The effects of flooding on reducing snake fear in rhesus monkeys: 6-month follow-up and further flooding

Seven wild-reared rhesus monkeys were given two different 6-month follow-up tests to assess for spontaneous recovery of snake fear that had been somewhat reduced following 7 flooding sesions 6 months earlier. Both tests revealed essentially complete spontaneous recovery of fear. In addition, all 7 monkeys received 4 further mixed flooding sessions that involved exposure to real, toy and model snakes, and the 4 most fearful monkeys also received 3 more hours of exposure to the real snake alone. A final behavioral test following these additional flooding sessions revealed a pattern of changes very similar to that observed after the original 7 sessions 6 months earlier. In particular, there were some significant changes in the behavioral avoidance component of the fear but no changes in the behavioral disturbance component of the fear. The results are discussed in the context of earlier studies that purported to demonstrate that snake fear is easy to abolish. It is concluded that these earlier studies erred by not having tests for spontaneous recovery and by only testing for changes in the behavioral avoidance component of fear. Possible reasons for the failure to produce significant changes in the behavioral disturbance component of fear are discussed.