An intervention procedure designed to enhance the perceptual salience of an odd stimulus is described which enabled four developmentally delayed children to succeed at a subsequent difficult reversal shift discrimination. None of the children were able to successfully perform this classic oddity task prior to the intervention. While the chronological age of the children (all below ufor years of age) would lead to their being classified in a "preoperational" stage developmentally, the present data suggest that a sufficiently salient perceptual intervention can induce successful oddity performance. As an alternative to the traditional mediational stage models, the child's detection of invariant relational information present in the visual array itself is forwarded as the most parsimonious explanation.