Newly-Learned Stimuli: The Effects on Lateralized Lexical DecisionTravellia Tjokro & Christine Chiarello

University of California, Riverside

Introduction

Conclusions Method Exp. 1 The finding that the left visual field had a significant priming advantage compared to the right visual field may point to the possibility that lvf/RH has an advantage in newly-learned materials.

The absence of an lvf/RH advantage in Exp. 1 and the presence of lvf/RH advantage in priming in Exp. 2 suggests the possibility that the RH may be more likely to be advantaged when the newly-learned stimuli are presented along with more familiar primes, which may serve as scaffolds for the newly-learned stimuli.

The right hemisphere may have a functional role in new word acquisition. The use of semantic priming seems to be a promising technique to gauge its involvement.

* It has been proposed that the two hemispheres have different styles of coding information (Beeman, 1998).

Right hemisphere - coarse coding style. Advantage: Better activation of distant semantic relations. Disadvantage: Poor performance on selection of one, precise response.

Left hemisphere - fine coding style. Advantage: Better performance when one, precise response need to be selected. Disadvantage: Distant semantic relations are not maintained.

•Lateralized lexical decision studies have found: Nonwords showed no hemispheric asymmetry (e.g.: Leiber, 1976; Chiarello, Senehi, & Soulier, 1986; Measso & Zaidel, 1990). Word stimuli showed rvf/LH advantages (e.g.: Leiber, 1976; Weems & Zaidel, 2005). Unfamiliar & newly-learned words showed lvf/RH advantages (e.g.: Ince & Christman, 2002).

•Current studies required the participants to learn new words, and then the participants were tested on a version of lateralized lexical decision task in order to investigate whether the right hemisphere was advantaged or processing the newly-learned words. •According to the differential hemispheric coding style proposition, newly-learned words would be advantaged in the right hemisphere because coarse coding allows more semantic connections to be made.

Referenceso Beeman, M. (1998). Coarse semantic coding and discourse comprehension. In M. Beeman & C. Chiarello (Eds.), Right hemisphere language comprehension (pp. 255-284). Mahwah, NJ: Lawrence Erlbaum Associates.o Chiarello, C., Senehi, J., & Soulier, M. (1986). Viewing conditions and hemisphere asymmetry for the lexical decision. Neuropsychologia, 24(4), 521-529.o Ince, E., & Christman, S. D. (2002). Semantic representations of word meanings by the cerebral hemispheres. Brain and Language, 80, 393-420.o Leiber, L. (1976). Lexical decisions in the right and left cerebral hemispheres. Brain and Language, 3, 443-450.o Weems, S. A., & Zaidel, E. (2005). Repetition priming within and between the two cerebral hemispheres. Brain and Language, 93, 298-307.

PARTICIPANTS:• 24 male, 24 female right-handed native English speakers

TASKS:• Encoding Phase (semantically & orthographically-based encoding).

o SURK is a pajama worn by a baby dwarf.o Is SURK worn by a grandfather? - semantic o Is there a vowel in SURK? - orthographic

• Lateralized lexical decision.o English words, semantically-encoded nonwords, orthographically-encoded nonwords, never before seen nonwords.o Participants responded by pressing “Yes” for English words, and “No” to all others.

Fig. 1A & 1B

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EXP. 1

Lateralized lexical decision Phase: As seen in Fig. 1A&B, all stimuli, including the newly-learned words, produced rvf/LH advantages.

Exp. 2 was conducted for the following reasons: To obtain a more stringent measure of a participant’s learning of the new words by incorporating a forced choice recognition test. To take into account the advantageous effects of memory consolidation by conducting the experiment over 2 days. To obtain a more sensitive measure of a new word’s establishment in a participant’s lexicon by utilizing a semantic priming paradigm.

EXP. 2 Accuracy of Related and Unrelated Prime Conditions

Prime conditions did not significantly differ from one another (p = 0.3). Visual field performance differed significantly (p = 0.002). - rvf/LH is more accurate than lvf/RH. Interaction between visual field and prime conditions was significant (p = 0.04) - See Fig. 2.

Results Exp. 1

RT of Related and Unrelated Prime Conditions Prime conditions did not significantly differ from one another (p = 0.2). Visual field performance differed significantly (p = 0.001). - rvf/LH was faster than lvf/RH.Interaction between visual field and prime conditions was not significant (p = 0.4).Method Exp. 2 (2-Day)

PARTICIPANTS:• 24 male, 24 female right-handed native English speakers

TASKS:• Encoding Phase (Day 1)- similar to Exp. 1, without orthographically-based encoding• Forced-choice (Day 1 & 2).

What is a pajama worn by a baby dwarf? SURK vs. LILE (both choices were studied before).

•Lateralized lexical decision with semantic priming (Day 2).o Targets: Semantically-encoded nonwords & nonwords never before seen.o Primes: English words with related and unrelated meanings (e.g.: Related prime for SURK is ROBE, Unrelated prime is CHICK).o Participants responded “Yes” to the newly-learned words, and “No” to never before seen words.

Results Exp. 2

Fig. 2

Related vs. Unrelated Prime Comparison - Accuracy

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Fig. 1B - Reaction Times

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Fig. 1A - Accuracy

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Acknowledgement

Research supported by NIDCD grant 5R01DC6957