# Touch, Texture and Haptic Feedback: A Review on How We Feel the World around Us
## 4 Haptic Feedback  
Haptic feedback systems are generally classified into two main types based on the type of feedback that they provide. They are classified as cutaneous feedback and kinesthetic feedback. Figure 1 shows several different cutaneous and kinesthetic feedback devices currently being developed. Both kinesthetic and cutaneous feedback devices have their own differences and roles in haptics and understanding these strengths and limitations will allow for the development of new technologies.  
Kinesthesa or proprioception is defined as a person's perception of body movement [79]. Mechanoreceptors within the joints and muscles send signals to the brain that allow a person to effectively judge movement and motion. Proprioception is an important aspect of daily life as it effectively allows a person to \"judge limb movements and positions, force, heaviness, stiffness, and viscosity\" [80]. Kinesthesa is important in that it is one of the body's main tools for judging the amount of force being exerted on any given object; however, this can be difficult when applied to virtual reality simulations as the lack of a proper and tangible object can adversely affect a person's perception of weight [81].  
The second type of haptic feedback system is the cutaneous feedback system. Cutaneous feedback refers to all the stimuli received by the mechanoreceptors located in the skin and is generally being referred to when discussing the sense of touch. Touch is responsible for the detection of pressure and vibration stimuli and is most concentrated at the fingertips [82]. The vibrations caused when gripping or holding an object are what determines the amount of force required when grasping to avoid slippage [83]. Beyond the real-world implications of cutaneous feedback, studies have shown the various effects of incorporating tactile feedback in virtual reality simulations. It was found that the implementation of cutaneous feedback can greatly improve the weight perception of users even in the absence of kinesthetic feedback [81; 84]. [PERSON] et al. cited in their study using their haptic shear system, HapTip, that the presence of cutaneous feedback can significantly improve pattern recognition and weight distribution of virtual objects [85]. Another study has also shown that cutaneous feedback significantly improved the user's force estimation when holding objects [86]. Other studies have also shown significant improvements when conducting various tasks within the virtual environment such as writing, puzzle solving, hand-based movement exercises, and the distinguishing of curved surfaces [75; 87; 88; 89].  
Figure 1: An example of both cutaneous and kinesthetic feedback devices that show the (**a**) hRing which utilizes skin stretch, reprinted with permission from [75], (**b**) TacTiles which utilize electromagnetic brakes for applying pressure, reprinted with permission from [76], (**c**) LucidVR, string-based actuators, retrieved from [77], and (**d**) ExoTen which utilize McKibben-based artificial muscles, reprinted with permission from [78].  
Unlike kinesthetic feedback, achieving accurate and believable cutaneous feedback is a significantly more difficult challenge.  
An ideal haptic device should incorporate both kinesthetic and tactile feedback within itself to better simulate how human skin interacts with objects, with the device capable of locking the hands and fingers when holding or gripping a virtual object to simulate kinesthesis and an actuator to provide haptic feedback either through indentation, vibration, or other similar means, as shown in Figure 2.