Research is all about assessing a single variable and this was accomplished within this study, “the MCR procedure involved four phases: spontaneous baseline (no mobile movement), an uncoupled reactive phase (experimenter triggered mobile movement), tethered phase (tethered foot triggered mobile response), and untethered phase (tethered foot is disconnected and mobile is stationary).” There's also data demonstrating it was much more than just a positive feedback loop highlighted in the research, “the tethered phase peak rate does not represent a set point in time during the tethered phase across infants. Rather, it is a measure of activity across a time window comparable to other time samples (1 min) reflecting maximum activity during the tethered phase across infants. This step allowed peak rate to be compared to movement rates of other experimental phases.” The findings weren't just based on a hey look, they smiled data point. If you dig into the data collection, “the magnitudes of various multidimensional velocity vectors (i.e., between the two feet, between the trigger foot and the mobile, and between the unconnected foot and mobile) were cross-covaried across the first minute of each phase for each infant using the aforementioned method to obtain Pearson r values. Differences between experimental phases were tested using repeated measures ANOVAs.” As a fellow researcher, it seems apparent this displays more than just a positive feedback loop according to the methods and procedures utilized in the study. To write this off as nothing more than a positive feedback loop means your conclusion was drawn before assessing how the information was collected and evaluated.