In contrast to the APS improvement metrics, the number of levels
completed metric was marginally associated with baseline auditory at-
tention only, suggesting that this metric is less sensitive than the APS
improvement metrics to frontotemporal plasticity, and instead may re-
flect participants' capacity for task engagement and ability to selectively
attend to training exercises. Given that matching or surpassing one's
baseline score is the only requirement for progressing through the
training levels, the total number of levels completed does not account
for the extent to which auditory learning has occurred — it merely indi-
cates that it has occurred. In addition, the number of levels completed
may be susceptible to influence from various non-cognitive factors,
such as participant motivation, fatigue, need for breaks, etc., and it
therefore appears to lack the richness of the APS improvement metrics
for quantifying auditory learning.