Wait time, or think time, of three or more seconds after posing a question increases how many students volunteer and the length and accuracy of their responses. Having more time to think also increases students' Motivation to respond and supports their Short- and Long-term Memory. Waiting after hearing a student's response has also been shown to improve the quality and variety of teachers' questions, in particular increasing the number of questions that require higher-level thinking.
Watch this short clip on wait time in an elementary classroom. This teacher waits at least three seconds after posing a question on inferencing and once she is sure her students know to use the time to think versus raising their hands with an answer.