Additionally when the pH was altered in coculture flasks using HCl (10 mM) or NaOH (10 mM) further declines were seen, yielding 7 day ratios of 1∶0.005 and 1∶0.0006, respectively. Moreover, that theory has been highly productive of research in numerous areas (linguistics, psycholinguistics, developmental psychology, second language research, speech pathology etc. etc.) over the last 50 years. Perhaps unsurprisingly, we found none of the chemicals tested resulted in an increase in σS expression.