Handedness, i.e. the asymmetry in hand preference,
with a large proportion of humans preferring the right over the left hand in
performing single-hand tasks, seems to be an exclusive feature of our species.
Self-reported hand
preference has been used as a measure of handedness, which is used, in turn, as
a proxy for hemispheric lateralization. Indeed,
the
degree of handedness, i.e. the degree of preference for the use of one hand in
performing some single-hand tasks, has been found to correlate with language
dominance, with right-handedness showing that the left hemisphere of the brain
is dominant for language.
Atypical
handedness has been repeatedly reported in schizophrenia, with quantitative
review of evidence showing an increase of non-right-handedness in patients
diagnosed with schizophrenia.
Mixed-handedness
is also higher among people without clinical diagnoses but scoring high on
questionnaires aimed at measuring psychosis-proneness, and, as well, among
those assessed as having schizotypal personality traits. Most studies in so far
were carried out in American or British samples.
A recent study
carried out by Dr Antonio Preti confirmed that in an Italian non-clinical
sample, too, the distribution of the scores on a reliable measure of
psychosis-proneness, the PDI, is related to hand preference, with mixed-handed
subjects more likely to endorse items on the PDI than both right- and
left-handed peers.
The differences
were particularly important for the Òparanoia/paranoid
disorderÓ and the Òparanormal beliefsÓ subscales.
The study of
indexes of psychosis-proneness in non-clinical samples, looking for biological
and cognitive markers of schizophrenia, might be a useful addendum to clinical
studies, since it allows the investigation of testable models without the crux
of severe psychotic symptoms and the interference due to multiple biological
effects of drug therapy.
Reference:
Preti A., Sardu
C., Piga A.
Mixed-handedness
is associated with the reporting of psychotic-like beliefs in a non-clinical
Italian sample.
Schizophrenia
Research, 2007, 92: 15-23.
Contacts:
Dr Antonio
Preti
SchizophreniaProject
e-mail: apreti@tin.it