Table 2. Model comparison and selection.

The first column specifies which mean parameter estimates were allowed to vary freely between dose groups. The row labeled None corresponds to the model in which all mean estimates were fixed. RSS is the residual sum of squares over all subjects, k is the number of free parameters in the model. As each model was fitted to individual subject data, a set of free parameters was estimated for each dose group. AICc=2k+nln (RSS/n) + [2k(k+1)/(n−k−1)], where n is the total number of observations = 21 rats × 20 sessions = 420. Data for the model with the lowest AICs are underlined and signify the selected model.

Model	RSS	k	ΔAICc
None	9031.94	79	48.51
A	8421.96	81	25.27
B	8879.97	81	47.51
h	8691.84	81	38.51
A, B	8352.18	83	27.97
A, h	7814.06	83	0.00
B, h	8581.68	83	39.36
A, B, h	7779.75	85	4.42