There is a bit on the wikipedia page about the pathetic fallacy which might help.

In science, the term "pathetic fallacy" is used in a pejorative way in order to discourage the kind of figurative speech in descriptions that might not be strictly accurate and clear, and that might communicate a false impression of a natural phenomenon. An example is the metaphorical phrase "Nature abhors a vacuum", which contains the suggestion that nature is capable of abhorring something. There are more accurate and scientific ways to describe nature and vacuums.

Another example of a pathetic fallacy is the expression, "Air hates to be crowded, and, when compressed, it will try to escape to an area of lower pressure." It is not accurate to suggest that air "hates" anything or "tries" to do anything. One way to express the ideas that underlie that phrase in a more scientific manner can be found and described in the kinetic theory of gases: effusion or movement towards lower pressure occurs because unobstructed gas molecules will become more evenly distributed between high- and low-pressure zones, by a flow from the former to the latter.[13][14][15] — wikipedia: pathetic fallacy: science

Literal readers might get hung up on the a kind of language which might be considered overtly figurative (full of metaphor and simile) if the particular expressions aren't so widely accepted. These two examples in wikipedia could be cases of anthropomorphism if only humans can "abhor" or "hate" something.

Yes, yes, and yes...

I quite readily anthropomorphize dogs. I am quite aware that even a very bright dog has limits which prevent them from having the sort of complex, abstract ideas that humans have. On the other hand, most dogs seem abundantly capable of having wants, fears, preferences, learned behaviors, memories of good and bad, and various instinctive drives that add up to fairly complicated behavior.

A man and a dog connect at various levels, mutually, which is a pleasurable experience (usually -- unless the dog is trying to get you to play by shoving its slimy tennis ball into your mouth). Were I to treat the dog as a warm, wetware mechanism, there would be very little pleasure in interacting. Indeed, it might even be desirable from an ecological point of view to embrace our connection with all living creatures. Better that than treating ones cow like a machine, the forest like a warehouse, the birds like ornaments.

Anthropomorphizing one's car, one's computer, or one's force of robots is common, but mistaken. A geranium has more personality than a robotic vacuum. My computer knows nothing, feels nothing, and most of the time, does nothing.

I think anthropomorphism is a two way process.

For example making a close comparison between humans and chimps can end up devaluing human attributes by spreading them to thinly and exaggerating human animal similarities (i.e. mischaracterizing human attributes).

Some people give animals or machines human attributes in order to try and demystify or deflate them in humans. Or to see where an attribute might have arisen in a simpler form.

So the problem could be said to be mistaken or politicized or ideological comparison.

I quite readily anthropomorphize dogs. I am quite aware that even a very bright dog has limits which prevent them from having the sort of complex, abstract ideas that humans have. On the other hand, most dogs seem abundantly capable of having wants, fears, preferences, learned behaviors, memories of good and bad, and various instinctive drives that add up to fairly complicated behavior.

A man and a dog connect at various levels, mutually, which is a pleasurable experience (usually -- unless the dog is trying to get you to play by shoving its slimy tennis ball into your mouth). Were I to treat the dog as a warm, wetware mechanism, there would be very little pleasure in interacting. Indeed, it might even be desirable from an ecological point of view to embrace our connection with all living creatures. Better that than treating ones cow like a machine, the forest like a warehouse, the birds like ornaments.

Anthropomorphizing one's car, one's computer, or one's force of robots is common, but mistaken. A geranium has more personality than a robotic vacuum. My computer knows nothing, feels nothing, and most of the time, does nothing. — Bitter Crank

As always Bitter, you've garnered an increase in my respect for you, not to mention the sheer amount of appreciation. I would readily agree with the benefits you've mentioned above. I mean, you've done a fantastic job of tempering my own approach here. Thank you for that.

So, not all anthropomorphism is something to be avoided. It's not 'bad' in and of itself.

That being said...

When we're looking to acquire knowledge of what humans and animals both have in common as far as the content of their respective thought and belief systems, it ought be avoided.

...Some people give animals or machines human attributes in order to try and demystify or deflate them in humans. Or to see where an attribute might have arisen in a simpler form.

So the problem could be said to be mistaken or politicized or ideological comparison. — Andrew4Handel

Maybe. Attributing particulars that are exclusive to humans to that which has none is anthropomorphism. One cannot see if these particulars are capable of arising in a simpler form solely by attributing them.

The OP begins discussion that underwrites all that...

I actually try to avoid anthropomorphizing; animals have their own raisons d'être; they don't need ours, and we quite often infantilize animals as well as anthropomorphize them. So we really ought, and we really can, make connections with other creatures as other, and not an extension of our beings.

https://en.wikipedia.org/wiki/Anthropomorphism

The Wikipedia entry is good. Apparently anthropomorphism is considered an innate tendency starting from childhood.
I don't feel I have ever been one for anthropomorphizing though. I also find it difficult to guess what other people might be thinking and I try to be cautious about making assumptions.

Everyone's mental states might be very different. It is actually hard to compare any mental states because of their private nature. I think that similar behavior may or may not entail similar mental states but I would not rush to conclusions.

I have often wondered what makes us believe a person or creature is conscious. We believe other entities than us have conscious states without a causal theory and we seem to judge something to be conscious on subtle clues. I have used the example in the past of a woman flicking her hair. That kind of little gesture seems to imply consciousness whereas a sophisticated response by a computer doesn't'.

The problem with machine human analogies is is that machines do things differently than humans even if the same or better results are produced. But some "trivial" behaviors seem implausible without consciousness.

People treat pets like family which is understandable. But they don't have the same expectations of them. They pander to them and don't make them earn a living.

The problem is when you try and give all animals the same status and rights as pets or humans it becomes an impossible utilitarian calculation and burden.

So utilitarianism has been seen as more problematic when you apply it to other entities because it ends up diluting the type of average pleasure you are trying to attain. Can a pig appreciate Socrates?

we don't make them earn a living. — Andrew4Handel

We tried to make our dog contribute to household income, but she was unwilling to get to work on time, pay attention to direction, observe break times, and so forth. Actually she was quite successful as a greeter at Walmart, when she was on the job. Retrievers are kind of made for that sort of work. But then she would wander off, sniffing around the meat coolers, stealing pot roasts and eating them raw right on the floor... People objected.

We found it was easier to just let her spend the day sprawled all over the couch (except when she was rushing into the kitchen whenever she heard certain sounds connected with food she liked--crinkly plastic, the apple peeler, the can opener...). She was a good exercise enforcer. She didn't like it when she was denied a 90 minute walk.

Anthropomorphizing one's car, one's computer, or one's force of robots is common, but mistaken. — Bitter Crank

You make it sound as if these folks are actually mistaking their car, computer or robots for actual anthropoid-like beings in the moment. I guess when you are watching a film about human-like light shadows you're also mistaken and that folks usually aren't aware that they are.

Perhaps we anthropomorphize other humans, which are really just soulless meat robots.

these folks are actually mistaking their car — Nils Loc

I hope they are not actually mistaking their car for a person. If they are, they need to see a neurologist on the double (see The Man Who Mistook a Hat for His Wife, by Oliver Sacks, neurologist).

I've met a few soulless meat robots.

No "The mistake" is supposing that a machine -- like a computer -- can be a person, can be an intelligent, aware, being. This is still mostly a projection into the future. Otherwise, getting overly attached to one's car, one's bicycle, or roller skates is just setting one's self up for disappoint when the car gets dented, the bicycle gets run over (without the rider being on it, one hopes) or one skate gets mysteriously lost.

Everyone's mental states might be very different. It is actually hard to compare any mental states because of their private nature. I think that similar behavior may or may not entail similar mental states but I would not rush to conclusions. — Andrew4Handel

Yes. It is best to exercise caution about mental states when the only measure of evidence is behavioural observation.

It is hard to compare mental states because of a whole plethora of reasons. However, it is not so hard to acquire a good understanding of them. Langauge shows that mental states aren't so private after all. We can use what we learn through language to acquire knowledge of that which exists in it's entirety prior to our account of it.

So...

How do we know which things are exclusive to humans and which things are not? If we do not know that much, how can we possibly know when anthropomorphism is happening?

How do we know which things are exclusive to humans and which things are not? — creativesoul

I can think of lots of things that exclusive to humans although some of these involve artifacts.

I would say words, writing and drawing are exclusive to humans and probably language

(Language ,because I would class animal interactions as communication as opposed to a fully fledged language with concepts, sophisticated representations, grammar and thousands of words)

Playing musical instruments. Doing Philosophy. Schadenfreude. Storytelling. Concepts. serious technology and invention. Economics. Fantasy. Religion.

Driving a vehicle. Space exploration. Culture. Laughter. Crime.

Documenting History. Science. Symbolism (To the great extent it is found in humans) Reflection on death.

I think some of the differences can't be verbalized they are just apparent on observing humans and animals.

Partly to do with intelligence and communication skills.