what she was going to do.
I think that it's on a sliding scale. Some animals clearly have some kind of inner thought process, and clearly have their own personalities. Others not as much. I know that with cats, for instance, there are tools you can use that allow cats to communicate certain concepts to people, stings of buttons that are each linked to a discrete word. Cats can learn to string button presses together to 'say' things to their keepers. (Apparently the most common thing they ask for is clean water, so clean your cat's water daily.) That may not be evidence of "thought" in the way that you're thinking about it, but there's clearly some form of cognition going on there.
I think so. I have parrots who are at a 4 year old human's intelligence level. They do things they know they shouldn't and wait for me to turn my back, it's like they know they shouldn't but have an intrusive thought and act on it. Of course, once I say "excuse me..." With the dad tone, they fly to their cages and pretend they did nothing. To me that takes thought and reasoning, desire, planning, action, etc. On their part.
So many people making stuff up they have no way of actually knowing in this comment section. No wonder religion is so widespread!
The true answer, unsatisfying as it may be, is that we have no way of knowing the subjective internal experience (often referred to as 'consciousness') of other humans, let alone other animals. For all we can know, a rock could have thoughts. We really, for now at least, can't know. Unfortunately.
I'm sure it depends on the animal. In fact humans think in at least two inner voices.
The ear consciousness is receptive, and the speech consciousness is active.
What I mean by this is a dog or another animal that spends a lot of time with people likely has a passive inner voice of their owner. A dog might hear an owner yell no when they go to do something the owner doesn't like, even if their owner isn't around.
Animals that are capable of speech such as a parrot, will likely have an active speech consciousness. Which is more somatic in tone.
For example, when I am in active speech consciousness I can feel my jaw and tongue muscles move. When in passive listening consciousness, my ears might move or strain to try to hear the inner speech.
With practice these somatic sensations can be decoupled from their internal sense consciousnesses. Which tends to help them quiet down and deepen meditation.
This is one of my favorite practices that's accessible for people who don't really meditate. The guided meditation is the first fifteen minutes of the video, so you don't have to listen for the whole hour to get an inkling of what I'm pointing at.
They are like people who never learn language. This sometimes happens to deaf people who are not taught to use sign language. Any inference about such a person’s intellect and capacities should be abstracted towards mammals at least.
I'm not sure about all animals, but I'm pretty sure my sphinx cat does. I have to give her medicine every day and not only does she knows when it's time to get it, but there are times where she will hide under the bed. Just laying down and looking at her and asking her to come out is enough to get her to wander over slowly and get it. It's funny, you can almost see the thoughts going through her head as she realizes she has to just give in and go get her pill.
No, at least not most animals. There was a study a while back that showed that animals think by reducing the world to a series of binary choice that they react to in the moment. I imagine it's a lot like when you're playing a sport or video game and things get very intense and fast paced; your inner monologue isn't telling you what your next move will be every second, you're just reacting on instinct. That's probably how animals see the world all the time.
That being said, "animals," is a broad category, and some of them may be capable of creating an abstract narrative for themselves. It was recently discovered that whale songs have a phonetic alphabet, which means their language may be as complex as ours. If that's the case, they may be capable of using that language to build an internal monologue.
How do you know other humans have thoughts? There is no way of measuring it, and there is no way to tell if someone is lying about it. You could measure brain activity. But There is no need for brain activity to be accompanied by experience. There is no law of nature that says that electrical signals are accompanied by experience or thoughts. There is also no way to tell the difference between a millimeter cube of brain from any animal. So if you believe that brain activity is represented by thoughts, then there is absolutely no way to draw an arbitrary line between humans and animals.
None of them have language beyond associating a small number of specific sounds or words to objects or events but I would bet my legs just above the knee down that Dolphins monologue "Squee-aww" when they spot a scuba diver. Dogs definitely daydream about you calling their name when you're away for a long time. If they couldn't in some way internalize the call then they would not remember it.
EDIT: To add onto my claim that they don't have language beyond a certain level, that's what we've been able to prove so far. We know that some of the smarter animals, such as dolphins, crows, and gorillas can understand quite a few words with daily training and even use and pass down taught language to limited capacity, but the longest experiments for complex languages with these animals have all resulted in "failure" to teach them or learn from them to the extent of being able to have conversations or form complex statements.