Table 3.

Slopes and intercepts of the squared threshold contrast versus external noise variance functions.

Observer	Percent Correct (%)	Orientation Separation (Δθ)
		±3°		±6°		±15°		±45°
		slope	intercept	slope	intercept	slope	intercept	slope	intercept
CB (r2 = 0.9975)	65	0.88	0.015	0.51	0.006	0.34	0.005	0.15	0.003
	75	1.94	0.032	1.02	0.011	0.55	0.007	0.28	0.006
	85	3.75	0.062	1.81	0.020	0.84	0.011	0.47	0.009
JS (r2 = 0.9928)	65	1.74	0.005	0.79	0.008	0.54	0.003	0.22	0.005
	75	4.48	0.014	1.30	0.012	0.88	0.005	0.32	0.007
	85	10.14	0.032	1.98	0.019	1.34	0.008	0.46	0.010
SJ (r2 = 0.9976)	65	1.31	0.009	0.49	0.005	0.45	0.003	0.22	0.000
	75	2.21	0.016	0.84	0.008	0.71	0.005	0.39	0.001
	85	3.42	0.024	1.31	0.013	1.03	0.007	0.65	0.001
IO (r2 = 0.9999)	65	0.053	0	0.017	0	0.0061	0	0.0051	0
	75	0.146	0	0.044	0	0.0163	0	0.0137	0
	85	0.336	0	0.099	0	0.0366	0	0.0312	0