8.12 Psycholinguistics: Traces in the Mind

We’ve claimed that when the operation MOVE moves a head or a phrase into a new Surface Structure position, it leaves a silent copy of itself (a trace) behind in the Deep Structure position. This unit presents psycholinguistic evidence that these traces do form part of our mental representation of sentences.

Check Yourself

1. Which of the following illustrates the position of the trace in the wh-question What did Christina order at Chipotle?

  • What did Christina order at Chipotle what.
  • What did Christina order what at Chipotle.

2. Which of the following ungrammatical sentences gives evidence that unpronounced traces exist in our mental representations of sentences?

  • *Did you ate what for lunch?
  • *What did you eat sandwiches for lunch?

3. Predict which sentence would lead to more eye movements to a picture of a rabbit after the verb chase:

  • What did the fox chase ^ into the hedge?
  • Did the fox chase ^ the rabbit into the hedge?

Video Script

We’ve been working with a theory that says that the operation MERGE generates a Deep Structure. For this wh-question, Who did Lucy invite to wedding, the Deep Structure looks like this. This wh-pronoun who refers to whoever it is that Lucy invited, and it is generated in this position in the complement of the Verb head, which is exactly where the noun phrase complement would be if we know who it was that Lucy invited. The preposition phrase gives us more information about the event of inviting, and it’s adjoined at the V-bar level. Because this is a wh-question, there’s both a [+Q] feature and a wh-feature in the C-head position.

Then the operation MOVE does its work.The wh-phrase moves up to the Specifier of CP, where it can support the wh-feature in C. Then do comes into the T-head in its past-tense form, did, then moves up to the C-head position.

One element of this theory that we’ve been taking for granted so far has to do with the trace that’s left behind when something moves. When we speak a sentence, we pronounce words in their Surface Structure positions, but we don’t pronounce anything in the Deep Structure position. But when we draw the tree, we show the deleted copy in that Deep Structure position, to suggest that, in the underlying representation, in our mental grammar, there’s something unspoken occupying that position.

There is some linguistic evidence for the existence of traces in our mental grammar. We’re claiming that there’s a trace in this position in the complement of invite. Notice that it’s not possible for any other phrase to occupy that position: if we try to put another noun phrase in the complement position, we can observe that each attempt is ungrammatical.

There’s also some psycholinguistic evidence for the existence of traces. The evidence comes from what’s called a visual world experiment. In this kind of experiment, a person’s eye-movements are measured using a device called an eye-tracker. The eye-tracker records where their eyes move while they listen to a spoken paragraph and look at a visual scene. The spoken paragraph goes like this:

This story is about a boy and a girl. One day they were at school. The girl was pretty, so the boy kissed the girl. They were both embarrassed after the kiss.

The idea behind a visual world experiment is that you look at what’s being mentioned. So when you hear the boy, your eyes move to the picture of the boy, and when you hear the girl, your eyes move to the picture of a girl.

At the end of this paragraph, one group of listeners heard a wh-question, Who did the boy kiss that day at school? A different group of listeners heard the same paragraph, but followed by a yes-no question, Did the boy kiss the girl that day at school?

These two sentences are similar in their structure, but they have a crucial difference. In the complement of the verb position, the yes-no question has an overt noun phrase, the girl. In that same position of the wh-question, there’s a trace, a deleted, unpronounced copy of the moved wh-word.

The researchers focused on this exact position in the spoken question: they observed where the participants’ eyes moved after the verb kiss. They compared how often the participants looked at the girl vs. how often they looked at the boy. In the yes-no question, when they heard the verb kiss, people looked at the boy 11% more often than to the girl, maybe because the boy is the one doing the kissing. But in the wh-question, when they heard the verb kiss, people looked to the girl 21% more than to the boy.

In both scenarios, the boy kissed the girl. But people’s eye movements differed in the two conditions. We know from previous studies that eye movements are quite closely synchronized to what’s being mentioned in the discourse. In this study, people’s eyes move to the girl not just when the sentence refers to her overtly, but also when the deep structure contains a trace that refers to her. The evidence from this eye-tracking experiment suggests that traces don’t just exist in tree diagrams, but also in our minds.

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8.12 Psycholinguistics: Traces in the Mind by Catherine Anderson is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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