Attenuated Hemispheric Asymmetry in Metaphor Processing Among Adults With ADHD

Objective: To characterize the hemispheric processing of metaphors in adults with ADHD compared
to controls. Method: We investigated the hemispheric processing of metaphors in 24 adult participants
diagnosed with ADHD and 24 control participants. The hemispheric processing was examined
using a divided visual field paradigm, in which different kinds of metaphors as well as literal word
pairs and unrelated word pairs were presented either to the right visual field/left hemisphere
(RVF/LH) or to the left visual field/right hemisphere (LVF/RH). Results: Control participants
processed metaphors more efficiently when presented in the LVF/RH than when presented in the
RVF/LH, whereas participants with ADHD demonstrated attenuated asymmetry of hemispheric
processing. Furthermore, asymmetry of hemispheric processing, together with sustained attention,
contributed significantly to the prediction of self-report of ADHD symptoms. Conclusion: Our
results suggest that the hemispheric processing of adults with ADHD is less lateralized than the
hemispheric processing of control participants. Moreover, the diminished lateralization of metaphor
processing along with deficient sustained attention may reflect distinct cognitive mechanisms
underlying ADHD and as such our results support multiple pathway models of ADHD.