Summation is the usual result in composition procedures with excitatory stimuli. However, summation is difficult to obtain in autoshaping with pigeons. The problems with this preparation have been related to the stimuli used: combinations of intramodal conditioned stimuli (CSs). During the perceptual processing of this type of stimuli, some mutual interference may occur between the simple CSs of the compound. The present study tests different ways of avoiding such perceptual interaction. Experiment 1 used a serial compound but did not produce evidence of summation. Experiment 2 used a compound of blinking stimuli and did yield evidence of summation. Experiment 3 provided further evidence of summation with a compound of blinking stimuli and showed that the effect depended on the training procedure being discriminative and did not depend on the moment at which the summation test was performed, either during acquisition or during the steady state. These results suggest that perceptual interactions can be avoided with intermittent stimuli. We suggest that such stimuli could be used in autoshaping procedures that involve composition (and decomposition) of stimuli. (Contains 6 figures.)