RePsychLing Kliegl, Kuschela, & Laubrock (2015)- Reduction of Model Complexity

Author

Phillip Alday, Douglas Bates, and Reinhold Kliegl

Published

2024-06-27

1 Background

Kliegl et al. (2015) is a follow-up to Kliegl et al. (2011) (see also script kwdyz11.qmd) from an experiment looking at a variety of effects of visual cueing under four different cue-target relations (CTRs). In this experiment two rectangles are displayed (1) in horizontal orientation , (2) in vertical orientation, (3) in left diagonal orientation, or in (4) right diagonal orientation relative to a central fixation point. Subjects react to the onset of a small or a large visual target occurring at one of the four ends of the two rectangles. The target is cued validly on 70% of trials by a brief flash of the corner of the rectangle at which it appears; it is cued invalidly at the three other locations 10% of the trials each. This implies a latent imbalance in design that is not visible in the repeated-measures ANOVA, but we will show its effect in the random-effect structure and conditional modes.

There are a couple of differences between the first and this follow-up experiment, rendering it more a conceptual than a direct replication. First, the original experiment was carried out at Peking University and this follow-up at Potsdam University. Second, diagonal orientations of rectangles and large target sizes were not part of the design of Kliegl et al. (2011).

We specify three contrasts for the four-level factor CTR that are derived from spatial, object-based, and attractor-like features of attention. They map onto sequential differences between appropriately ordered factor levels. Replicating Kliegl et al. (2011), the attraction effect was not significant as a fixed effect, but yielded a highly reliable variance component (VC; i.e., reliable individual differences in positive and negative attraction effects cancel the fixed effect). Moreover, these individual differences in the attraction effect were negatively correlated with those in the spatial effect.

This comparison is of interest because a few years after the publication of Kliegl et al. (2011), the theoretically critical correlation parameter (CP) between the spatial effect and the attraction effect was determined as the source of a non-singular LMM in that paper. The present study served the purpose to estimate this parameter with a larger sample and a wider variety of experimental conditions.

Here we also include two additional experimental manipulations of target size and orientation of cue rectangle. A similar analysis was reported in the parsimonious mixed-model paper (Bates et al., 2015); it was also used in a paper of GAMMs (Baayen et al., 2017). Data and R scripts of those analyses are also available in R-package RePsychLing.

The analysis is based on log-transformed reaction times lrt, indicated by a boxcox() check of model residuals.

In this vignette we focus on the reduction of model complexity. And we start with a quote:

“Neither the [maximal] nor the [minimal] linear mixed models are appropriate for most repeated measures analysis. Using the [maximal] model is generally wasteful and costly in terms of statiscal power for testing hypotheses. On the other hand, the [minimal] model fails to account for nontrivial correlation among repeated measurements. This results in inflated [T]ype I error rates when non-negligible correlation does in fact exist. We can usually find middle ground, a covariance model that adequately accounts for correlation but is more parsimonious than the [maximal] model. Doing so allows us full control over [T]ype I error rates without needlessly sacrificing power.”

Stroup, W. W. (2012, p. 185). Generalized linear mixed models: Modern concepts, methods and applica?ons. CRC Press, Boca Raton.

2 Packages

Code
using Arrow
using AlgebraOfGraphics
using AlgebraOfGraphics: density
using BoxCox
using CairoMakie
using CategoricalArrays
using Chain
using DataFrameMacros
using DataFrames
using MixedModels
using MixedModelsMakie
using ProgressMeter
using Random
using SMLP2023: dataset
using StatsBase

ProgressMeter.ijulia_behavior(:clear)
CairoMakie.activate!(; type="svg")

3 Read data, compute and plot means

dat = DataFrame(dataset(:kkl15))
describe(dat)
5×7 DataFrame
Row variable mean min median max nmissing eltype
Symbol Union… Any Union… Any Int64 DataType
1 Subj S001 S147 0 String
2 CTR dod val 0 String
3 rt 293.147 150.22 276.594 749.481 0 Float32
4 cardinal cardinal diagonal 0 String
5 size big small 0 String
dat_subj = combine(
  groupby(dat, [:Subj, :CTR]),
  nrow => :n,
  :rt => mean => :rt_m,
  :rt => (c -> mean(log, c)) => :lrt_m,
)
dat_subj.CTR = categorical(dat_subj.CTR, levels=levels(dat.CTR))
describe(dat_subj)
5×7 DataFrame
Row variable mean min median max nmissing eltype
Symbol Union… Any Union… Any Int64 DataType
1 Subj S001 S147 0 String
2 CTR val dod 0 CategoricalValue{String, UInt32}
3 n 156.294 49 64.0 448 0 Int64
4 rt_m 308.223 208.194 304.862 584.71 0 Float32
5 lrt_m 5.6908 5.33226 5.69848 6.36141 0 Float32
Code
boxplot(
  dat_subj.CTR.refs,
  dat_subj.lrt_m;
  orientation=:horizontal,
  show_notch=true,
  axis=(;
    yticks=(
      1:4,
      [
        "valid cue",
        "same obj/diff pos",
        "diff obj/same pos",
        "diff obj/diff pos",
      ]
    )
  ),
  figure=(; resolution=(800, 300)),
)
Figure 1: Comparative boxplots of mean log response time by subject under different conditions

Mean of log reaction times for four cue-target relations. Targets appeared at (a) the cued position (valid) in a rectangle, (b) in the same rectangle cue, but at its other end, (c) on the second rectangle, but at a corresponding horizontal/vertical physical distance, or (d) at the other end of the second rectangle, that is \(\sqrt{2}\) of horizontal/vertical distance diagonally across from the cue, that is also at larger physical distance compared to (c).

We remove the outlier subject and replot, but we model the data points in dat and check whether this subject appears as an outlier in the caterpillar plot of conditional modes.

Code
let dat_subj = filter(r -> r.rt_m < 510, dat_subj)
  boxplot(
    dat_subj.CTR.refs,
    dat_subj.lrt_m;
    orientation=:horizontal,
    show_notch=true,
    axis=(;
      yticks=(
        1:4,
        [
          "valid cue",
          "same obj/diff pos",
          "diff obj/same pos",
          "diff obj/diff pos",
        ]
      )
    ),
    figure=(; resolution=(800, 300)),
  )
end
Figure 2: Comparative boxplots of mean log response time by subject under different conditions without outlier

4 Setup of linear mixed model

4.1 Contrasts

contrasts = Dict(
  :Subj => Grouping(),
  :CTR => SeqDiffCoding(; levels=["val", "sod", "dos", "dod"]),
  :cardinal => EffectsCoding(; levels=["cardinal", "diagonal"]),
  :size => EffectsCoding(; levels=["big", "small"])
)
Dict{Symbol, StatsModels.AbstractContrasts} with 4 entries:
  :CTR      => SeqDiffCoding(["val", "sod", "dos", "dod"])
  :size     => EffectsCoding(nothing, ["big", "small"])
  :Subj     => Grouping()
  :cardinal => EffectsCoding(nothing, ["cardinal", "diagonal"])
m_max_rt = let
  form = @formula rt ~ 1 + CTR * size * cardinal + 
                           (1 + CTR * size * cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 3872    Time: 0:00:06 ( 1.59 ms/it)
  objective:  599297.6610000695
Est. SE z p σ_Subj
(Intercept) 308.4078 5.8365 52.84 <1e-99 0.0000
CTR: sod 23.2685 2.5676 9.06 <1e-18 9.9631
CTR: dos 13.0802 1.5433 8.48 <1e-16 5.0118
CTR: dod 2.7724 2.0921 1.33 0.1851 13.1147
size: small 26.4130 5.8365 4.53 <1e-05 54.0095
cardinal: diagonal 6.6749 1.7890 3.73 0.0002 9.7692
CTR: sod & size: small 8.7924 2.5676 3.42 0.0006 19.8731
CTR: dos & size: small -0.7061 1.5433 -0.46 0.6473 7.2502
CTR: dod & size: small 7.4980 2.0921 3.58 0.0003 8.7387
CTR: sod & cardinal: diagonal 3.6315 1.1022 3.29 0.0010 4.2292
CTR: dos & cardinal: diagonal 1.3344 1.2450 1.07 0.2838 1.7717
CTR: dod & cardinal: diagonal -0.2247 1.3224 -0.17 0.8651 4.0782
size: small & cardinal: diagonal 2.0502 1.7890 1.15 0.2518 12.9327
CTR: sod & size: small & cardinal: diagonal -0.7638 1.1022 -0.69 0.4883 3.7198
CTR: dos & size: small & cardinal: diagonal -0.1556 1.2450 -0.12 0.9005 1.7390
CTR: dod & size: small & cardinal: diagonal 4.1768 1.3224 3.16 0.0016 2.3972
Residual 63.0091
m_cpx_rt = let
  form = @formula rt ~ 1 + CTR * size * cardinal + 
                           (1 + CTR + size + cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 770    Time: 0:00:00 ( 0.25 ms/it)
Est. SE z p σ_Subj
(Intercept) 308.4074 6.0527 50.95 <1e-99 40.4433
CTR: sod 23.2723 2.4739 9.41 <1e-20 21.2925
CTR: dos 13.1099 1.4621 8.97 <1e-18 7.5060
CTR: dod 2.7140 1.9182 1.41 0.1571 13.7125
size: small 26.3865 6.0527 4.36 <1e-04 38.7600
cardinal: diagonal 6.6506 1.7311 3.84 0.0001 15.6567
CTR: sod & size: small 8.7956 2.4739 3.56 0.0004
CTR: dos & size: small -0.7230 1.4621 -0.49 0.6209
CTR: dod & size: small 7.4191 1.9182 3.87 0.0001
CTR: sod & cardinal: diagonal 3.6414 0.9210 3.95 <1e-04
CTR: dos & cardinal: diagonal 1.3276 1.2176 1.09 0.2755
CTR: dod & cardinal: diagonal -0.3142 1.2217 -0.26 0.7970
size: small & cardinal: diagonal 2.0470 1.7311 1.18 0.2370
CTR: sod & size: small & cardinal: diagonal -0.7611 0.9210 -0.83 0.4086
CTR: dos & size: small & cardinal: diagonal -0.1334 1.2176 -0.11 0.9128
CTR: dod & size: small & cardinal: diagonal 4.1115 1.2217 3.37 0.0008
Residual 63.1011

4.2 Box-Cox

bc1 = fit(BoxCoxTransformation, m_max_rt)
bc2 = fit(BoxCoxTransformation, m_cpx_rt)
Minimizing 1191    Time: 0:00:00 ( 0.14 ms/it)
Box-Cox transformation

estimated λ: -0.7062
resultant transformation:

 y^-0.7 - 1
------------
    -0.7
boxcoxplot(bc2; conf_level=0.95)

Clear evidence for skew. Traditionally, we used log transforms for reaction times. even stronger than log. We stay with log for now. Could try 1/sqrt(rt).

5 Maximum LMM

This is the maximum LMM for the design.

m_max = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                           (1 + CTR * size * cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 8282    Time: 0:00:13 ( 1.63 ms/it)
  objective:  -24691.24618930951
Est. SE z p σ_Subj
(Intercept) 5.6911 0.0174 327.65 <1e-99 0.0000
CTR: sod 0.0744 0.0078 9.52 <1e-20 0.0096
CTR: dos 0.0408 0.0047 8.75 <1e-17 0.0135
CTR: dod 0.0018 0.0056 0.31 0.7553 0.0233
size: small 0.0921 0.0174 5.30 <1e-06 0.1607
cardinal: diagonal 0.0205 0.0052 3.91 <1e-04 0.0261
CTR: sod & size: small 0.0244 0.0078 3.12 0.0018 0.0671
CTR: dos & size: small -0.0054 0.0047 -1.15 0.2492 0.0231
CTR: dod & size: small 0.0183 0.0056 3.25 0.0011 0.0320
CTR: sod & cardinal: diagonal 0.0101 0.0032 3.12 0.0018 0.0074
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.24 0.2149 0.0039
CTR: dod & cardinal: diagonal -0.0054 0.0039 -1.39 0.1648 0.0082
size: small & cardinal: diagonal 0.0042 0.0052 0.80 0.4264 0.0395
CTR: sod & size: small & cardinal: diagonal -0.0032 0.0032 -0.98 0.3287 0.0135
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.14 0.8925 0.0033
CTR: dod & size: small & cardinal: diagonal 0.0111 0.0039 2.85 0.0044 0.0082
Residual 0.1902
issingular(m_max)
true
only(MixedModels.PCA(m_max))

Principal components based on correlation matrix
 (Intercept)                                  …    .      .      .      .      .
 CTR: sod                                          .      .      .      .      .
 CTR: dos                                          .      .      .      .      .
 CTR: dod                                          .      .      .      .      .
 size: small                                       .      .      .      .      .
 CTR: sod & size: small                       …    .      .      .      .      .
 CTR: dos & size: small                            .      .      .      .      .
 CTR: dod & size: small                            .      .      .      .      .
 cardinal: diagonal                                .      .      .      .      .
 CTR: sod & cardinal: diagonal                     .      .      .      .      .
 CTR: dos & cardinal: diagonal                …    .      .      .      .      .
 CTR: dod & cardinal: diagonal                    1.0     .      .      .      .
 size: small & cardinal: diagonal                 0.03   1.0     .      .      .
 CTR: sod & size: small & cardinal: diagonal      0.44  -0.02   1.0     .      .
 CTR: dos & size: small & cardinal: diagonal      0.75   0.36   0.1    1.0     .
 CTR: dod & size: small & cardinal: diagonal  …   0.28  -0.05   0.67  -0.13   1.0

Normalized cumulative variances:
[0.3, 0.577, 0.7187, 0.8235, 0.9131, 0.9482, 0.9806, 0.9983, 0.9997, 0.9999, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0]

Component loadings
                                              …    PC13    PC14    PC15    PC16
 (Intercept)                                     -0.0    -0.0     0.0    -1.0
 CTR: sod                                        -0.03    0.07   -0.02    0.0
 CTR: dos                                         0.41    0.2     0.12   -0.0
 CTR: dod                                        -0.02   -0.25    0.29    0.0
 size: small                                  …   0.06   -0.26   -0.47   -0.0
 CTR: sod & size: small                           0.15    0.49   -0.11   -0.0
 CTR: dos & size: small                           0.41    0.36    0.24   -0.0
 CTR: dod & size: small                          -0.16   -0.35    0.47    0.0
 cardinal: diagonal                              -0.3     0.16    0.1     0.0
 CTR: sod & cardinal: diagonal                …   0.11   -0.06    0.04   -0.0
 CTR: dos & cardinal: diagonal                   -0.04   -0.33   -0.17    0.0
 CTR: dod & cardinal: diagonal                   -0.32    0.11   -0.05    0.0
 size: small & cardinal: diagonal                -0.37    0.26    0.11   -0.0
 CTR: sod & size: small & cardinal: diagonal      0.21   -0.14    0.16   -0.0
 CTR: dos & size: small & cardinal: diagonal  …   0.35   -0.2    -0.4     0.0
 CTR: dod & size: small & cardinal: diagonal     -0.32    0.22   -0.39    0.0
VarCorr(m_max)
Column Variance Std.Dev Corr.
Subj (Intercept) 0.00000000 0.00000000
CTR: sod 0.00009280 0.00963318 +NaN
CTR: dos 0.00018297 0.01352646 +NaN -0.01
CTR: dod 0.00054215 0.02328402 +NaN +0.51 -0.35
size: small 0.02583099 0.16072022 +NaN +0.90 +0.19 +0.67
CTR: sod & size: small 0.00449651 0.06705605 +NaN +0.10 +0.32 +0.55 +0.50
CTR: dos & size: small 0.00053188 0.02306260 +NaN +0.26 -0.74 +0.66 +0.19 -0.09
CTR: dod & size: small 0.00102251 0.03197673 +NaN +0.40 +0.45 +0.49 +0.68 +0.70 +0.15
cardinal: diagonal 0.00068321 0.02613836 +NaN +0.14 -0.55 +0.06 -0.07 -0.23 +0.14 -0.49
CTR: sod & cardinal: diagonal 0.00005543 0.00744533 +NaN +0.25 -0.30 -0.25 -0.01 -0.43 +0.05 -0.32 +0.25
CTR: dos & cardinal: diagonal 0.00001502 0.00387533 +NaN -0.79 +0.30 -0.18 -0.48 +0.40 -0.31 +0.02 -0.34 -0.42
CTR: dod & cardinal: diagonal 0.00006782 0.00823543 +NaN +0.35 -0.55 +0.34 +0.14 -0.36 +0.83 +0.17 +0.02 +0.24 -0.59
size: small & cardinal: diagonal 0.00156110 0.03951070 +NaN -0.02 +0.06 +0.09 +0.07 -0.06 +0.24 +0.09 -0.49 +0.10 +0.29 +0.03
CTR: sod & size: small & cardinal: diagonal 0.00018092 0.01345048 +NaN +0.28 -0.08 +0.15 +0.26 +0.04 +0.28 +0.35 -0.21 -0.13 -0.33 +0.44 -0.02
CTR: dos & size: small & cardinal: diagonal 0.00001090 0.00330194 +NaN +0.09 -0.75 +0.38 -0.06 -0.36 +0.91 -0.10 +0.26 +0.20 -0.23 +0.75 +0.36 +0.10
CTR: dod & size: small & cardinal: diagonal 0.00006649 0.00815442 +NaN +0.23 +0.34 +0.37 +0.47 +0.55 +0.17 +0.87 -0.56 -0.43 -0.01 +0.28 -0.05 +0.67 -0.13
Residual 0.03617587 0.19019955

6 Reduction strategy 1

6.1 Zero-correlation parameter LMM (1)

Force CPs to zero.

m_zcp1 = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                   zerocorr(1 + CTR * size * cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 637    Time: 0:00:00 ( 0.32 ms/it)
  objective:  -24588.607469898558
Est. SE z p σ_Subj
(Intercept) 5.6910 0.0173 329.51 <1e-99 0.0151
CTR: sod 0.0744 0.0077 9.66 <1e-21 0.0109
CTR: dos 0.0409 0.0045 9.09 <1e-19 0.0240
CTR: dod 0.0015 0.0053 0.29 0.7749 0.0299
size: small 0.0921 0.0173 5.33 <1e-07 0.1591
cardinal: diagonal 0.0204 0.0052 3.92 <1e-04 0.0312
CTR: sod & size: small 0.0244 0.0077 3.17 0.0015 0.0657
CTR: dos & size: small -0.0053 0.0045 -1.19 0.2344 0.0010
CTR: dod & size: small 0.0181 0.0053 3.39 0.0007 0.0196
CTR: sod & cardinal: diagonal 0.0101 0.0033 3.03 0.0025 0.0172
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.26 0.2092 0.0000
CTR: dod & cardinal: diagonal -0.0055 0.0037 -1.49 0.1358 0.0033
size: small & cardinal: diagonal 0.0041 0.0052 0.79 0.4291 0.0354
CTR: sod & size: small & cardinal: diagonal -0.0032 0.0033 -0.95 0.3427 0.0008
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.13 0.8945 0.0000
CTR: dod & size: small & cardinal: diagonal 0.0109 0.0037 2.94 0.0033 0.0010
Residual 0.1903
issingular(m_zcp1)
true
only(MixedModels.PCA(m_zcp1))

Principal components based on correlation matrix
 (Intercept)                                  …  .    .    .    .    .    .    .
 CTR: sod                                        .    .    .    .    .    .    .
 CTR: dos                                        .    .    .    .    .    .    .
 CTR: dod                                        .    .    .    .    .    .    .
 size: small                                     .    .    .    .    .    .    .
 CTR: sod & size: small                       …  .    .    .    .    .    .    .
 CTR: dos & size: small                          .    .    .    .    .    .    .
 CTR: dod & size: small                          .    .    .    .    .    .    .
 cardinal: diagonal                              .    .    .    .    .    .    .
 CTR: sod & cardinal: diagonal                   1.0  .    .    .    .    .    .
 CTR: dos & cardinal: diagonal                …  0.0  0.0  .    .    .    .    .
 CTR: dod & cardinal: diagonal                   0.0  0.0  1.0  .    .    .    .
 size: small & cardinal: diagonal                0.0  0.0  0.0  1.0  .    .    .
 CTR: sod & size: small & cardinal: diagonal     0.0  0.0  0.0  0.0  1.0  .    .
 CTR: dos & size: small & cardinal: diagonal     0.0  0.0  0.0  0.0  0.0  0.0  .
 CTR: dod & size: small & cardinal: diagonal  …  0.0  0.0  0.0  0.0  0.0  0.0  1.0

Normalized cumulative variances:
[0.0714, 0.1429, 0.2143, 0.2857, 0.3571, 0.4286, 0.5, 0.5714, 0.6429, 0.7143, 0.7857, 0.8571, 0.9286, 1.0, 1.0, 1.0]

Component loadings
                                              …   PC13   PC14     PC15     PC16
 (Intercept)                                     0.0    0.0      0.0      0.0
 CTR: sod                                        0.0    0.0      0.0      0.0
 CTR: dos                                        0.0    0.0      0.0      0.0
 CTR: dod                                        0.0    0.0      0.0      0.0
 size: small                                  …  0.0    0.0      0.0      0.0
 CTR: sod & size: small                          0.0    0.0      0.0      0.0
 CTR: dos & size: small                          0.0    0.0      0.0      0.0
 CTR: dod & size: small                          1.0    0.0      0.0      0.0
 cardinal: diagonal                              0.0    1.0      0.0      0.0
 CTR: sod & cardinal: diagonal                …  0.0    0.0      0.0      0.0
 CTR: dos & cardinal: diagonal                   0.0    0.0    NaN        0.0
 CTR: dod & cardinal: diagonal                   0.0    0.0      0.0      0.0
 size: small & cardinal: diagonal                0.0    0.0      0.0      0.0
 CTR: sod & size: small & cardinal: diagonal     0.0    0.0      0.0      0.0
 CTR: dos & size: small & cardinal: diagonal  …  0.0    0.0      0.0    NaN
 CTR: dod & size: small & cardinal: diagonal     0.0    0.0      0.0      0.0
VarCorr(m_zcp1)
Column Variance Std.Dev Corr.
Subj (Intercept) 0.000228119 0.015103595
CTR: sod 0.000118184 0.010871228 .
CTR: dos 0.000577145 0.024023842 . .
CTR: dod 0.000894364 0.029905924 . . .
size: small 0.025310609 0.159093081 . . . .
CTR: sod & size: small 0.004316747 0.065701959 . . . . .
CTR: dos & size: small 0.000000926 0.000962365 . . . . . .
CTR: dod & size: small 0.000383055 0.019571794 . . . . . . .
cardinal: diagonal 0.000972318 0.031182012 . . . . . . . .
CTR: sod & cardinal: diagonal 0.000294448 0.017159499 . . . . . . . . .
CTR: dos & cardinal: diagonal 0.000000000 0.000000000 . . . . . . . . . .
CTR: dod & cardinal: diagonal 0.000010975 0.003312812 . . . . . . . . . . .
size: small & cardinal: diagonal 0.001254094 0.035413184 . . . . . . . . . . . .
CTR: sod & size: small & cardinal: diagonal 0.000000719 0.000847671 . . . . . . . . . . . . .
CTR: dos & size: small & cardinal: diagonal 0.000000000 0.000000000 . . . . . . . . . . . . . .
CTR: dod & size: small & cardinal: diagonal 0.000001038 0.001019064 . . . . . . . . . . . . . . .
Residual 0.036196631 0.190254123

6.2 Reduced zcp LMM

Take out VC for interactions.

m_zcp1_rdc = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                   zerocorr(1 + CTR + size + cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Est. SE z p σ_Subj
(Intercept) 5.6911 0.0173 329.28 <1e-99 0.1569
CTR: sod 0.0745 0.0077 9.66 <1e-21 0.0666
CTR: dos 0.0409 0.0045 9.09 <1e-19 0.0240
CTR: dod 0.0015 0.0053 0.29 0.7751 0.0357
size: small 0.0920 0.0173 5.33 <1e-06 0.0312
cardinal: diagonal 0.0204 0.0053 3.88 0.0001 0.0476
CTR: sod & size: small 0.0244 0.0077 3.17 0.0015
CTR: dos & size: small -0.0054 0.0045 -1.20 0.2317
CTR: dod & size: small 0.0181 0.0053 3.39 0.0007
CTR: sod & cardinal: diagonal 0.0101 0.0028 3.64 0.0003
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.25 0.2125
CTR: dod & cardinal: diagonal -0.0056 0.0037 -1.51 0.1317
size: small & cardinal: diagonal 0.0042 0.0053 0.79 0.4286
CTR: sod & size: small & cardinal: diagonal -0.0031 0.0028 -1.12 0.2610
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.12 0.9023
CTR: dod & size: small & cardinal: diagonal 0.0109 0.0037 2.95 0.0032
Residual 0.1904
issingular(m_zcp1_rdc)
false
only(MixedModels.PCA(m_zcp1_rdc))

Principal components based on correlation matrix
 (Intercept)         1.0  .    .    .    .    .
 CTR: sod            0.0  1.0  .    .    .    .
 CTR: dos            0.0  0.0  1.0  .    .    .
 CTR: dod            0.0  0.0  0.0  1.0  .    .
 size: small         0.0  0.0  0.0  0.0  1.0  .
 cardinal: diagonal  0.0  0.0  0.0  0.0  0.0  1.0

Normalized cumulative variances:
[0.1667, 0.3333, 0.5, 0.6667, 0.8333, 1.0]

Component loadings
                      PC1   PC2   PC3   PC4   PC5   PC6
 (Intercept)         1.0   0.0   0.0   0.0   0.0   0.0
 CTR: sod            0.0   1.0   0.0   0.0   0.0   0.0
 CTR: dos            0.0   0.0   1.0   0.0   0.0   0.0
 CTR: dod            0.0   0.0   0.0   1.0   0.0   0.0
 size: small         0.0   0.0   0.0   0.0   1.0   0.0
 cardinal: diagonal  0.0   0.0   0.0   0.0   0.0   1.0
VarCorr(m_zcp1_rdc)
Column Variance Std.Dev Corr.
Subj (Intercept) 0.0246022 0.1568508
CTR: sod 0.0044408 0.0666395 .
CTR: dos 0.0005763 0.0240065 . .
CTR: dod 0.0012752 0.0357098 . . .
size: small 0.0009731 0.0311946 . . . .
cardinal: diagonal 0.0022679 0.0476222 . . . . .
Residual 0.0362601 0.1904207

6.3 Model comparison 1

Let’s compare the three models.

gof_summary = let
  nms = [:m_zcp1_rdc, :m_zcp1, :m_max]
  mods = eval.(nms)
  lrt = MixedModels.likelihoodratiotest(m_zcp1_rdc, m_zcp1, m_max)
  DataFrame(;
    name = nms, 
    dof=dof.(mods),
    deviance=round.(deviance.(mods), digits=0),
    AIC=round.(aic.(mods),digits=0),
    AICc=round.(aicc.(mods),digits=0),
     BIC=round.(bic.(mods),digits=0),
    χ²=vcat(:., round.(lrt.tests.deviancediff, digits=0)),
    χ²_dof=vcat(:., round.(lrt.tests.dofdiff, digits=0)),
    pvalue=vcat(:., round.(lrt.tests.pvalues, digits=3))
  )
end
3×9 DataFrame
Row name dof deviance AIC AICc BIC χ² χ²_dof pvalue
Symbol Int64 Float64 Float64 Float64 Float64 Any Any Any
1 m_zcp1_rdc 23 -24558.0 -24512.0 -24512.0 -24308.0 . . .
2 m_zcp1 33 -24589.0 -24523.0 -24523.0 -24229.0 30.0 10.0 0.001
3 m_max 153 -24691.0 -24385.0 -24384.0 -23025.0 103.0 120.0 0.872

6.4 Parsimonious LMM (1)

Extend zcp-reduced LMM with CPs

m_prm1 = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                           (1 + CTR + size + cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 801    Time: 0:00:00 ( 0.18 ms/it)
Est. SE z p σ_Subj
(Intercept) 5.6911 0.0176 323.61 <1e-99 0.1181
CTR: sod 0.0745 0.0076 9.75 <1e-21 0.0660
CTR: dos 0.0408 0.0043 9.42 <1e-20 0.0213
CTR: dod 0.0017 0.0051 0.34 0.7374 0.0326
size: small 0.0921 0.0176 5.23 <1e-06 0.1119
cardinal: diagonal 0.0204 0.0053 3.88 0.0001 0.0476
CTR: sod & size: small 0.0244 0.0076 3.19 0.0014
CTR: dos & size: small -0.0054 0.0043 -1.24 0.2156
CTR: dod & size: small 0.0181 0.0051 3.55 0.0004
CTR: sod & cardinal: diagonal 0.0101 0.0028 3.64 0.0003
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.25 0.2118
CTR: dod & cardinal: diagonal -0.0056 0.0037 -1.51 0.1301
size: small & cardinal: diagonal 0.0042 0.0053 0.79 0.4272
CTR: sod & size: small & cardinal: diagonal -0.0031 0.0028 -1.13 0.2597
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.13 0.8997
CTR: dod & size: small & cardinal: diagonal 0.0110 0.0037 2.98 0.0029
Residual 0.1904
issingular(m_prm1)
false
only(MixedModels.PCA(m_prm1))

Principal components based on correlation matrix
 (Intercept)          1.0     .      .      .      .      .
 CTR: sod             0.64   1.0     .      .      .      .
 CTR: dos             0.16  -0.08   1.0     .      .      .
 CTR: dod             0.79   0.6    0.28   1.0     .      .
 size: small         -0.42  -0.16  -0.12  -0.03   1.0     .
 cardinal: diagonal   0.05  -0.05  -0.02   0.05   0.08   1.0

Normalized cumulative variances:
[0.414, 0.5967, 0.772, 0.926, 0.9822, 1.0]

Component loadings
                       PC1    PC2    PC3    PC4    PC5    PC6
 (Intercept)         -0.6    0.0    0.03   0.12  -0.37  -0.7
 CTR: sod            -0.5   -0.26   0.31  -0.11   0.76   0.02
 CTR: dos            -0.16   0.52  -0.72  -0.23   0.34  -0.11
 CTR: dod            -0.55  -0.18  -0.2   -0.27  -0.4    0.63
 size: small          0.25  -0.59  -0.23  -0.66  -0.03  -0.32
 cardinal: diagonal  -0.0   -0.53  -0.54   0.64   0.12   0.03
VarCorr(m_prm1)
Column Variance Std.Dev Corr.
Subj (Intercept) 0.0139568 0.1181388
CTR: sod 0.0043556 0.0659971 +0.64
CTR: dos 0.0004536 0.0212981 +0.16 -0.08
CTR: dod 0.0010640 0.0326186 +0.79 +0.60 +0.28
size: small 0.0125269 0.1119239 -0.42 -0.16 -0.12 -0.03
cardinal: diagonal 0.0022690 0.0476336 +0.05 -0.05 -0.02 +0.05 +0.08
Residual 0.0362661 0.1904365

We note that the critical correlation parameter between spatial (sod) and attraction (dod) is now estimated at .60 – not that close to the 1.0 boundary that caused singularity in Kliegl et al. (2011).

6.5 Model comparison 2

gof_summary = let
  nms = [:m_zcp1_rdc, :m_prm1, :m_max]
  mods = eval.(nms)
  lrt = MixedModels.likelihoodratiotest(m_prm1, m_zcp1, m_max)
  DataFrame(;
    name = nms, 
    dof=dof.(mods),
    deviance=round.(deviance.(mods), digits=0),
    AIC=round.(aic.(mods),digits=0),
    AICc=round.(aicc.(mods),digits=0),
     BIC=round.(bic.(mods),digits=0),
    χ²=vcat(:., round.(lrt.tests.deviancediff, digits=0)),
    χ²_dof=vcat(:., round.(lrt.tests.dofdiff, digits=0)),
    pvalue=vcat(:., round.(lrt.tests.pvalues, digits=3))
  )
end
3×9 DataFrame
Row name dof deviance AIC AICc BIC χ² χ²_dof pvalue
Symbol Int64 Float64 Float64 Float64 Float64 Any Any Any
1 m_zcp1_rdc 23 -24558.0 -24512.0 -24512.0 -24308.0 . . .
2 m_prm1 38 -24615.0 -24539.0 -24539.0 -24201.0 27.0 5.0 0.0
3 m_max 153 -24691.0 -24385.0 -24384.0 -23025.0 76.0 115.0 0.998

7 Reduction strategy 2

7.1 Complex LMM

Take out interaction VCs.

m_cpx = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                           (1 + CTR + size + cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Minimizing 801    Time: 0:00:00 ( 0.19 ms/it)
Est. SE z p σ_Subj
(Intercept) 5.6911 0.0176 323.61 <1e-99 0.1181
CTR: sod 0.0745 0.0076 9.75 <1e-21 0.0660
CTR: dos 0.0408 0.0043 9.42 <1e-20 0.0213
CTR: dod 0.0017 0.0051 0.34 0.7374 0.0326
size: small 0.0921 0.0176 5.23 <1e-06 0.1119
cardinal: diagonal 0.0204 0.0053 3.88 0.0001 0.0476
CTR: sod & size: small 0.0244 0.0076 3.19 0.0014
CTR: dos & size: small -0.0054 0.0043 -1.24 0.2156
CTR: dod & size: small 0.0181 0.0051 3.55 0.0004
CTR: sod & cardinal: diagonal 0.0101 0.0028 3.64 0.0003
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.25 0.2118
CTR: dod & cardinal: diagonal -0.0056 0.0037 -1.51 0.1301
size: small & cardinal: diagonal 0.0042 0.0053 0.79 0.4272
CTR: sod & size: small & cardinal: diagonal -0.0031 0.0028 -1.13 0.2597
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.13 0.8997
CTR: dod & size: small & cardinal: diagonal 0.0110 0.0037 2.98 0.0029
Residual 0.1904

7.2 Zero-correlation parameter LMM (2)

Take out interaction VCs.

m_zcp2 = let
  form = @formula log(rt) ~ 1 + CTR * size * cardinal + 
                   zerocorr(1 + CTR + size + cardinal | Subj)
  fit(MixedModel, form, dat; contrasts)
end
Est. SE z p σ_Subj
(Intercept) 5.6911 0.0173 329.28 <1e-99 0.1569
CTR: sod 0.0745 0.0077 9.66 <1e-21 0.0666
CTR: dos 0.0409 0.0045 9.09 <1e-19 0.0240
CTR: dod 0.0015 0.0053 0.29 0.7751 0.0357
size: small 0.0920 0.0173 5.33 <1e-06 0.0312
cardinal: diagonal 0.0204 0.0053 3.88 0.0001 0.0476
CTR: sod & size: small 0.0244 0.0077 3.17 0.0015
CTR: dos & size: small -0.0054 0.0045 -1.20 0.2317
CTR: dod & size: small 0.0181 0.0053 3.39 0.0007
CTR: sod & cardinal: diagonal 0.0101 0.0028 3.64 0.0003
CTR: dos & cardinal: diagonal 0.0046 0.0037 1.25 0.2125
CTR: dod & cardinal: diagonal -0.0056 0.0037 -1.51 0.1317
size: small & cardinal: diagonal 0.0042 0.0053 0.79 0.4286
CTR: sod & size: small & cardinal: diagonal -0.0031 0.0028 -1.12 0.2610
CTR: dos & size: small & cardinal: diagonal -0.0005 0.0037 -0.12 0.9023
CTR: dod & size: small & cardinal: diagonal 0.0109 0.0037 2.95 0.0032
Residual 0.1904

7.3 Model comparison 3

gof_summary = let
  nms = [:m_zcp2, :m_cpx, :m_max]
  mods = eval.(nms)
  lrt = MixedModels.likelihoodratiotest(m_zcp2, m_cpx, m_max)
  DataFrame(;
    name = nms, 
    dof=dof.(mods),
    deviance=round.(deviance.(mods), digits=0),
    AIC=round.(aic.(mods),digits=0),
    AICc=round.(aicc.(mods),digits=0),
     BIC=round.(bic.(mods),digits=0),
    χ²=vcat(:., round.(lrt.tests.deviancediff, digits=0)),
    χ²_dof=vcat(:., round.(lrt.tests.dofdiff, digits=0)),
    pvalue=vcat(:., round.(lrt.tests.pvalues, digits=3))
  )
end
3×9 DataFrame
Row name dof deviance AIC AICc BIC χ² χ²_dof pvalue
Symbol Int64 Float64 Float64 Float64 Float64 Any Any Any
1 m_zcp2 23 -24558.0 -24512.0 -24512.0 -24308.0 . . .
2 m_cpx 38 -24615.0 -24539.0 -24539.0 -24201.0 57.0 15.0 0.0
3 m_max 153 -24691.0 -24385.0 -24384.0 -23025.0 76.0 115.0 0.998

8 Check LMM for untransformed reaction times

We see the model is singular.

issingular(m_cpx_rt)
false
MixedModels.PCA(m_cpx_rt)
(Subj = 
Principal components based on correlation matrix
 (Intercept)          1.0     .      .      .      .     .
 CTR: sod             0.85   1.0     .      .      .     .
 CTR: dos             0.56   0.19   1.0     .      .     .
 CTR: dod             0.69   0.54   0.3    1.0     .     .
 size: small         -0.45  -0.23  -0.2   -0.13   1.0    .
 cardinal: diagonal  -0.07  -0.05  -0.08   0.13   0.2   1.0

Normalized cumulative variances:
[0.465, 0.6637, 0.8016, 0.9245, 0.9964, 1.0]

Component loadings
                       PC1    PC2    PC3    PC4    PC5    PC6
 (Intercept)         -0.59  -0.01  -0.02  -0.01  -0.18  -0.79
 CTR: sod            -0.49  -0.12  -0.43  -0.22  -0.51   0.5
 CTR: dos            -0.35   0.13   0.87  -0.05  -0.15   0.27
 CTR: dod            -0.45  -0.36  -0.05  -0.14   0.79   0.17
 size: small          0.29  -0.5    0.17  -0.77  -0.15  -0.17
 cardinal: diagonal   0.05  -0.77   0.12   0.59  -0.21   0.01,)

9 Other checks

m_prm1.θ
m_prm1.lowerbd
m_prm1.λ
1-element Vector{LinearAlgebra.LowerTriangular{Float64, Matrix{Float64}}}:
 [0.6203576608179638 0.0 … 0.0 0.0; 0.22119994699720608 0.26678153140929256 … 0.0 0.0; … ; -0.24965193868875257 0.087476294698932 … 0.4357585158840971 0.0; 0.011471533099315563 -0.0255708216618361 … 0.02800749689407972 0.2461637872603555]

10 Diagnostic plots of LMM residuals

Do model residuals meet LMM assumptions? Classic plots are

  • Residual over fitted
  • Quantiles of model residuals over theoretical quantiles of normal distribution

10.1 Residual-over-fitted plot

The slant in residuals show a lower and upper boundary of reaction times, that is we have have too few short and too few long residuals. Not ideal, but at least width of the residual band looks similar across the fitted values, that is there is no evidence for heteroskedasticity.

Code
CairoMakie.activate!(; type="png")
scatter(fitted(m_prm1), residuals(m_prm1); alpha=0.3)
Figure 3: Residuals versus fitted values for model m1

With many observations the scatterplot is not that informative. Contour plots or heatmaps may be an alternative.

Code
set_aog_theme!()
draw(
  data((; f=fitted(m_prm1), r=residuals(m_prm1))) *
  mapping(
    :f => "Fitted values from m1", :r => "Residuals from m1"
  ) *
  density();
)
Figure 4: Heatmap of residuals versus fitted values for model m1

10.2 Q-Q plot

The plot of quantiles of model residuals over corresponding quantiles of the normal distribution should yield a straight line along the main diagonal.

Code
CairoMakie.activate!(; type="png")
qqnorm(
  residuals(m_prm1);
  qqline=:none,
  axis=(;
    xlabel="Standard normal quantiles",
    ylabel="Quantiles of the residuals from model m1",
  ),
)
Figure 5: Quantile-quantile plot of the residuals for model m1 versus a standard normal

10.3 Observed and theoretical normal distribution

******We****** can see this in this plot. Overall, it does not look too bad.

Code
CairoMakie.activate!(; type="svg")
let
  n = nrow(dat)
  dat_rz = (;
    value=vcat(residuals(m_prm1) ./ std(residuals(m_prm1)), randn(n)),
    curve=repeat(["residual", "normal"]; inner=n),
  )
  draw(
    data(dat_rz) *
    mapping(:value; color=:curve) *
    density(; bandwidth=0.1);
  )
end
Figure 6: Kernel density plot of the standardized residuals for model m1 versus a standard normal

11 Conditional modes

11.1 Caterpillar plot

Code
cm1 = only(ranefinfo(m_prm1))
caterpillar!(Figure(; resolution=(800, 1200)), cm1; orderby=2)
Figure 7: Prediction intervals of the subject random effects in model m1

11.2 Shrinkage plot

11.2.1 Log-transformed reaction times (LMM m_prm1)

Code
shrinkageplot!(Figure(; resolution=(1000, 1200)), m_prm1)
Figure 8: Shrinkage plots of the subject random effects in model m1L

12 Parametric bootstrap

Here we

  • generate a bootstrap sample
  • compute shortest covergage intervals for the LMM parameters
  • plot densities of bootstrapped parameter estimates for residual, fixed effects, variance components, and correlation parameters

12.1 Generate a bootstrap sample

We generate 2500 samples for the 15 model parameters (4 fixed effect, 7 VCs, 15 CPs, and 1 residual).

samp = parametricbootstrap(MersenneTwister(1234321), 2500, m_prm1;
                           optsum_overrides=(; ftol_rel=1e-8));
tbl = samp.tbl
Table with 60 columns and 2500 rows:
      obj       β01      β02        β03        β04           β05        ⋯
    ┌────────────────────────────────────────────────────────────────────
 1  │ -25123.8  5.68038  0.068683   0.039261   -0.00165125   0.0793335  ⋯
 2  │ -24465.9  5.66021  0.0667158  0.0418969  -0.00305185   0.100958   ⋯
 3  │ -24446.4  5.6924   0.0778707  0.0369443  0.00797653    0.100114   ⋯
 4  │ -24617.7  5.69562  0.0766171  0.0463011  -0.00297233   0.0639383  ⋯
 5  │ -25167.8  5.68415  0.0684032  0.0385817  0.00248626    0.118136   ⋯
 6  │ -24727.8  5.69527  0.0843717  0.0442493  0.00193816    0.0936532  ⋯
 7  │ -24512.0  5.67742  0.0707211  0.0418414  -0.00641572   0.076351   ⋯
 8  │ -24798.9  5.69362  0.0765456  0.0458011  0.00328823    0.084062   ⋯
 9  │ -24392.5  5.68477  0.0818642  0.0496969  -0.000832281  0.0977178  ⋯
 10 │ -24585.7  5.68801  0.0796325  0.0344963  0.00629559    0.081441   ⋯
 11 │ -25078.8  5.66697  0.0663796  0.0445354  -0.000736944  0.0943102  ⋯
 12 │ -24348.5  5.67785  0.0698993  0.0446523  -0.000859312  0.102561   ⋯
 13 │ -24973.2  5.68851  0.0732837  0.0421743  -0.00279674   0.0830709  ⋯
 14 │ -24617.9  5.70183  0.07733    0.0433379  -0.00455447   0.0694739  ⋯
 15 │ -24775.8  5.68347  0.0825422  0.0371819  0.00388279    0.0889206  ⋯
 16 │ -24628.0  5.69649  0.0718965  0.0408693  0.000221452   0.0878074  ⋯
 17 │ -24397.7  5.70743  0.0966594  0.0363991  0.00133149    0.087301   ⋯
 18 │ -24836.3  5.73132  0.0753929  0.0424585  0.00735246    0.0482915  ⋯
 19 │ -24806.7  5.68484  0.0744908  0.0369567  0.0060191     0.0529119  ⋯
 20 │ -24234.2  5.6857   0.0691212  0.0481745  -6.76522e-5   0.0718787  ⋯
 21 │ -24927.4  5.67965  0.066628   0.0441619  0.000997131   0.0939013  ⋯
 22 │ -24044.7  5.68194  0.0675943  0.0364103  0.0108015     0.096463   ⋯
 23 │ -24804.0  5.72333  0.0826845  0.0393307  0.00877465    0.0955252  ⋯
 ⋮  │    ⋮         ⋮         ⋮          ⋮           ⋮            ⋮      ⋱

12.2 Shortest coverage interval

confint(samp)
DictTable with 2 columns and 38 rows:
 par   lower        upper
 ────┬────────────────────────
 β01 │ 5.65966      5.72791
 β02 │ 0.0602683    0.0902347
 β03 │ 0.0326438    0.0490006
 β04 │ -0.00832038  0.0114628
 β05 │ 0.0585181    0.124489
 β06 │ 0.00932821   0.030229
 β07 │ 0.00994937   0.0391542
 β08 │ -0.0138358   0.00317468
 β09 │ 0.00770406   0.0274789
 β10 │ 0.00485596   0.0157058
 β11 │ -0.00249685  0.0117935
 β12 │ -0.0124823   0.00202088
 β13 │ -0.00582681  0.0137215
 β14 │ -0.00828443  0.00227533
 β15 │ -0.00842329  0.00599236
 β16 │ 0.00369609   0.0179879
 ρ01 │ 0.380561     1.0
 ρ02 │ -0.342485    0.999999
 ρ03 │ -0.685044    0.682981
 ρ04 │ 0.466487     0.989877
 ρ05 │ 0.330399     0.883748
 ρ06 │ -0.273379    0.932581
 ρ07 │ -0.729693    -0.0549567
  ⋮  │      ⋮           ⋮

We can also visualize the shortest coverage intervals for fixed effects with the ridgeplot() command:

Code
ridgeplot(samp; show_intercept=false)
Figure 9: Ridge plot of fixed-effects bootstrap samples from model m1L

12.3 Comparative density plots of bootstrapped parameter estimates

12.3.1 Residual

Code
draw(
  data(tbl) *
  mapping(:σ => "Residual") *
  density();
  figure=(; resolution=(800, 400)),
)
Figure 10: Kernel density estimate from bootstrap samples of the residual standard deviation for model m_prm1

12.3.2 Fixed effects and associated variance components (w/o GM)

The shortest coverage interval for the GM ranges from x to x ms and the associate variance component from .x to .x. To keep the plot range small we do not include their densities here.

Code
rn = renamer([
  "(Intercept)" => "GM",
  "CTR: sod" => "spatial effect",
  "CTR: dos" => "object effect",
  "CTR: dod" => "attraction effect",
  "(Intercept), CTR: sod" => "GM, spatial",
  "(Intercept), CTR: dos" => "GM, object",
  "CTR: sod, CTR: dos" => "spatial, object",
  "(Intercept), CTR: dod" => "GM, attraction",
  "CTR: sod, CTR: dod" => "spatial, attraction",
  "CTR: dos, CTR: dod" => "object, attraction",
])
draw(
  data(tbl) *
  mapping(
    [:β02, :β03, :β04] .=> "Experimental effect size [ms]";
    color=dims(1) => 
    renamer(["spatial effect", "object effect", "attraction effect"]) =>
    "Experimental effects",
  ) *
  density();
  figure=(; resolution=(800, 350)),
)
Figure 11: Kernel density estimate from bootstrap samples of the fixed effects for model m_prm1

The densitiies correspond nicely with the shortest coverage intervals.

Code
draw(
  data(tbl) *
  mapping(
    [:σ2, :σ3, :σ4] .=> "Standard deviations [ms]";
    color=dims(1) =>
    renamer(["spatial effect", "object effect", "attraction effect"]) =>
    "Variance components",
  ) *
  density();
  figure=(; resolution=(800, 350)),
)
Figure 12: Kernel density estimate from bootstrap samples of the standard deviations for model m1L (excluding Grand Mean)

The VC are all very nicely defined.

12.3.3 Correlation parameters (CPs)

Code
draw(
  data(tbl) *
  mapping(
    [:ρ01, :ρ02, :ρ03, :ρ04, :ρ05, :ρ06] .=> "Correlation";
    color=dims(1) =>
    renamer(["GM, spatial", "GM, object", "spatial, object",
    "GM, attraction", "spatial, attraction", "object, attraction"]) =>
    "Correlation parameters",
  ) *
  density();
  figure=(; resolution=(800, 350)),
)
Figure 13: Kernel density estimate from bootstrap samples of the standard deviations for model m1L

Three CPs stand out positively, the correlation between GM and the spatial effect, GM and attraction effect, and the correlation between spatial and attraction effects. The second CP was positive, but not significant in the first study. The third CP replicates a CP that was judged questionable in script kwdyz11.jl.

The three remaining CPs are not well defined for log-transformed reaction times; they only fit noise and should be removed. It is also possible that fitting the complex experimental design (including target size and rectangle orientation) will lead to more acceptable estimates. The corresponding plot based on LMM m1_rt for raw reaction times still shows them with very wide distributions, but acceptable.

13 References

Baayen, H., Vasishth, S., Kliegl, R., & Bates, D. (2017). The cave of shadows: Addressing the human factor with generalized additive mixed models. Journal of Memory and Language, 94, 206–234. https://doi.org/10.1016/j.jml.2016.11.006
Bates, D., Kliegl, R., Vasishth, S., & Baayen, H. (2015). Parsimonious mixed models. arXiv. https://doi.org/10.48550/ARXIV.1506.04967
Kliegl, R., Kushela, J., & Laubrock, J. (2015). Object orientation and target size modulate the speed of visual attention. Department of Psychology, University of Potsdam.
Kliegl, R., Wei, P., Dambacher, M., Yan, M., & Zhou, X. (2011). Experimental effects and individual differences in linear mixed models: Estimating the relationship between spatial, object, and attraction effects in visual attention. Frontiers in Psychology. https://doi.org/10.3389/fpsyg.2010.00238
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