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. Author manuscript; available in PMC: 2017 Apr 1.
Published in final edited form as: J Exp Psychol Anim Learn Cogn. 2016 Feb 15;42(2):141–162. doi: 10.1037/xan0000097

Figure 7.

Figure 7

Difference in the discounting rate parameter (k) between smaller and larger delayed amounts in individual rats (dark triangles) and pigeons (grey circles) across four studies using an adjusting-amount procedure. Data are from “Determination of discount functions in rats with an adjusting-amount procedure” by J. B. Richards, S. H. Mitchell, H. de Wit, and L. S. Seiden, 1997, Journal of the Experimental Analysis of Behavior, 67, pp. 353–366, “Discounting of delayed food rewards in pigeons and rats: Is there a magnitude effect?” by L. Green, J. Myerson, D. D. Holt, J. R. Slevin, and S. J. Estle, 2004, Journal of the Experimental Analysis of Behavior, 81, pp. 39–50, “Delay discounting of qualitatively different reinforcers in rats” by A. L. Calvert, L. Green, and J. Myerson, 2010, Journal of the Experimental Analysis of Behavior, 93, pp. 171–184, and “Pigeons’ delay discounting functions established using a concurrent-chains procedure” by L. Oliveira, L. Green, and J. Myerson, 2014, Journal of the Experimental Analysis of Behavior, 102, pp. 151–161.