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Freezing as a function of heredity, vocalization, and training. Breeding line is indicated by shading (see legend), and vocalization group (silent vs. vocal in emitting ~22 kHz sounds during acquisition) is indicated by separate panels. Means are plotted as lines with 95 % confidence bands. Vocalizers showed significantly more freezing after acquisition, but not after extinction. Breeding lines were significantly different after extinction, but not after acquisition, p < .05
