Phonology and handedness in primary school: predictions of the right shift theory

Background:  The right shift (RS) theory of handedness suggests that poor phonology may occur in the general population as a risk associated with absence of an agent of left cerebral speech, the hypothesised RS + gene. The theory predicts that poor phonology is associated with reduced bias to right-handedness. Methods:  A representative cohort of primary school children was assessed on tests of phonology, nonverbal ability, literacy, and handedness. There were three types of analysis; for discrete variables, poor phonology and left hand preference; for continuous variables, phonology factor scores and hand skill; for ‘cases’ of specifically poor phonology. Results:  Reduced bias to dextrality was found in those with poor phonology for all types of analysis. Trends were similar for both sexes but stronger in males than females. Poor phonology was associated with a raised proportion of left-handed brothers. There was a strong association between poor phonology and poor literacy, but not all those with specifically poor phonology were poor readers or spellers. Among children with poor phonology but not poor for other variables, some 23–31% were left-handed writers. Conclusions:  Poor phonological processing is associated with reduced bias to the right hand, consistent with absence of an agent of left hemisphere advantage

Evidence for the release of long-term tectonic strain stored in continental interiors through intraplate earthquakes

The occurrence of large earthquakes in stable continental interiors challenges the applicability of the classical steady-state ‘seismic cycle’ model to such regions. Here, we shed new light onto this issue using as a case study the cluster of large reverse faulting earthquakes that occurred in Fennoscandia at 11-9 ka, triggered by the removal of the ice load during the final phase of regional deglaciation. We show that these reverse-faulting earthquakes occurred at a time when the horizontal strain-rate field was extensional, which implies that these events did not release horizontal strain that was building up at the time, but compressional strain that had been accummulated and stored elastically in the lithosphere over timescales similar to or longer than a glacial cycle. We argue that the tectonically-stable continental lithosphere can store elastic strain on long timescales, the release of which may be triggered by rapid, local transient stress changes caused by surface mass redistribution, resulting in the occurrence of intermittent intraplate earthquakes