Jumping at Shadows

This chapter introduces a psychological mechanism that involves a close link between perception and motor behaviour. It focuses on a mechanism called the brain stem reflex, which refers to a process whereby an emotion is aroused in a listener because an acoustic feature — such as sound intensity or roughness of timbre — exceeds a certain cut-off value for which the auditory system has been designed by natural selection to quickly alert the brain. It is a kind of ‘override’ system, which is activated when an event seems to require first-priority attention. Brain stem reflexes are said to be ‘hard-wired’: they are quick, automatic, and unlearned.