During our daily life, we came across many sensations. The sensation or feeling of touch is the one we encounter mostly and very clearly. This sensation helps us recognize the texture (rough or smooth) of the material we are touching immediately and after that our brain tells us the type of material based on its stored sensation vocabulary. This judgement about material perception is called “Shitsukan” In Japan, “which means that how human brains make sense of material quality. Shitsukan (質感) is a Japanese word whose literal meaning is the sense (kan, 感) of quality (shitsu, 質), and it is commonly used to cover the wide range of topics to which material perception in a broad sense is assigned.
The material quality, mean the properties of materials, such as whether they are gloss or matt; wet or dusty; metal or ceramic and so on”. This science or this behavior of human brain can be the basis of incorporation of artificial intelligence in textiles. This science can be applied to any material type however in this blog I would try to cover this topic with special focus on textile materials, so that my readers may have a basic knowledge of the relationship between science and textile materials.
As mentioned above Material perception, or Shitsukan perception, is about the perception and recognition of a material type, properties, surface quality such as glossiness, translucency and texture, or internal state of an object. This perception and recognition is based on sensory stimuli such as visual, tactile, and auditory sensations. The shitsukan is perceived via our five senses. For example from the surface of an object we touch, we can feel and tell which material is used to make it. Quite often during the buying of textiles in our daily lives we try to feel and decide weather the fabric is comfortable or not. This is called the qualitative judgement of the shitsukan of a fabric. In recent years, numerous studies have attempted to understand the perception mechanisms of shitsukan. To efficiently design shitsukan of a product it is important to quantify it, and studies have reported the methods of quantifying the perceived impression of materials in terms of, the appearance, touch and visual shitsukan.
Information obtained through material perception is associated with our actions toward an object. Because the physical processes leading to sensory signals related to material perception is very complicated, therefore is very difficult to create an experimental stimuli in an efficient way. However, that situation is now changing thanks to advances in technology and knowledge in related fields. In this blog, I will review what is currently known about the neural mechanisms that is responsible for material perception. It has been found that the cortical areas in the ventral visual pathway are strongly involved in material perception.
Therefore, in this blog my focus will be on vision. Surface quality and object appearance, as well as the feel of a finish or texture are also tightly related to one’s preference/aversion or emotional reaction toward an object. Despite material perception being biologically very important, the understanding of its hidden mechanism has not progressed very much. However, because of advancement in the fields of computer graphics and vision, the technology involved in the analysis and simulation of the interaction between light and object, it is now possible to generate and use stimuli simulating objects with various surface qualities.
What kind of information is involved in material perception?
The interaction of light with objects having specific surface meso-structures and optical properties produces various structures within the retinal images of objects, and these structures are the source of generation of a variety of surface qualities. In addition to this, other sensory modalities are also involved in material perception. For instance, when we see a sweater made of fine wool, we can perceive that it will be soft and warm, or we can sense that a metal cup will be cold and hard to the touch. Therefore, the information obtained through different sensory modalities is closely linked with each other in material perception. In this blog I will review cross-modal aspects of material perception including following.
- Neural processing of surface qualities, particularly the glossiness that can be named as “GLOSSINESS PERCEPTION”.
- Neural processing of surface meso-structures, that is another important property and is closely linked to material perception named as “NATURAL TEXTURE PERCEPTION”.
- Neural processes involved in categorization of materials and recognition of various material properties, such as roughness and hardness, based on information about surface glossiness, natural textures, and so on. It can be called as “RECOGNITION OF MATERIAL CATEGORY AND ITS PROPERTIES”.
Now it is very difficult to cover all of the above modalities in one go therefore, I will elaborate all of the above modalities one by one in my next blogs.
- Komatsu H, Goda N. Neural mechanisms of material perception: Quest on Shitsukan. Neuroscience. 2018 Nov 10;392:329-47.