Abstract: This is an experimental study of the effect of different forms of comparison (alternative contrast and successive contrast) in the teaching of arithmetic in a primary school. The results obtained show that the alternative contrast is more efficient than the successive contrast. In the light of Parlor's theory and the reflection theory of dialectical materialism, the author analyzes the data and discusses the causes of this effect. He emphasizes especially the confusion caused by similar materials and the causes for the differential effects of the two forms of comparison.

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