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The present article discusses how events outside a subject's skin and not accessible to another subject but to an experimenter may contribute to experimental analyses of private events. Of 16 undergraduates, 8, referred to as instructors, first learned conditional discriminations (i.e., 81 C1, 82C2, 83C3, and 84C4) in a standard matching-to-sample (MTS) task with the stimuli 8s as the samples and the stimuli Cs as the correct comparisons. Then the other 8 subjects, learners, were exposed to modified MTS trials in which responses of the learnElrs were reinforced or punished not by the experimenter but by the instructors. Conditional discriminations to be established were A 1 C1, A2C2, A3C3, and A4C4, in which the sample stimuli As were presented simultaneously with the stimuli 8s so that the instructors could not see the As but only the 8s. For 2 of the 8 pairs, the learners learned the AC conditional discriminations from the instructors who were not accessible to the stimuli As. Functionally, private events have been defined by their accessibility rather than their structure (e.g., Skinner, 1953). In this context, therefore, the stimuli As may be characterized as a kind of private events within the present 2 pairs of instructors and learners.