Table 1.

Individual and mean estimates of threshold (dB SPL), slope (log d^′∕dB) and criterion from the individual fitted psychometric functions. Values of r² show the proportion of variance in the data accounted for by the estimates.

Subject	Noise masker
	Uncertain				Defined
	Threshold	Slope	Criterion	r2	Threshold	Slope	Criterion	r2
S1	33.3	0.7	1.0	0.88	34.6	1.3	0.6	0.90
S2	35.5	0.8	0.6	0.92	32.4	0.8	0.7	0.95
S3	34.9	1.1	1.4	0.94	33.8	1.0	1.1	0.90
S4	34.6	0.9	1.5	0.83	30.0	0.5	1.0	0.98
Mean	34.6	0.9	1.1	0.89	32.7	0.9	0.9	0.93
	Random two-tone masker
S1	47.5	0.4	0.1	0.67	32.2	0.3	0.3	0.57
S2	17.2	0.2	0.6	0.51	5.2	0.2	0.8	0.86
S3	18.3	0.3	0.8	0.77	13.3	0.4	0.6	0.54
S4	30.3	0.2	0.5	0.58	25.3	0.6	0.2	0.76
Mean	28.3	0.3	0.5	0.63	19.0	0.4	0.5	0.68