Table 1.

Equations used for fitting congruent rate, overall rate, and fraction of congruent fixational saccades. Subscripts 1 and 2 indicate parafoveal-only and parafoveal+peripheral conditions, respectively. f₁(c) and f₂(c), fraction of congruent fixational saccades as a function of parafoveal contrast c. R_o1(c) and R_o2(c), overall rate of fixational saccades. R_c1(c) and R_c2(c), rate of congruent fixational saccades. R_c1,2(c) = R_o1,2(c)f_1,2(c) for each combination of rate and fraction models.

Type of data	DC Model	Same Model	Different Model
Fraction of congruent fixational saccades	f1(c) = b1 f2(c) = b2	$f_1(C)={}_{f}C{}^n/(C^n+{}_f{}^n)+0.25$ f2(c) = f1(c)	$f_1(C)={}_{f1}C{}^n/(C^n+{}_f{}^n)+0.25$ $f_1(C)={}_{f2}C{}^n/(C^n+{}_f{}^n)+0.25$
	2 parameters: (b1, b2)	3 parameters: (f, n, f)	4 parameters: (f1, f2,n,f)
Congruent Rate	Rc1(c) = 1f1(c) Rc2(c) = 2f2(c)	Rc1(c) = Rcm/ (cm + Rm) + Rc2(c) = Ro2(c)f2(c) = Rc1(c)f2(c)/f1(c)	Rc1(c) = R cm/ (cm + Rm) + Rc2(c) = Ro2(c)f2(c) = Rc1(c)f2(c)/f1(c) + f2(c)
Overall Rate	Ro1(c) = 1 Ro2(c) = 2	Ro1 (c) = Rc1(c)/f1(c) Ro2 (c) = Ro1(c)	Ro1 (c) = Rc1(c)/f1(c) Ro2(c) = Ro1(c) +
	2 parameters: (1, 2)	4 parameters: (R, m, R,)	5 parameters: (R, m, R, ,)

DC Fraction model, parameters b₁ and b₂ specify f₁ and f₂, respectively. Same Fraction model, parameters _fn, _f correspond to the gain, exponent, and semi-saturation, respectively, of a Nara-Rushton function (shared for f₁ and f₂). Different Fraction model, _f1, and _f2 correspond to the gain of f₁ and f₂, respectively; n, _f correspond to the exponent, and semi-saturation (shared for f₁ and f₂). DC Rate model, parameters ₁ and ₂ specify the overall rates. Same Rate model and Difference Rate models, parameters _R, m, _R, and correspond to the gain, exponent, semi-saturation, and baseline, respectively, of the Nara-Rushton function that specify one of the congruent rate curves R_c1(c). The other three curves, R_c2(c), (R_o1(c), and R_o2(c), are specified relative to that function. Same Rate model, R_o1(c), = R_o2(c). Different Rate model, R_o1(c) and R_o2(c) differ by a constant.