# Discrimination Accuracy of Sequential Versus Simultaneous Vibrotactile Stimulation on the Forearm
## 5 Discussion  
We introduced a novel approach to presenting vibrotactile stimulation patterns with a forearm-mounted wearable vibrotactile sleeve, where Braille-like patterns were conveyed with tactile actuators. Our investigation focused on comparing the effectiveness of sequential versus simultaneous presentations of vibrotactile stimuli, as well as evaluating the influence of pattern length on recognition accuracy.  
The results provide evidence in support of sequential over simultaneous stimulus presentation. We observed a vastly higher average accuracy rate for sequential (93.24%) presentation than simultaneous (26.15%). It is nevertheless important to note that the total stimulation time was lower for simultaneous presentation (1000 ms) than sequential, which could take from 1450 ms (for two activations) to 4300 ms (for five activations). This difference in presentation time affects how much information can be transmitted and is a question that needs to be addressed in future studies.  
It is also important to consider the practical implications of sequential versus simultaneous presentation. In real-world scenarios (such as reading Braille text), the efficient retrieval of information is crucial. The practicality of any Braille design therefore involves a delicate balance between accuracy and speed. Although this aspect was not the primary focus in this phase of study, it is nevertheless a consideration to be addressed in future research.  
Furthermore, we observed large accuracy differences between the two vibrotactile pattern lengths (long versus short). Accuracy was significantly higher for the short patterns requiring 2-3 actuators than the long patterns requiring 4-5 actuators. Pattern length, therefore, has a large effect on accuracy, with short patterns leading to higher perceptual accuracy. This difference was seen for both simultaneous and sequential presentations. But here again, we should note that more information can be conveyed with longer patterns, and future studies need to determine the optimal combination of stimulus time and pattern length for conveying tactile information. It is also important to consider to what degree these differences between short and long patterns may reflect different demands on working memory and increased s for responding.  
Moreover, we investigated potential learning effects on pattern recognition accuracy across the six blocks. The results revealed a consistent improvement in average accuracy over time, indicating that participants were able to improve their ability to reproduce the vibrotactile patterns. This was also the case for simultaneous presentation, although performance levels remained relatively low.  
Overall, our findings emphasize the importance of considering stimulus presentation methods and vibrotactile pattern lengths when designing experiments related to haptic pattern recognition, in addition to taking learning into account. These insights are crucial for the development of effective vibrotactile pattern recognition devices and training programs.  
We also investigated any potential serial position effects, which can shed light on the effects of the order of stimulus presentation on perceptual recognition. We observed both a primacy effect (better performance for stimuli at the beginning of a sequence) and a recency effect (higher accuracy for stimuli at the end of a sequence). Performance was, on the other hand, slightly poorer for activations during the middle of the sequences than for the initial and final stimuli.  
Regarding the differences between presentation modes, during sequential activation, participants have the advantage of analyzing the activations one at a time, using their working memory to process and identify patterns. Conversely, simultaneous activation requires rapid, concurrent processing of multiple activations, which may surpass their working memory capacity.