Nonspecific Effects of Normal Aging on Taxonomic and Thematic Semantic Processing

ABSTRACT

Objective

This study aimed to assess the effect of normal aging on the processing of taxonomic and thematic semantic relations.

Method

We used the Visual-World-Paradigm coupled with eye-movement recording. We compared performance of healthy younger and older adults on a word-to-picture matching task in which participants had to identify each target among semantically related (taxonomic or thematic) and unrelated distractors.

Results

Younger and older participants exhibited similar patterns of gaze fixations in the two semantic conditions. The effect of aging took the form of an overall reduction in sensitivity to semantic competitors, with no difference between the taxonomic and thematic conditions. Moreover, comparison of the proportions of fixations between the younger and older participants indicated that targets were identified equally quickly in both age groups. This was not the case when mouse-click reaction times were analyzed.

Conclusions

Findings argue in favor of nonspecific effects of normal aging on semantic processing that similarly affect taxonomic and thematic processing. There are important clinical implications, as pathological aging has been repeatedly shown to selectively affect either taxonomic or thematic relations. Measuring eye-movements in a semantic task is also an interesting approach in the elderly, as these seem to be less impacted by aging than other motor responses.

Acknowledgments

We wish to thank all the participants for their endless patience and their readiness to devote such effort to this study. We are also grateful to Sylvain Letellier for his technical support and IT development, and to Elizabeth Portier for the English translation.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Notes

1. Lmer structure of Level 2 models tested in the taxonomic and thematic conditions: model < -lmer(fixation~(intercept+linear+quadratic+cubic+quartic) * (Group*Object*Condition) + (intercept+linear+quadratic+cubic+quartic|Participant) + (intercept+linear+quadratic+cubic+ quartic|Participant:Condition:Object).

Additional information

Funding

This work was supported by the Rennes Clinical Neuroscience Institute (INCR; 2015 RSP-SD project on residual semantic processing in semantic dementia and elderly). The grant from the institute allowed us to fund a research engineer and a computer scientist.