Table 1.

ERI (extinction retention index) definitions

ERI	Formula	Studies from which they were adapted
ERI¹	100 × [(mean first four CS⁺ retention) – (mean first four CS^– retention)]/[max pair (CS⁺)–(CS⁻) acquisition]	Method 13
ERI²	100 × [(mean first four CS⁺ recovery) − (mean first four CS⁻ recovery)]/max (CS⁺) acquisition	Dunsmoor et al. (2015a) and Milad et al. (2007)
ERI³	[mean (first four CS⁺ recovery) – mean (first four CS⁻ recovery)] − [mean (last four CS⁺ extinction) – mean (last four CS⁻ extinction)]	Methods 15 and 16^a
ERI⁴	(first CS recovery) – (last CS extinction)	Methods 9a and 9b^a

Emotional intensity produces a linear relationship on conditioned learning but an inverted U-shaped effect on episodic memory