Table 1. The table shows for each condition and observer the mean (μ) and standard deviation (σ) of the fitted psychometric functions and the log likelihood of the fits (see black curves in Figure 3).

The fourth row for each observer shows the significance level (*: p < 0.1, **: p < 0.01, ***: p < 0.001) and χ² between the separate fits to size- and density-varying trials and for their combined fit. Single stair: separate density and size judgments in blocked density-varying and size-varying trials. Mixed task: interleaved size- and density-varying trials. Numerosity task: numerosity judgment of interleaved density and size trials.

	Single stair			Mixed task			Numerosity task
Obs	Dens		Size	Dens		Size	Dens		Size
1
μ	3.82		2.13	−0.33		0.18	−1.48		−0.86
σ	15.81		9.35	15.3		7.45	14.03		9.19
log(L)	242.66		182.44	225.77		154.30	302.30		255.28
χ2		11.68***			19.52***			7.33***
2
μ	0.16		2.65	2.96		1.90	2.47		1.49
σ	19.17		10.97	22.16		10.89	35.82		13.23
log(L)	257.65		192.77	277.41		202.06	280.38		239.73
χ 2		13.06***			18.08***			30.86***
3
μ	4.30		−0.81	6.18		2.76	4.93		2.90
σ	14.91		5.93	15.32		6.27	12.43		8.95
log(L)	246.69		160.44	243.58		144.33	205.70		178.59
χ 2		40.92***			33.39***			5.93**
4
μ	−2.41		−4.78	0.34		0.46	−2.34		−2.74
σ	14.19		9.52	14.00		9.45	11.41		15.15
log(L)	421.32		354.45	398.21		313.75	387.55		450.80
χ 2		18.89***			11.79***			6.71**