Rick,
Yes, the comparisons of model simulated cursors and participant cursors were conducted and are presented in the line graphs, The bar graphs show the fit of the participant cursors to the target.
I don’t disagree that the position control model fits the behaviour well as per the correlations, however, I would say that correlations are a poor measure of temporal asynchrony in tracking (as is RMS as demonstrated in the paper). The leaky integrator position control model is unable to compensate transport delays effectively and the extrapolation model performs substantially better under conditions of delay. In fact, this is a challenge for the position control model because:
- The transport delays are non-negotiable
- despite the transport delays participants sometimes track without a delay
- The position control model cannot compensate this delay
I disagree that the extrapolation model should necessarily have a more accurate fit to both sinusoid and pseudorandom cursor data. I expected that it would because velocity information is available in both cases. However, given that participants don’t exhibit zero phase tracking when tracking pseudorandom signals (they track with a phase delay of about 180ms) this demonstrates that they are not compensating their intrinsic transport delays (as they must be when tracking with <100 ms phase delay for sinusoids). The fact that participants do not appear to utilise velocity information when tracking pseudorandom targets is noteworthy and several potential explanations for this are set out in the discussion…
So yes, the neural transport lag is the same in both cases, but the participants only compensate it when tracking sinusoids (as is seen in their behaviour, irrespective of the model), and suitably, the extrapolation model only fits the cursor data better in that condition.
It may be the case that controlling higher level perceptions could also provide this ability, controlling for the long term pattern of the repeating sinusoid, for instance. One interesting thing, as Adam said, is that controlling cursor velocity - target velocity error does not confer the same advantage (I tried this before simply the target velocity).
Best,
Max