The Role of Training Duration in Frequency Discrimination of Electrotactile Feedback

Electrotactile feedback is a promising communication channel in various applications, from healthcare to human-machine interfaces. However, the time needed to train the users remains one of the main challenges. This study examines the impact of training duration on user performance when using frequency modulation to convey information through electrotactile stimulation. We have employed an electrotactile stimulation system that includes a custom-designed 32-pad electrode for the thigh and custom-developed software for psychometric evaluation. Software included two electrode activation regimes, i.e., single electrode pad and distributed stimulation with multiple pads, that were used for training, reinforced learning and testing of the discrimination between four frequency levels. The study involved 34 healthy volunteers subjected to short and long training protocols to evaluate the impact of learning. The results showed that longer training significantly improved the recognition, confirming that training duration is a crucial factor for effective electrotactile feedback based on frequency modulation. The training effects were especially pronounced in more complex task, when stimulation was delivered to a randomly selected pad of the electrode array. These findings provide valuable insights for optimizing training duration in electrotactile applications.