Dissociative Effects of Prime Duration, Lexicality, and Word Frequency in Lexical Decision
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Dissociative Effects of Prime Duration, Lexicality, and Word Frequency in Lexical Decision Mary L. Still Alison L. Morris Iowa State University. Experiment 2: High N Stimuli. Orthographic Priming. Experiment 1: Low N Stimuli.

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Dissociative Effects of Prime Duration, Lexicality, and Word Frequency in Lexical DecisionMary L. Still Alison L. MorrisIowa State University

Experiment 2: High N Stimuli

Orthographic Priming

Experiment 1: Low N Stimuli

  • Orthographic priming has been used to investigate word recognition.

  • The logic is that processing of one item will facilitate or inhibit the

  • processing of a subsequent similar item. Recently orthographic priming

  • experiments have focused on testing models of word recognition, but

  • several issues remain problematic (Davis, 2003).

  • Potentially Problematic Findings – Lexical decision

  • Frequency effect(Segui & Grainger, 1990)

    • Masked primes: higher freq primes interfere with lower freq targets

    • Unmasked primes: lower freq primes interfere with higher freq targets

  • Neighborhood Density Constraint(e.g., Forster & Davis, 1991)

    • Orthographic priming occurs for targets with few neighbors (low density), but not for targets with many neighbors (high density)

    • Models of word recognition do not predict a difference

  • Prime Duration(Davis, 2003)

    • Models of word recognition predict that priming increases as prime exposure duration increases

    • Human results do not follow this pattern

  • Research Questions

  • Can interference effects be explained without lexical inhibition?

  • Can the frequency effect be explained without assuming differences between masked and unmasked priming?

  • Why is facilitation not found for High N targets?

  • Current Experiments – Experiment 1 extends Davis and Lupker’s (2006) Experiment 1 using their design and stimuli (replacing a few items). Experiment 2 has the same design but used high N stimuli.

Frequency N


High freq 176 10.3

Low freq 8 10.3

Nonwords ---- 9.3

Shared Neighbors Exp 1 Exp 2

Word-Word .38 3.41

NW – HF .06 3.84

NW – LF .08 3.98

CMOP Prediction – High N stimuli

will produce interference because

they are well encoded


* Interference effects were ubiquitous

* Marginally sig. interference for

HF targets preceded by nonword


* Priming is not obtained for High N

stimuli because they tend to

produce interference

Frequency N


High freq 366 2.4

Low freq 5 2.2

Nonwords --- 2.9

* All sig. subject results are sig. in the

item analysis as well

* Differences > zero represent

facilitation; differences < zero

represent interference


* The most pronounced lexicality

effect emerged at 250ms

* Replicated the frequency

effect, but it seems unlikely the

reversal in interference effects is

tied to prime awareness

* Priming effects seem to depend

on prime exposure duration as

opposed to awareness of the


Competition Model of Orthographic Priming


Computational model of repetition effects, originally implemented to predict and explain common repetition blindness findings (Morris, Still, & Caldwell-Harris,2007).

Benefit of Repetition

Repetition always results in a “cleaner” representation – higher signal to noise ratio. If the item is processed well the first time, repetition leads to less summed neural activation of the representation.

Costs of Repetition

Items compete for awareness based on summed neural activity; items with more activity outcompete those with less activity.

Strength of this Model

Accounts for lexicality, frequency, and prime duration effects in masked priming via two simple constructs – stimulus encoding and competition.


Prime Type


Ortho N Control Ortho N Control

Word Targets (96 trials)

High Freqaxle – ABLE thug – ABLE ible – ABLE shug – ABLE

Low Freqable – AXLE door – AXLE axue – AXLE doir – AXLE

Nonword Targets (48 trials)

duet – DUIT self – DUIT duin – DUIT sulf – DUIT

Lexicality Effect Frequency Effect

CMOP predicts this pattern of results without using lexical inhibition. Stimulus

encoding and prime-target competition are hypothesized to account for these results.

Primes that are poorly encoded (e.g., nonwords, LF words, Low N stimuli) tend to

produce facilitation, while primes that are better encoded (e.g., words, HF words,

High N stimuli) tend to produce interference earlier, i.e., with shorter prime durations.

In future versions of CMOP we intend to include a decision criterion so that both RTs

and error rates can be simulated. This will allow for more detailed analyses of CMOP.

Procedure: Lexical Decision


Davis, C. J., (2003). Factors underlying masked priming effects in competitive network models of visual word

recognition. In S. Kinoshita & S. J. Lupker (Eds.), Masked Priming: The State of the Art. New York:

Psychology Press.

Davis, C. J., & Lupker, S. J. (2006). Masked inhibitory priming in English: Evidence for lexical inhibition.

Journal of Experimental Psychology: Human Perception and Performance, 32, 668-687.

Forster, K. I., & Davis, C. (1991). The density constraint on form-priming in the naming task: Interference effects

from a masked prime. Journal of Memory and Language, 30, 1-25.

Morris, A. L., Still, M. L., & Caldwell-Harris, C. L. (2007). Repetition blindness: An emergent property of

inter-item competition. Manuscript submitted for publication.

Segui, J., & Grainger, J. (1990). Priming word recognition with orthographic neighbors: Effects of relative prime-

target frequency. Journal of Experimental Psychology: Human Perception and Performance,16, 65-76.


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