Signal detection theory and the effects of severe head injury upon recognition memory

Previous reports by Brooks (1974a, 1974b) employed the techniques of signal detection theory to analyse the effects of severe head injury upon recognition memory. The arguments contained in these papers are criticized with specific reference to the validity of the parameters of signal detection theory as indices of sensitivity and response bias. It is suggested that, when the theory is applied in an appropriate manner, severe head injury is shown to produce an impairment of recognition sensitivity with no concurrent change in response bias. The use of theory neutral procedures for evaluating sensitivity and response bias leads to the same conclusion.