The strength of the RT-IQ association is a subject of research. Several studies have reported association between simple RT and intelligence of around ("r" = −.31), with a tendency for larger associations between choice RT and intelligence ("r" = −.49). Much of the theoretical interest in RT was driven by Hick's Law, relating the slope of RT increases to the complexity of decision required (measured in units of uncertainty popularized by Claude Shannon as the basis of information theory). This promised to link intelligence directly to the resolution of information even in very basic information tasks. There is some support for a link between the slope of the RT curve and intelligence, as long as reaction time is tightly controlled.