Table 2 Significance of effects and hazard ratios for effects used in Cox proportional hazards model (complete model enabling inclusion of multiple predictor variables and interaction terms) for sessions to pass the initial discrimination and reversal learning stage, for calves provided different reward types (Aim 1) and subject to different social housing treatments and reward types (Aim 2).

	Stage	Effect	Reference levels			HR (95% CI)^a	χ2	P-value
Aim 1	Initial	BW	+ 1 kg	–	–	1.3 (1.1,1.5)	13.6	< 0.001
		Reward	–	–	–	–	7.5	0.02
			Exit	Food	–	2.9 (0.7,11.9)	2.3	0.13
			Exit	Social	–	0.5 (0.2,1.3)	2.1	0.15
			Food	Social	–	0.2 (0.04,0.6)	7.3	0.007
	Reversal	BW	+ 1 kg	–	–	0.8 (0.7,1.0)	4.6	0.03
		Reward	–	–	–	–	4.2	0.12
			Exit	Food	–	2.3 (0.4,14.2)	0.8	0.37
			Exit	Social	–	4.1 (1.1,16.4)	4.1	0.04
			Food	Social	–	1.8 (0.4,8.3)	0.6	0.45
Aim 2	Initial	BW	+ 1 kg	–	–	1.2 (1.1,1.3)	7.9	0.005
		Housing	–	–	–	–	2.7	0.10
		Reward	–	–	–	–	2.3	0.13
		Interaction^†	–	–	–	–	4.7	0.03
			Individual	Pair	Exit	0.4 (0.1,1.2)	2.7	0.10
			Individual	Pair	Social	2.3 (0.7,7.5)	2.0	0.16
			Exit	Social	Individual	0.4 (0.1,1.3)	2.3	0.13
			Exit	Social	Pair	2.4 (0.8,7.2)	2.5	0.11
	Reversal	BW	+ 1 kg	–	–	0.8 (0.7,1.0)	4.9	0.03
		Housing	–	–	–	–	0.6	0.46
		Reward	–	–	–	–	6.0	0.01
		Interaction^b	–	–	–	–	2.2	0.14
			Individual	Pair	Exit	1.6 (0.5,5.9)	0.6	0.46
			Individual	Pair	Social	0.4 (0.1,1.4)	2.1	0.15
			Exit	Social	Individual	6.0 (1.4,24.9)	6.0	0.01
			Exit	Social	Pair	1.4 (0.3,6.5)	0.2	0.66

^aHR (95% CI) = hazard ratios within variable with 95% confidence intervals (lower, upper).
^bInteraction between reward type and previous housing treatment.

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