The purpose of this study was to test the Lacey hypothesis of cardiac behavior patterns for possible use as a measure of attentiveness in a classroom where experimental variables were not controlled. Lacey's hypothesis predicted cardiac deceleration with instances of information-intake and cardiac acceleration with instances of information-processing. Third grade students in a self-contained classroom were telemetrically monitored for heart rate during reading group activities. Based on cardiac behavior, taking verbal instructions and reading aloud were improperly classified. Verbal instructions produced a mean acceleratory response instead of the predicted deceleration. Reading aloud produced a weak mean deceleratory response instead of the anticipated acceleration. The other events within the intake category and the processing category, respectively, adhered to the predicted directional responses despite their statistical nonsignificance. The methodology proved sensitive to events following the momentary state of information-handling by the individual. It was proposed that averaging of data led to loss of individual sensitivity to reading group events. Individual student attentiveness to different events may be yet studied via this objective technique.