. Author manuscript; available in PMC: 2010 Mar 1.

Published in final edited form as: Psychopharmacology (Berl). 2008 Oct 17;203(1):33–40. doi: 10.1007/s00213-008-1367-5

Table 1.

Pattern matrices for the principal components analyses of the indices of reinforcement generated from an alcohol purchase task

Index	Observed values		Derived values
	Component		Component
	Factor 1	Factor 2	Factor 1	Factor 2
Elasticity	0.95	−0.09	0.94	−0.24
Breakpoint	0.88	0.12	0.88	0.18
P_max	0.90	−0.07	0.93	−0.24
O_max	0.48	0.65	0.85	0.34
Intensity	−0.14	0.99	−0.02	0.99

Analyses were conducted separately for observed and derived values for P_max, O_max, and intensity of demand. A criterion of 0.30 was used to determine whether an index significantly loaded on a factor