Nettelbeck, T.Zwalf, O.Stough, C.Sternberg, R.J.2021-08-312021-08-312020The Cambridge Handbook of Intelligence, 2020 / Sternberg, R.J. (ed./s), Ch.20, pp.471-50311087191989781108719193http://hdl.handle.net/2440/131767Research on human intelligence from a psychological perspective has mainly focused on higher-order cognitive abilities leading to the development and validation of psychometric measures of intelligence such as the IQ test. Despite the success of this movement, there is a lack of understanding on how intelligence measured by IQ tests develops. As such, recent research has focused on studying the basic underlying processes of intelligence. These measures are often referred to as measures of processing speed and collectively as elementary cognitive tasks (ECTs). In this chapter, we review research on two of the most prominent ECTs found in the intelligence literature: reaction time (RT) and inspection time (IT). We describe these measures and variants of these measures in detail and report on studies examining relationships between RT, IT, and intelligence. We describe theories relating to these measures and attempt to understand whether relationships between RT, IT, and intelligence are best described by top-down (strategic) or bottom-up (basic) processes. We outline exciting new areas using pharmacological and neuroimaging techniques that could contribute to this body of knowledge.en© Cambridge University Press 2020Book chapter100003291110.1017/9781108770422.0212-s2.0-85098303599561735