Tactile. It is essential to establish the di↵erence between haptic and tactile user interfaces since both terms are commonly used in assistive technologies research for blind people, and no di↵xxxxxx is stated between haptic and tactile in most dictionary definitions, [13]. The word haptic refers to the sense of touch, being this sense twofold, including cutaneous or tactile touch and kinesthetic touch, [14]. Kinesthetic information refers to all the information acquired through the sensors in the joints, muscles and tendons, including position, velocity and forces of one’s body state. Tactile informa- tion refers to the information acquired through sensors in the skin, including pressure, texture, puncture, thermal properties, softness, wetness, friction-induced phenomena, adhesion, shape, edges and embossing features, [15, 16]. According to [17], the tactile aspect refers to the infor- mation received from the nerve terminals of the skin, while the kinesthetic refers to the dynamic aspects of said interaction with the object. Tactile interaction design in 2D tactile refreshable user interfaces is often developed in conjunc- tion with audio interactions and audio feedback (audio tones, earcons, auditory icons, speech and 3d sound), [18]. Considering that the majority of these user interfaces use audio feedback, they can be classified as multimodal user interfaces or, more specifically, in 2D refreshable audio- tactile user interfaces. It is widely recognised that multimodal user interfaces have the potential to be more intuitive and improve the human-computer interaction when carefully implemented and design, opening doors for accessible computer interfaces and technologies for the visually impaired, [19, 20]. Audio only feedback is ine↵ective in noisy environments, while haptic only feedback becomes ine↵ective in bumpy environments. If the information is provided both in au- dio and haptic format, the message is more reliably received, and the environmental constraints can be solved, [21, 22, 23].
