EDIT:
The majority of papers in this field rely heavily on good ole' n-way repeated measures ANOVA's. I noticed that when cleaning the data the underlying distributions for the participants were all over the place and I was going to chuck away that variability when I aggregated their scores the way normal fixed effects-only ANOVA's require me to. I read somewhere that this might lead to an increase in type 1 errors. I don't know if this illustrates the point...
When running a garden variety 3 way repeated measures ANOVA:
Df Sum Sq Mean Sq F value Pr(>F)
load 1 12.0 12.014 103.679 <0.0000000000000002 ***
comp 1 0.3 0.259 2.237 0.1349
sal 1 0.0 0.014 0.117 0.7320
load:comp 1 0.1 0.052 0.451 0.5017
load:sal 1 0.0 0.017 0.148 0.7000
comp:sal 1 0.1 0.147 1.268 0.2601
load:comp:sal 1 0.5 0.489 4.224 0.0399 *
The maximal MLM:
Df Sum Sq Mean Sq F value
load 1 11.2885 11.2885 116.0419
comp 1 0.0704 0.0704 0.7236
sal 1 0.0090 0.0090 0.0930
load:comp 1 1.0643 1.0643 10.9405
load:sal 1 0.0282 0.0282 0.2900
comp:sal 1 0.0003 0.0003 0.0032
load:comp:sal 1 0.2287 0.2287 2.3506
The main interaction of interest is usually the two way interaction between load and comp, or, in my case, the three way interaction.