Seems pretty straightforward, right?

There's a martian, it has a telescope, and Ingrid is seeing it.

"But wait!" about half of you are saying right now,

"that’s not at all what I thought it meant."

"I thought it meant that Ingrid had the telescope and she’s using it to look at the martian."

Well, you’re not wrong either.

This sentence is ambiguous.

In one meaning martian has the telescope, in the other meaning Ingrid has it.

So how is it that one sentence can have two different meanings?

Well, the difference between the two meanings is who has the telescope.

In other words, which part of the sentence "with a telescope" is modifying.

Under one meaning, "with a telescope" is modifying "the martian."

In this case, we don’t know anything about the seeing.

Under the other meaning Ingrid has the telescope and now "with a telescope" is modifying "saw".

How did Ingrid see the martian? With a telescope.

Which martian did she see? We haven’t said anything about this.

Arrows like this are great, but they're kinda imprecise.

Is the arrow pointing to "the"? Is it pointing to "martian"? Is it pointing to both of them?

With just an arrow we don’t really know.

Instead we use what linguists call a tree structure diagram.

You might recognize it from this video.

Let’s start with a basic example.

Here’s our sentence. What can we figure out about it?

One thing you might notice is that if we swap

"Ingrid" and "the martian" we get a different sentence,

but it’s still perfectly good.

That wouldn’t be the case if we swapped "Ingrid" and "saw",

and it wouldn’t even be true if we swapped "Ingrid" and "martian", leaving "the" behind.

So there’s something really special about "Ingrid" and "the martian".

They’re sort of the same thing.

We call them NPs for noun phrases.

They both have nouns in them,

but they can also have other things like the determiner "the".

If we’re talking about NPs then what about the verb?

Just like the noun has a noun phrase the verb has a verb phrase.

And we also have an "S" that stands for sentence.

Now what do we do with the "with a telescope" part?

Since "with" is a preposition we’ll call it a Prepositional Phrase.

And since I’m not worried about the internal phrase structure of the PP,

I’m going to use this triangle to indicate the whole phrase at once.

Let’s start with what happens if the martian has the telescope.

Since the whole thing "the martian with a telescope" is what Ingrid saw,

"with a telescope" has to be part of the martian's noun phrase.

Now what happens if the telescope is associated with seeing?

Who did Ingrid see? the martian.

How did Ingrid see? with a telescope.

Now the prepositional phrase is up here.

You can read the linear order of the sentence off the tree by reading along the bottom.

"Ingrid saw the martian with a telescope."

But notice when we do this, it doesn’t matter where the prepositional phrase attaches.

Whether it’s up here at the VP level or down here with the NP,

it’s still going to give us the linear order that puts the prepositional phrase

right at the very end.

Linguists call this phenomenon attachment ambiguity,

since the confusion arises from the fact that the linear order isn't giving the listener

clear information about where the PP attaches.

So what? Is this just a weird property of sentences with the word "telescope" in them?

Probably not.

Let’s try it with a whole nother set of words.

What about the sentence "I wrote the letters on the kitchen table."?

This sentence is also ambiguous.

Under one reading the letters are currently on the kitchen table and I wrote them.

Under the other reading "the kitchen table" goes up here with the VP.

And in this configuration the letters were written at the kitchen table,

but they could be anywhere right now.

Here are some more sentences that are ambiguous. You should think about them!

"Edna hit a yeti with a frying pan."

"I bought this unicycle for my best friend"

"Nigel remembered the concert after the rainstorm"

It’s good practice to sit down and think about the different possible readings that

each linear order could have.

Bonus!

Here are two more ambiguous phrases that have slightly different attachment ambiguity.

"I will eat the pie that you will bake tomorrow."

"One-eyed, one-horned, flying purple people eater"