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CHAPTER 5 132 Threat expectancy Figure 1 shows that Pavlovian acquisition occurred. At the end of the Pavlovian acquisition phase, threat expectancy differed between A, B, and C, F (1.41,41.01) = 706.30, p < .001, η p 2 = .96. Threat expectancy for B was lower than for A, t (29) = 28.02, p < .001, d = 8.47, and for C, t (29) = 28.62, p < .001, d = 8.25. It was comparable for A and C, t < 1. The introduction of safety behavior in the Safety behavior acquisition phase immediately decreased threat expectancy for A; A+ vs. first A*(+), t (29) = 8.85, p < .001, d = 2.20; and for C; C+ vs. first C*(+), t (29) = 8.13, p < .001, d = 1.94. In the Extinction phase, threat expectancy for A and C declined in a linear trend F (1,29) = 421.36, p < .001, η p 2 = .93, with a quadratic component, F (1,29) = 106.43, p < .001, η p 2 = .79. This trend did not significantly differ between A and C, F < 1. Threat expectancy for B initially increased in the Extinction phase: Safety behavior acquisition phase B- vs. first Extinction phase B-, t (29) = 4.28, p < .001, d = 1.11. Then it declined in a linear trend, F (1,29) = 15.19, p = .001, η p 2 = .34. At the end of the Extinction phase, there were no significant differences in threat expectancy between A, B, and C, F < 1. At the beginning of the Return of safety behavior phase, threat expectancy increased for A: final Extinction phase A- vs. first Return of safety behavior phase A-, t (29) = 2.55, p = .02, d = 0.60; and for B: final Extinction phase B- vs. first Return of safety behavior phase B-, t (29) = 2.13, p = .04, d = 0.40; but not for C: final Extinction phase C- vs. first Return of safety behavior phase C*-, t < 1. Threat expectancy subsequently declined in a linear trend for A, F (1,29) = 9.00, p = .005, η p 2 = .24, but not significantly for B, F (1,29) = 2.16, p = .15. However, at the end of the Return of safety behavior phase there were no significant differences between A, B, and C, F (2,58) = 1.31, p = .28. Finally, the change in threat expectancy from the final Return of safety behavior trial to the Test phase differed between A, B, and C, F (2,58) = 5.49, p = .007, η p 2 = .16. There were no main effects of Trial and Stimulus, both F s < 1. Threat expectancy did not change for A, t < 1, and B, t (29) = 1.02, p = .31, but it increased for C, t (29) = 2.67, p = .01, d = 0.70.