Table 2.

Negative binomial generalised linear models showing the direction of effects and the significance level of the terms in the underwater photos and drawings discrimination

Response variable	Model	Minimal model	Average effect	SE	Wald statistic	z	p value
Number of sessions to criterion	Model 1	Stimulus group: underwater	1.3841	0.1389	68.704		<0.001
		Age in months	0.0072	0.0018	14.224		<0.001
	Model 2	Age group			14.627		0.006
		Age group 2	0.0109	0.1969		0.055	0.956
		Age group 3	0.1200	0.2025		0.593	0.553
		Age group 4	0.4832	0.1937		2.495	0.013
		Age group 5	0.6104	0.2121		2.877	0.004
Number of correction trials	Model 3	Stimulus group: Underwater	1.7887	0.1470	88.076		<0.001
		Age in months	0.0067	0.0022	9.584		0.002
	Model 4	Age group			11.181		0.025
		Age group 2	−0.0631	0.2135		−0.295	0.768
		Age group 3	0.3723	0.2155		1.728	0.084
		Age group 4	0.4144	0.2151		1.927	0.054
		Age group 5	0.5741	0.2412		2.383	0.017

Z tests indicate which age groups differ from age group 1 in the respective analysis. Bold numbers indicate significant values at p = ≤0.05