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. Author manuscript; available in PMC: 2012 Apr 15.
Published in final edited form as: Neuroimage. 2011 Jan 19;55(4):1878–1888. doi: 10.1016/j.neuroimage.2011.01.041

Figure 1. Stimulus set and task design.

Figure 1

(a) The stimulus dimension consisted of 5 images, of the same identity, morphed between neutral and fearful endpoints. (b) The task involved rating whether each face was or was not expressing fear by pressing one of two buttons. In the first phase (preconditioning), subjects saw each morph increment in the absence of the US. Fear learning involved repeated pairings of the S3 (CS+) with an electrical shock US, and the S1 (CS−) unreinforced. The generalization test followed fear learning and involved presentation of each of the morph increments. The CS+ was intermittently reinforced during the generalization test. Images are not to scale.