Answer by Michael Wilson, Student of Linguistics at UT Austin
Let's try an experiment to find out!* I'll show you a few objects, and give you some sentences with them. Now, unlike a normal situation, these will be written, not said, but you'll have to bear with it. (No peeking ahead to the end or the experiment won't work!)
Condition 1: NounsHere's a set of strange objects:
Here's the first pair of objects:
Well, that wasn't so bad, was it? Make sure you've read through all the text with each pair of objects before you answer the question after the next picture!
You'll note that we used a noun in this case: a blick. One things nouns tend to do is refer to objects, which have some convenient properties. For one thing, objects tend to maintain their visual appearance. If you leave the room and come back, the blick will probably won't change much. You can move the blick around (if you made one), and it will look the same in different contexts, for the most part.
It's important to note that nouns don't always refer to things that have these properties. Nouns can also refer to abstract things, like progression, call (as in a phone call), comfort, and zeal. But the prototypical function of nouns, their most common uses, is to refer to a kind of object that looks roughly the same across situations. If somebody asks you for a typical noun, you're more likely to come up with ball or dog than ennui or even love, no matter how wistful you may be.
Just a forewarning: we're going to focus a lot on strategies kids can use when learning words for the rest of this answer, since they have a harder job than adults. They don't have the advantages of knowing what nouns and verbs are already: they've got to figure it out! But kids can use several strategies for learning nouns: they can learn that a noun's prototypical function is referring to an object; they can observe a correlation between the presence of a word in different situations and a particular object in the same situations; and they can (unconsciously, most likely) draw inferences that nouns most often refer to a whole objects, since these stay together when they move and when you see them in different places. Now, let's look at verbs.
I'm going to give you a considerable head-start in the second half of our experiment: I'm going to assume that you are able to figure out the syntactic differences that tell you whether something is a noun or a verb, which is itself a considerable feat. I'm also going to assume that you know verbs typically refer to actions or events. This is a huge leg up from the situation with nouns, where I justified how kids learned that nouns refer to objects since objects tend to stay together when moved and look the same in different contexts.
Here's our test with verbs. We've got some actions in the following pictures, and I'm going to make up some verbs for them. Once again, all corresponding verbs will be given after the picture, in alphabetical order. It should be easier; after all, you've got four pictures to keep track of instead of six, and I've given you a head-start in knowing the kinds of things verbs refer to and how to pick them out of a sentence.
Condition 2: VerbsHere's our full set:
And here's the first of the pairs, which were so useful last time:
Now, we're back to our original group:
Wait a second, that wasn't harder than the first case! What's going on?! Well, let me ask a more pointed question: is this keeting?
In reality, any of our four pictures can be described to children and adults both, in a very natural way, as keeting, because it's just my way of saying going: "The man on the bike is going fast," "The dog is going to the dog party," "Daddy's going on a trip, see?," "The runner is going around the track." And this isn't some strangely defined technically used verb that has some weird criteria governing its use: it's a verb we use every day. It's one of the first verbs kids learn, probably not because it's easy to understand, but because it's so widely used. We feel comfortable using it; we know when we can describe something as going and when we can't, even when more specific descriptions, like biking, flying, driving and running are available if we want. And think about other unremarkable, everyday verbs like this: what's so obvious about picking something up that we use it to express anything from physical contact from above causing vertical motion off a surface to collecting a package addressed to you, not to mention uses like I'm going to pick up some milk at the store? Verbs have also got to take on the job of encoding information about when something happened, and whether it's finished or ongoing (tense and aspect), which I've even conveniently ignored in our little test. How can we figure out what they mean, when each picture and situation is clearly very different? How do we extract the commonalities between them?
It takes time. It takes practice.
To put this into hard numbers, if kids know one word, it's probably a noun. If they know five, a noun's usually one, and verbs don't even usually show up. When they know around fifty words, somewhere in the range of 20-25 are nouns, and a paltry two or three are verbs. You have to see and experience many more situations before you know what going really means than you do to know what a blick is.
What else is going on?Think once again about what nouns refer to: objects, which are relatively permanent, shape-maintaining things that look the same in different contexts. You can identify an object you don't know the name of if you see it in a new place pretty easily, but you can't tell if an action is the same as another unless you hear someone classify it as such. You can find similarities, sure, but you can't be sure if the word you use will be the same: after all, depending on where the speaker is and the context, the same situation could either be described as coming or going or both! It's not even consistent across languages. In English, if someone knocks at the door and you want to tell them that you're on your way to answer, what would you say? Probably, like most English speakers, you'd stick with a typical "I'm coming!" But Spanish speakers would instead say, "¡Voy!" (I'm going!). The reason for the difference is that in English we're taking the perspective of the knocker when answering, whereas Spanish speakers maintain their own. In both cases we're referring to the exact same event, but how we talk about it has to do with whether we we're conceptualizing the motion as closing in on the destination (coming) or as setting out from the starting line (going). There's nothing about the actual event that makes us choose one verb over another to describe it; it all depends on how you look at it. Think of the poor kids who have to figure out all the complicated mental gymnastics involved in the perspective displacement required just to tell someone something as basic as the fact that you're on your way there!
Verbs are tough because they inherently refer to abstract things about the motion in question--what's important about it, so to speak--which you can't learn as easily from direct experience, since it greatly depends on what a speaker's attitude toward the action is. But we're still not done yet: there are even more complicating factors we've got to consider.
Let's try one more test: which two of the three situations below would you use the same verb to describe?
But they've also found that if you're a Spanish speaker, you'd tend to answer differently: you'd probably choose the first and the third situations: "El hombre sube la escalera rápidamente" (The man ascends the stairs quickly), and "El hombre sube la escalera lentamente" (The man ascends the stairs slowly). This represents a difference in the prototypical function of verbs in each language: in English, verbs tend to encode the manner of the motion first and foremost; and in Spanish, verbs tend to encode the direction of the motion first and foremost. This isn't an absolute, of course; English does have verbs like ascend after all. But they're used so sparingly compared to manner verbs, and vice versa for Spanish, which uses manner verbs much more sparingly than direction verbs. So English speakers tend to focus on the way someone moves as most relevant to verb meaning, whereas Spanish speakers tend to focus on where they're going.
To add yet another brief example of the variety of functions verbs perform, verbs in Korean are used to refer to things that we in English would use adjectives, an entirely separate part of speech, to indicate; and when Koreans do use adjectives, they're usually derived from a verb. It'd be as if we said, "The ball is redding" just like we say, "The prisoner is escaping."
So, go over that for me one more time...Now, let's to go back to children: they have to sort out this entire tangled mess. Unlike nouns, which refer to the same kinds of things in English and Spanish (and in general across languages), verbs refer to a whole action in a particular context, but only some key features of the action are relevant when extending its use to other contexts. These key features are what the real meaning of the verb is: an abstract je ne sais quoi that determines what we're really focusing on and encoding about a motion or event when we use a verb.
To sum up the verb situation: verbs aren't as clear in meaning as nouns: they can refer to very generalized things about an action that depend not only on abstract features (direction or manner), but also the participants' and speakers' perspectives on the event (coming vs. going, looking vs. seeing, hearing vs. listening, knowing vs. understanding), and they are used more often in more generalized ways than nouns. (This last one may sound unclear, but consider that a mom is more likely to use go, a general verb, with her child, than object, a general noun, to describe things. Compare how natural it would sound to say to a kid, Look at them going over there! to Look at all the objects! The second, to me at least, sounds a bit strange, like a robot mom.)
Nouns, once again, typically refer to relatively permanent things, that look mostly the same over time and in different situations, and their meanings don't tend to vary as much as the meanings of verbs across different languages.
All this leads us to a general conclusion:
Basically, children (and people in general) learn nouns more easily, because verbs are hard.
*This experiment was adapted from Smith, L., & Yu, C. (2008, March).. Cognition, 106(3), 1558-1568. doi:10.1016.
Caselli, M. C., Bates, E., Casadio, P., Fenson, J., Fenson, L., Sanderl, L., & Weir, J. (1995). A cross-linguistic study of early lexical development. Cognitive Development, 10(2), 159-199.
Papafragou, A., Massey, C., & Gleitman, L. (2002). Shake, rattle, 'n' roll: the representation of motion in language and cognition. Cognition, 84, 189-219.
Smith, L., & Yu, C. (2008, March).. Cognition, 106(3), 1558-1568. doi:10.1016.
(Pictures were grabbed randomly from whatever looked good in a Google image search; and, in some cases, the articles above.)
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