Zener card representations were presented visually for 15 sec. every 30 sec. for a total of 40 trials per session over 17 sessions to a single subject who displayed temporal lobe lability. During the 15 sec. before the presentation of one of the symbols (target) either a specific 4-Hz magnetic field pattern or a 1-Hz or 7-Hz magnetic field was presented bilaterally at the level of the temporal lobes. Field strengths were in the order of milligauss (about 1000X background values). The subject was required to anticipate the next symbol for each trial. Only when the 4-Hz field preceded the target symbol did the subject's accuracy of guessing remain systematically above (50%) chance (20%) over the sessions. These results suggest that exogenous magnetic fields may become discriminative stimuli through temporal association. Evidence of habituation was also obtained.