Using an intraclass correlation to measure consistency across subjects
Fit a multilevel model
MIXED Y /FIXED= | SSTYPE(3) /METHOD=REML /PRINT=SOLUTION /RANDOM=intercept | SUBJECT(participant) COVTYPE(VC).
The intraclass correlation which measures the consistency of performance across version of the participants equals
Variance Component for Participant / [(Variance Component for Participant) + (Variance Component of Residual)]
This can also be computed from a one way repeated ANOVA if there are the same number of repetitions (e.g. time) per participant.