Research is reported on the cognitive mediational paradigm which postulates that teachers influence students' learning by causing them to think and behave in particular ways during teaching. Four studies are reported. The first describes five teachers and their students and explores, in classroom lessons, the cognitive processes students used in response to teaching and the cognitive processes their teachers intended them to use. The second and third studies employ analogs of classroom teaching in the form of short videotaped lessons. These sought to determine if elementary school students could be trained to perceive and act on common instructional stimuli and whether these operations would facilitate learning. The fourth study constituted an extension of the second and third studies to regular classroom environments. Three major conclusions are offered: (1) Students and teachers operate in ways that reflect the mediating role of students' cognition in classroom learning; (2) Students can be trained to discriminate instructional stimuli and respond with pre-arranged cognitive strategies; and (3) Students' achievement is partly a function of cognitive strategies they activate in response to instructional stimuli perceived during teaching. Methodological issues attendant to the studies are discussed. (Author/JD)