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. Author manuscript; available in PMC: 2015 Jan 1.
Published in final edited form as: J Exp Anal Behav. 2013 Sep 30;101(1):10–25. doi: 10.1002/jeab.51

Fig. 2.

Fig. 2

Comparison-response rates in pecks per s (± 1 SEM) on the hue–form arbitrary matching baseline trials (open circles) and the nonreinforced form–hue symmetry probe trials (filled circles) averaged over the eight test sessions for each Control Group pigeon. “Positive” = reinforced arbitrary baseline trials and test trials in which the samples and comparisons of the reinforced baseline trials were reversed. “Negative” = non-reinforced arbitrary baseline trials and test trials on which the samples and comparisons of the nonreinforced baseline trials were reversed.