Editing G factor (psychometrics) (section)

===Elementary cognitive tasks===
{{Main|Elementary cognitive task|Mental chronometry}}
[[Image:Jensen box.gif|right|thumb|300px|An illustration of the [[Jensen box]], an apparatus for measuring choice reaction time]]
Elementary cognitive tasks (ECTs) also correlate strongly with ''g''.<!--{{Citation needed|reason=Really? According to whom? What?|date=September 2010}} See reference below.--> ECTs are, as the name suggests, simple tasks that apparently require very little intelligence, but still correlate strongly with more exhaustive intelligence tests. Determining whether a light is red or blue and determining whether there are four or five squares drawn on a computer screen are two examples of ECTs. The answers to such questions are usually provided by quickly pressing buttons. Often, in addition to buttons for the two options provided, a third button is held down from the start of the test. When the stimulus is given to the subject, they remove their hand from the starting button to the button of the correct answer. This allows the examiner to determine how much time was spent thinking about the answer to the question (reaction time, usually measured in small fractions of second), and how much time was spent on physical hand movement to the correct button (movement time).  Reaction time correlates strongly with ''g'', while movement time correlates less strongly.<ref>Jensen 1998, 213</ref>
ECT testing has allowed quantitative examination of hypotheses concerning test bias, subject motivation, and group differences.  By virtue of their simplicity, ECTs provide a link between classical IQ testing and biological inquiries such as [[fMRI]] studies.