Can cerebral lateralisation explain heterogeneity in language and increased non-right handedness in autism? A literature review.
Atypical brain sidedness helps explain scattered language skills in autism, but handedness is a poor clue.
01Research in Context
What this study did
Camodeca et al. (2020) read every paper they could find on brain sidedness in autism. They asked two questions: does odd lateralisation explain why some autistic kids speak fluently while others stay non-verbal, and does it also explain why more autistic people are left-handed or ambidextrous.
The team pulled studies that used MRI, EEG, or handedness checklists. They did not run new scans; they simply stitched together what others had published.
What they found
The review shows a clear pattern: autistic brains often shift language areas away from the classic left side. This shift lines up with the wide scatter of language skills seen on the spectrum.
The handedness link is shakier. Some papers find more left-handers, others do not, so the jury stays out.
How this fits with other research
Bhaumik et al. (2009) looked at a different brain marker—event-related potentials—and also found sensory wiring differences. Together the two reviews say autism shows up at multiple brain levels, not just one.
McIntyre et al. (2002) tested right-hemisphere tasks in Asperger cases and found deficits; Amy’s review adds that the whole left-right setup can be flipped or mixed, giving a fuller picture of why tasks like reading faces and using words do not travel together.
Iosa et al. (2012) used PET scans and saw extra blood flow in limbic and cerebellar regions. Their metabolic angle dovetails with Amy’s structural angle: autistic brains differ in both layout and activity.
Why it matters
When a child scores low on standard language tests, do not assume global delay. Probe which hemisphere is doing the talking work. If the right side has taken over, visual supports or melody cues may work better than verbal prompts. Also, stop treating left-handedness as a red flag; it is not a reliable autism marker on its own.
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02At a glance
03Original abstract
BACKGROUND: Autism is characterised by phenotypic variability, particularly in the domains of language and handedness. However, the source of this heterogeneity is currently unclear. AIMS: To synthesise findings regarding the relationship between language, handedness, and cerebral lateralisation in autistic people and consider how future research should be conducted in order to progress our understanding of phenotypic variability. METHODS AND PROCEDURES: Following a literature search and selection process, 19 papers were included in this literature review. Studies using behavioural, structural, and functional measures of lateralisation are reviewed. OUTCOMES AND RESULTS: The studies reviewed provided consistent evidence of differential cerebral lateralisation in autistic people, and this appears to be related to between-group differences in language. Evidence relating this to handedness was less consistent. Many of the studies did not include heterogeneous samples, and/or did not specify the language process they investigated. CONCLUSIONS AND IMPLICATIONS: This review suggests that further research is needed to fully understand the relationship between cerebral lateralisation and phenotypic variability within autism. It is crucial that future studies in this area include heterogeneous samples, specify the language process they are investigating, and consider taking developmental trajectories into account.
Research in developmental disabilities, 2020 · doi:10.1016/j.ridd.2020.103738