ABSTRACTIt is suggested that a) the difference between conditioning and pseudoconditioning procedures is one involving degree of interstimulus interval variability, b) the effect of this variability is to alter the temporal characteristics of the responses generated by such procedures, c) the procedures typically employed in comparing performance levels heavily bias the results in favor of the conditioning procedure, and d) there is little or no evidence to support the view that performance differences between such groups reflect differing underlying processes, one associational and the other not. In addition, the use of CS– groups as control groups, in differential conditioning, is based upon a premise which has little, if any, suppor