Fig. 1.

Panels A and B show hypothetical discounting curves for relatively high (i.e., steep) and low (i.e., shallow) discount rates. Panel A depicts discounting curves as displayed on a linearly scaled x-axis, where spacing between delay values is arithmetic. Many of the shorter delays are grouped together in an indistinguishable bunch as shown in the circled area of the x-axis. Panel B depicts discounting curves on a logarithmic x-axis, where the progression of values is exponential. Note that effective delay 50 (ED50) is more easily identifiable and differences in discount rates are manifested in a location shift (i.e., left or right) along the x-axis. Panel C depicts real data from Koffarnus and Bickel (2014) for college-aged participants completing an adjusting amount discounting task showing the range of discounting rates seen with control subjects.