70 Impact of Fuzzy ARTMAP Match Tracking Strategies on the Recognition of Handwritten Digits

Applying fuzzy ARTMAP to complex real-world problems such as handwritten character recognition may lead to poor performance and a convergence problem whenever the training set contains very similar or identical patterns that belong to different classes. To circumvent this problem, some alternatives to the network's original match tracking (MT) process have been proposed in literature, such as using negative MT, and removing MT altogether. In this paper, the impact on fuzzy ARTMAP performance of different MT strategies is assessed using different patterns recognition problems — two types of synthetic data as well as a real-world handwritten digit data. Fuzzy ARTMAP is trained with the original match tracking (MT+), with negative match tracking (MT−), and without MT algorithm (WMT), and the performance of these networks is compared to the case where the MT parameter is optimized using a PSO-based strategy, denoted PSO(MT). Through a comprehensive set of computer simulations, it has been observed that by training with MT−, fuzzy ARTMAP expends fewer resources than other MT strategies, but can achieve a significantly higher generalization error, especially for data with overlapping class distributions. Generalization error achieved using WMT is significantly higher than other strategies on non overlapping data with complex non-linear decision bounds. Furthermore, the number of internal categories increases significantly. PSO(MT) yields the best overall generalization error, and a number of internal categories that is smaller than WMT, but generally higher than MT+ and MT−. However, this strategy requires a large number of training epochs to convergence.