Table 2. Statistical analysis of the overall population response curve (green) of Fig 1.

Right-hand aperture width	2.0 cm	3.0 cm	4.0 cm	5.0 cm	6.0 cm	7.0 cm	8.0 cm
Measured choice probabilities	0.075	0.161	0.312	0.517	0.717	0.857	0.934
Zero bias function choice probabilities	0.070	0.152	0.297	0.5	0.703	0.848	0.930
Standard error (S.E.)	0.011	0.014	0.019	0.021	0.018	0.014	0.010
Z-score (proportion test)	0.430	0.636	0.738	0.800	0.759	0.614	0.423
p-values	0.166	0.239	0.270	0.288	0.276	0.229	0.163

Comparison of the measured choice probabilities with the theoretical values expected from a zero-bias curve, using a proportion test.