Table 3.

Overview of all fixed and random effects, whether they were treated as continuous variable or as factor, and their levels (in case of factors).

Effect	Species/strains	Fixed or random	Type of variable	Levels
Trial type	all	fixed	continuous and categorical	when continuous: 1 (Pos), 0.75 (NP), 0.5 (M), 0.25 (NN), 0 (Neg) when categorical: Pos, NP, M, NN, Neg
Session x Trial type	all	fixed	both continuous
Batch	all	random	categorical	1, 2
Animal ID	all	random	categorical	horses: 1–17* rats: 1–16 C57: 1–24 Swiss: 1–22*
Session	horses, rats	random	continuous	1–6
Test day	C57 & SWISS mice	random	continuous	1–4
Session per day	C57 & SWISS mice	random	categorical	1, 2
Trial type	all	random	continuous

*Only animals that fulfilled the learning criterion and that were subsequently tested in the JBT are listed here.