An EEG investigation of the role of prediction and individual differences in word-pair semantic priming

Xiao Yang

Graduate Research Competition

March 29, 2016

The role of predictionGeneral question:

• Do speakers make predictions about upcoming speech content? If so, what makes one a better predictor?

Linguistic phenomenon of our interest:

• Word-pair semantic priming

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Word-pair semantic priming

• After encountering a prime, it is easier to activate a semantically related target, than an unrelated one.

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(prime) (target)

CAP hat

KEY hat

Related

Unrelated

Using EEG to study priming effectsEEG (electroencephalogram)

• records real-time voltage fluctuations in the brain

• captures the brain activities triggered by a particular linguistic event (e.g. encountering a related or unrelated word)

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EEG component of interest: N400

• N400: A negative-going wave peaking at 300-500ms

• N400 priming effect: Related word pair elicits N400 reduction in amplitude (Lau et al., 2013)

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CAP hat

KEY hat

unrelated

related

(Negative plotted up ↑)

Mechanism of N400 priming effectWhat’s the priming due to?

Possible mechanism 1:

• The activation of the prime word passively spreads to semantically related words in the mental dictionary.

• If so, then the N400 priming effect is based solely on the semantic relatedness between the prime and the target.

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Mechanism of N400 priming effectPossible mechanism 2:

• The priming is in part due to an active process of prediction; the comprehender can actively generate an expectation for specific words that are semantically related to appear.

• If so, then the N400 priming effect can be conditioned by some external cues that influence the comprehender’s expectation about whether the word pair will be semantically related or not.

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CAP

HAT

KEY

Mechanism 1: Passive association between mental lexicon

CAP

HAT

KEY

cap

CAP

HAT

KEY

cap

CAP

HAT

KEY

cap

CAP

HAT

KEY

Mechanism 2: Active prediction

CAP

HAT

KEY

cap

CAP

HAT

KEY

cap

CAP

HAT

KEY

cap

Since “cap” just appeared, I bet

“hat” will appear soon

Relatedness cue• Relatedness cue has been shown to modulate reaction time in

behavioral studies on word-pair priming (Hutchison (2007))

• For a given trial, a relatedness cue is presented before the word pair, indicating how likely it is to encounter a related word pair (proportional cue reflects real proportions)

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80% Related CAP hat

Cue (1000ms) Prime (500ms) Target (900ms)

hat20% Related KEY

Experiment design: Conditions

• 160 prime-target word pairs

• 280 filler pairs, used to establish relatedness proportion

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Related Condition Unrelated Condition

Relatedness Cue Prime Target Prime Target

80% Related CAP hat KEY hat

20% Related CAP hat KEY hat

Experiment design: offline measure• Does each participant exhibit the same level of

sensitivity to the cue manipulation?

• Previous study on older adults has shown that actively generating predictions could involve similar mechanisms to verbal abilities (DeLong et al. (2012))

• Therefore individual participant’s sensitivity to the cue could be related to their personal verbal fluency

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Experiment design: offline measure• Individual variation in verbal fluency can be measured

by an offline ‘letter and category’ task, as an index of each participant’s verbal fluency (Spreen & Strauss (1998))

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Within 1 minute, tell me all the words for office supplies that you can think of.

Paper,Stapler,Eraser,Sticky note,Pen,…

Experiment procedure

• Participants: 22 KU undergraduate students (all native English speakers)

• Procedure: Offline measures (verbal fluency, attentional control, and working

memory)

EEG recording while the stimuli are visually presented

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Research questions

1. What’s the effect of Relatedness on N400 amplitude? Related pairs will lead to N400 reduction

2. Would participants actively make prediction using the relatedness cue?

If so, ’80% related’ will likely lead to greater N400 reduction (as suggested by Lau et al. (2013)’s results)

3. Will an individual’s verbal fluency have an effect on whether they show predictive effects?

If verbal fluency correlates with sensitivity to the relatedness cue, then it suggests some relation between verbal fluency and their sensitivity to the cue manipulation

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Results• The main effect of Relatedness

Related word pairs elicited N400 reduction compared to unrelated pairs

• The effect of Relatedness Cue Marginally significant between 80% and 20% cue

22All participants, 80% Related All participants, 20% Related

Results• Participants with high verbal fluency shows bigger N400

priming effect than low verbal fluency participants, when the cue is ’80% related’. The priming is in part due to actively generating predictions by using

the cue (for high verbal fluency participants)

23Low VF participants, 80% related High VF participants, 80% related

Conclusion• Word-pair semantic priming involves actively generating

predictions about the upcoming word

• Individuals with higher verbal fluency were more sensitive to the relatedness cue Verbal fluency is an individual difference that modulates

comprehender’s ability to make use of the cue and generate lexical predictions

Consistent with previous N400 priming studies using verbal fluency measures among older population (DeLong et al. (2012))

Current study shows for the first time that verbal fluency show a similar correlation among younger adults

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Thank you!Project team members:

Lauren Covey, Caitlin Coughlin, María Teresa Martínez García, Adrienne Johnson, Xiao Yang, Cynthia S. Q. Siew, Travis Major, Robert Fiorentino, and Spring 2014 Neurolinguistics II class members

Reference:

DeLong, K. A., Groppe, D. M., Urbach, T. P., & Kutas, M. (2012) Thinking ahead or not? Natural aging and anticipation during reading. Brain & Language, 121, 226-239.

Hutchison, K. A. (2007). Attentional control and the relatedness proportion effect in semantic priming. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(4), 645.

Lau, E. F., Holcomb, P. J., & Kuperberg, G. R. (2013). Dissociating N400 effects of prediction from association in single-word contexts. Journal of Cognitive Neuroscience, 25(3), 484-502.

Spreen O., Strauss E. (1998). A compendium of neuropsychological tests: Administration, norms, and commentary 2nd Edition. Oxford University Press; New York.

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Results (Cont’d)

Participants with high verbal fluency shows smaller N400 priming effect than low verbal fluency participants, when the cue is ’20% related’.

26Low VF participants, 20% related High VF participants, 20% related