Motor features that distinguish isolated REM sleep behavior disorder patients from healthy controls: A systematic review.

The multisensory experience of a hair salon visit encompasses a rich interplay of visual, olfactory, tactile and auditory stimuli. However, the specific act of hair shampooing presents a unique sensory landscape. Visual input from the shampoo product is minimized for the client as hair is washed by hairdressers, shifting the perceptual focus towards other sensory modalities. While the olfactory and tactile aspects of shampooing—the fragrance of the product and the sensation of scalp massage—have received considerable attention, the auditory dimension remains largely unexplored. Despite extensive research on the physical properties of shampoo foam, including viscosity, texture and stability [] or on their contribution to hair washing, active deposition or tactile perception [], the auditory properties of lathering and foam manipulation during the shampooing process have been notably overlooked. Given the close proximity of the hair to the ears during this procedure, the perceptual responses and cognitive dimension of shampoo foam sound on the overall salon experience remain as questions. The sound of a product and its effect on listeners forms a large part of the user experience. In the automotive industry, for example, psychoacousticians test the relationship between the physical car, the sounds it makes when being used (engine, door opening and closing, etc.), and people's experience of the car and then adjust physical aspects, where possible, to improve the user experience []. Auditory cues can give important information about objects and their function [see [] for a review]. This ranges from shape [] to hardness of objects []; distinguishing between breaking and bouncing events [], and determining the configuration of clapping hands []. Auditory information can also have a strong impact on emotion and affect, which has a close relationship with users’ perception of sound quality [] and of connotations like ‘luxury’ []. Auditory feedback can affect other senses as well; increasing the high‐frequency content or level of the sound while a person rubs their hands together can make their skin feel drier [] and increase the tactile roughness of surfaces []. To create an optimal multisensory experience of a product, the auditory aspect of a product must be taken into account from the initial stages of development; this process is also known as auditory or acoustic design and aims to improve products' sound quality []. People have clear preferences for certain types of sounds, even noises like those made by air conditioners [], electric toothbrush motors [] and hair dryers []. This is true of food products as well; the texture of the food itself can be influenced by the sound it makes when being crunched [] and music and other sounds can affect many aspects of the eating experience, ranging from taste to enjoyment and willingness to pay [see [] for a review]. In cosmetics, the packaging sound has the potential to affect the experience as well; participants can differentiate and categorize the sounds of different lipstick tubes closing []. Multisensory design, including the auditory aspect, has the potential to affect the entire user experience of topical cosmetic and pharmaceutical skincare as well []. By designing the sound made by products alongside the other functional and aesthetic aspects of it, the whole user experience can be improved.