ABSTRACT
The purpose of Experiment I was to assess children's ability to draw valid conclusions from given premisses in a specific reasoning situation. The 128 tasks resulted from 14 experimental formulas plus 2 catch formulas, 4 interpretations of each of the 16 formulas, and 2 different versions of each task. Every subject received every task. To ensure that the problems genuinely required logical inference for their solution and not simply a perceptual or mnemonic search, the test materials about which the inferences were to be made were kept hidden during the problems. The procedure also prevented the subjects from memorizing the stimulus display and then attempting to produce the correct answer by examining a mental image. The decision to include more subjects, and the decision as to when to terminate the experiment, were both made prior to any data analysis beyond determining the overall success-rate.
