Table 1. Mathematical formulations of three- and four-parameter additive and multiplicative discounting models.

Parameters	Model	Equation	Model formula
Additive
Amount & IV scaled
3	ADD3	(6)	$SV=A-A\left(1-1/{\left(1+kD\right)}^s\right)-A\left(1-1/{\left(1+h\theta \right)}^s\right)$
4	ADD4	(7)	$SV=A-A\left(1-1/{\left(1+kD\right)}^{sd}\right)-A\left(1-1{\left(1+h\theta \right)}^{sp}\right)$
Only IV scaled
3	ADD3R	(8)	$SV=A-A\left(1-1/\left(1+k{D}^s\right)\right)-A/\left(1-1/\left(1+k{D}^s\right)\right)$
4	ADD4R	(9)	$SV=A-A\left(1-1/\left(1+k{D}^{sd}\right)\right)-A/\left(1-1/\left(1+k{D}^{sp}\right)\right)$
Multiplicative
Amount & IV scaled
3	MULTI3	(10)	$SV=A/({\left(1+kD\right)}^s*{\left(1+h\theta \right)}^s)$
4	MULTI4	(11)	$SV=A/({\left(1+kD\right)}^{sd}*{\left(1+h\theta \right)}^{sp})$
Only IV scaled
3	MULTI3R	(12)	$SV=A/\left(\right(1+k{D}^s)*(1+h{\theta }^s\left)\right)$
4	MULTI4R	(13)	$SV=A/\left(\right(1+k{D}^{sd})*(1+h{\theta }^{sp}\left)\right)$