Table 2.

Pair-comparison Training Contingencies in Experiment 2

R → T – Left+	Symbolic (AB)
R → H – Right+
G → T – Right+
G → H – Left+
R → R – Left+	Hue identity (AA)
R → G – Right+
G → R – Right+
G → G – Left+
T → T – Left+	Form identity (BB)
T → H – Right+
H → T – Right+
H → H – Left+

Note. R = red, G = green, T = triangle, H = horizontal, FI = fixed interval schedule, Left+ = left side-key choice reinforced, Right+ = right side-key choice reinforced. A and B denote hue and form stimulus sets, respectively. Samples are shown to the left of the arrows; comparisons are shown to the right of the arrows. Incorrect (non-reinforced) choices and counterbalancing of the symbolic left versus right contingencies are omitted for clarity.