You may have heard that dogs and cats only see in black and white. That’s wrong; these animals are dichromatic, which means they have limited color vision. What is true, however, is that their vision is different from ours. Other animals, such as some bats and rodents, are indeed monochromatic: they only see in black and white and shades of grey.

Before you start feeling smug, consider the limitations of your own sensory system. Some other animals, such as boa constrictors, can see infrared light, which is invisible to you and me. And you know about dogs’ sense of smell, which is much more refined than ours.

The point is that we don’t perceive the world as it is, we perceive it as our senses allow us to see it. Our sensory system presents to us an abstracted view of reality. (This suits me fine; our sensory system has evolved to allow creatures like ourselves to survive and thrive in environments like ours.) And on top of this already abstracted view, we layer another abstraction: language.

I have a dog. When your eyes read the word “dog” in the previous sentence, your nervous system started conjuring images and concepts. At this point, you probably even have an idea of what kind of dog I have, even though I haven’t shared that information with you. Is it a big dog? Is it male or female? Does it have long or short hair? What color is it? How old is s/he? Does s/he have any physical infirmities or other peculiar characteristics?

You can’t know at this point. This word “dog” leaves a lot out by necessity; we wouldn’t be able to communicate effectively​ if we had to delve into particularities all the time. I could’ve used a more specific term, such as “mutt” or “bitch,” to describe my dog. That would’ve given you more information, but these terms have connotations that would’ve derailed my argument. “Dog” is a useful level of abstraction for the purpose of our discussion.

“Dog” and “mutt” describe the same sort of thing but do so at different levels of abstraction. In his book Language In Thought and Action, S.I. Hayakawa uses the image of a ladder to describe these types of relationships. Very abstract concepts are at the top of the ladder, and very concrete particulars are at the bottom. There can be many rungs in-between.

We move up and down this ladder of abstraction all the time in our day-to-day communications. For example, imagine that I want to show you a photograph representing this concept:

I can’t do it. It’s impossible for me to show you a photograph of a musician; by necessity, I must show you something more specific than that. I must step down one rung on the ladder of abstraction:

Actually, that won’t do either; I need to get even more specific than that. The photo must render something captured in the “real” world, so by necessity it’ll have to look something like this:

Image by By Carl Lender CC BY 2.0, via Wikimedia Commons

In other words:

At this point, I must be careful about the image I choose. If you know who Jerry Garcia is, I run the risk of derailing your train of thought: now I’m no longer evoking just the concept of “musician,” but a whole other lot of things too.

We can also get more abstract, going way up the ladder:

Eventually, the concept of “musician” gets abstracted out of the conversation entirely. At that point, we’re no longer talking about music.

Getting the level of abstraction just right is essential if we are to set the right context and communicate effectively. I find this image of a ladder useful when I’m thinking about the terms to use when creating distinctions and labels in information environments. Consciously choosing to move up or down the ladder can make a big difference when making information more findable and understandable.