Investigated the variable criterion model of stimulus intensity effects. 90 female undergraduates were assigned to 5 groups. 2 groups received 3 intensities of white noise at 10-sec itis and were given either fast or slow rt feedback values with respect to a falsely established norm. A 3rd group received no feedback. Both feedback groups evidenced decreased mean rts and attenuated within-s intensity effects that persisted 24 hr. Later. Results support the variable criterion model. Feedback effects are interpreted as a lowering of s's decision criterion. To test the "neural noise" hypothesis that effects of preceding-trial stimulus intensity should decrease as iti increases, 2 additional iti groups of 6 and 15 sec. Were included. Rt was in increasing function of preceding-trial stimulus intensity; however, the sequence effects were not dependent upon iti length. (PsycINFO Database Record (c) 2006 APA, all rights reserved)