Sex Differences in the Neurocognition of Language

1. Sex Differences in the Neurocognition of Language Michael T. Ullman, Ivy V. Estabrooke, Karsten Steinhauer, Claudia Brovetto

2. Language Processing • Language Processing depends on 2 neurocognitive systems • Temporal-lobe based declarative memory system • Includes… • Mental lexicon, which contains idiosyncratic word-specific information • E.g. for irregular past tense; break-broke • Frontal/basal-ganglia procedural system • Includes… • Mental grammar underlying the real-time rule-based composition of complex linguistic representation • E.g. regular past tenses; play + ed • Also used in motor skills

3. Females are better than males at remembering words • Females tend to memorize previously encountered complex representations • E.g. regular past-tenses; played • Males generally compose it on-line • E.g. play + -ed

4. Prediction… • Both sexes should memorize idiosyncratic lexical knowledge • E.g. break-broke • Both should rule compute new complex forms • E.g. proy-ed • Why? • Because these could not be memorized

5. Previous studies • Frequency Effects • Hypothesis: if past-tense representations are retrieved from memory, more frequent ones should be remembered faster. If they are rule products, such past-tense frequency effects are not expected • 16 men and 17 women produced regular/irregular past tenses • DV: reaction-time • Men showed past tense frequency effects for irregulars but not regulars • Women showed past tense frequency effects for both verb types • Same results for both English and Spanish

6. Parkinson’s Disease • Associated with the Basal-ganglia degeneration leading to hypokinesia (suppressed movement) • Study: 15 men and 14 women with Parkinson’s disease produced past tenses • For men, past-tense production rates of regulars but not irregulars correlated with hypokinesia and production rates for irregulars but not regulars correlated with lexical abilities (object naming) • For women, production rate for both past-tense types correlated with lexical abilities but not hypokinesia • Most hypokinetic males were impaired only at regulars • Most hypokinetic women were impaired at neither

7. The Effect of Sex Hormones on Language ProcessingIvy V. Estabrooke, Kristen Mordecai, Pauline Maki, and Michale T. Ullman • As stated before, women are better than men at remembering words • This advantage appears to depend upon the temporal-lobe declarative memory system • Hypothesis: Because of women’s superior lexical/declarative memory ability, girls and women may tend to memorize and/or retrieve at least certain complex representations that men composed on-line

8. From this, two questions arise • 1. Do females memorize complex forms at a higher rate than males and/or do both sexes store tense forms, while females have superior lexical retrieval/processing abilities • 2. Do sex hormones, and estrogen in particular, contribute to the sex differences? • Previous data supports this hypothesis • Estrogen improves word and declarative memory abilities in women; more over, this improvement depends on the part of the temporal lobe that underlies declarative memory • Furthermore, testosterone improves men’s word memory

9. Methods • 10 post-menopausal women and 12 age-matched men participate in study of the effects of hormone therapy on language processing • Subjects were given hormone replacement therapy • Women-estrogen, Men-testosterone, and placebo group • After each three months, subjects were given past-tense production task containing… • Regular (sway-swayed) , irregular (break-broke), novel regular (plag-plagged) and novel irregular (spling-splung) • Verbs were presented in sentence contexts • E.g. Every day I sleep in bed. Yesterday, I ________ in bed. • Accuracy was the DV

10. Results • Hormone therapy yielded increased estrogen levels in both sexes • It also induced an increase in both sexes in the production rate of real and novel irregular past tenses • Performance at novel regulars decreased with hormone therapy in both sexes • Likely due to an increased irregularizations (plag-plog) • Accuracy at real regulars INCREASED in women but DECREASED in men, as a result of hormone therapy

11. Accuracy at Past Tense Production

12. Analysis • Increase in both women and men in production rate of real/novel irregular past-tense forms suggests that sex hormones improve the retrieval/processing of existing memorized lexical representations • And of novel forms whose processing depends on preexisting similar memory traces • E.g. fling-flung, wring-wrung

13. The decrease in performance of novel regulars with hormone therapy in both sexes.. • Supports view that these forms are computed by neural mechanisms distinct from those that underlie the processing of real and novel irregulars • It also supports the dual-system “declarative/procedural model”

14. The fact that hormone therapy led to an increase in the production rate of regular past-tenses in women, but a decrease in men shows that in women these forms patttern with the mempry-dependent irregulars and in men, they pattern with the compositional novel regulars

15. Conclusion • The sex differences just observed may be attributable to the prior memorization of complex forms by girls • This may be explained by sex-differences in estrogen levels, which could affect brain organization in utero and or learning during childhood