Measurement and modification of delusional beliefs.

It has been proposed that delusional thinking may be on a continuum with normal behavior and can be assessed by taking account of factors such as the client's degree of belief conviction or the extent of preoccupation with the belief. In our research a number of measures were used to assess the delusional thinking of people diagnosed as schizophrenic. Two interventions were used: (a) a structured verbal challenge and (b) a reality test in which the belief was subject to an empirical test. We used a multiple-baseline, across-subjects design. Of the 6 clients, 2 completely rejected their beliefs, and 3 others significantly reduced their belief conviction. Maintenance was good, and there was evidence that the intervention had enabled 5 of the 6 clients to effectively regulate their delusional thinking.