Individual assessment profiles of the 8 animals that participated readily enough in the tasks to be assessed longitudinally. The first two rows represent the five irradiated animals. The bottom row represents the three control animals. The “+” indicates that either the session was terminated prior to completion, or more than half of the trials were not attempted: i.e., for “+” located below the x-axis, the session was terminated prior to completion and fewer than 15 trials were attempted; and for “+” located at the animal’s overall accuracy for that trial as a function of number of trials attempted, the session was terminated prior to completion, but 15 or more trials were attempted. *Technical error wherein a reversal was given after only three consecutive 90% accuracy sessions instead of four. Dotted vertical lines indicate point of reversal, hashed lines indicate point of re-reversal and solid lines indicate completion of stimulus pair.