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. 2012 May 23;20(4-5):391–421. doi: 10.1080/13506285.2012.670143

TABLE 1.

SWIFT parameters for shuffled and normal text reading

Shuffled text Normal text t-test (Welch)
Parameter Symbol Ma SEa Ma SEa p-value Rangeb Equation
Lexical parameters Frequency, intercept α 16.8 1.3 18.7 0.97 .25 1–40
Frequency, slope β 0.28 0.02 0.71 0.03 .000 0–1
Predictability θ 0 1.18 0.16 0–4.6
Global inhibition ppf 24.16 2.36 0.069 0.047 .000 0–30
Visual processing Visual span, constant δ0 6.61 0.44 1.64 0.26 .000 0–10 1, 4
Visual span, dynamic δ1 3.98 0.88 2.15 0.64 .112 0–15 1, 4
Visual span, dynamic—additivec δ1additive 26.45 6.40 2.27 0.29 .004 3
Visual span, preprocessing pspan 15.0 15.0
Word length exponent η 0.3 0.3
Preprocessing factor f 0.609 0.068 0.814 0.059 .04 0.1–1
Global decay ω 0.01 0.01
Transfer across saccades ι 0.91 0.03 0.50 0.08 .001 0.1–1
Eye–mind lag pcd 30.0 30.0
Saccade timing Random timing (ms) tsac 292.5 4.6 221.2 3.8 .000 10–400
Random timing—starting value tsac0 0.8 0.8
Inhibition factor h 0.085 0.056 0.549 0.160 .02 0–5
Target selection weight γ 1.0 1.0
Saccade programs Labile stage (ms) τlab 100.0 100.0
Refixation factor refix 0.7 0.7
Mislocated fixation factor misfac 0.75 0.75
Nonlabile stage (ms) τ0nl 50.0 50.0
Latency modulation κ0 2.5 2.5
Latency modulation κ1 0.3 0.3
Saccade execution (ms) τex 30.0 30.0
a

Means and standard errors over 10 independent runs of the genetic algorithm (for each run using the optimal parameter set from the last 500 generations). Other parameters were fixed for previous model versions or for theoretical reasons, and no standard errors are given for these parameters.

b

Parameter boundaries used in fitting.

c

Parameter was calculated from fitted values.