Original sentence: Recently, Heathcote, Brown, and Mewhort, have suggested that at the individual-level a three parameter exponential function tends to fit observed data better than a three parameter power function
Edited sentence: Heathcote et al suggest that individual-level data is better fit by an exponential function and the authors demonstrate that the multiple exponential curves will average to produce a curve that is misleadingly well fit by a power function.However, subsequent research by Heathcote, Brown, and Mewhort (2000) suggests that the power function observed in learning curves that are averaged across participants is an artifact of aggregation