Introduction
Using wood for construction and interior design has a long tradition especially in countries like Austria, Canada, Estonia, Finland, Japan, Norway, Sweden and the US. The main reasons for choosing wood in interior settings are aesthetics, a good atmosphere, a healthy climate, hygienic factors and reducing the risk of allergies. Additionally, wood products are preferred as wood has a more favorable environmental profile, contributes less to the greenhouse effect and has less solid waste than other materials. However, the choice of using wood as indoor material depends not only on environmental, hygienic and aesthetic reasons; psychological or emotional attributes of wood also come into play, as wood is perceived as warmer, more attractive, more homely, more relaxing and inviting . In these studies, wood is usually compared to other materials like ceramics, glass, paper, leather, stone, and plastic. Different surface structures or color preferences might have an effect on the psychological perception of different materials. Hence, a question arises if wood is assigned different psychological attributes when compared to a material that appears visually equal.
Similar material to wood is laminate. Previous studies analyzing the psychological perception of laminate and wood did not specify which kind of laminate product was used. In the present study, we use the term laminate as a short term for recycled wood (plywood) composed of laminations. Laminate has a similar appearance and is commonly used as a substitute for wood. Modern techniques in the manufacture of laminate make it difficult to detect visual differences between laminate and wood. Nevertheless, studies show that by haptic evaluation, wood and laminate are perceived differently. Therefore, the aim of the present study is to compare wooden and laminate materials with a visual and haptic evaluation to investigate which psychological criteria are able to differentiate between wood and laminate.
Psychological Attributes of Materials
The majority of product evaluation studies investigate practical functions or aesthetics of the product, such as design, workmanship, value, assemblage or security. Psychological aspects of the products are usually not focused on, with the exception of symbolic values. Symbolic values refer to socially determined symbolic meanings that may evoke thoughts, feelings and associations which are linked to the product. Symbolic values include aspects like modern, simple, expensive, businesslike, sympathetic, creative or captivating. Symbolic values like being elegant, innovative, luxurious or prestigious also show stronger relationships with customer satisfaction than other non-symbolic attributes like functionality or aesthetics. Another important symbolic value is eco-friendliness, which can also be found in different studies. In addition to symbolic values, products can evoke emotional responses. Products can be intentionally designed to create an emotional response (affective engineering; “kansei”) in order to captivate people at an emotional level and improve the value of the product [19]. In this sense, products can be perceived as pleasurable, joyful, satisfying, surprising, trustworthy or even as shady, disappointing or disgusting. According to Desmet and Hekkert [23], these emotions may result from product perception, e.g., playing with a kangaroo ball could lead to emotions such as enthusiasm or happiness; therefore, the kangaroo ball is rated as being able to raise enthusiasm and able to make one happy. Desmet and Hekkert categorized three classes of product emotions: appealingness (which includes emotions such as love, attraction or disgust), praiseworthiness (emotions such as admiration, appreciation or disappointment), and desirability (emotions such as jealousy, enthusiasm, happiness). In a further adaptation, the three categories of product experience are distinguished into aesthetic pleasure, attribution of meaning, and emotional response . All three product experiences are intertwined and can influence product evaluation. These studies mainly focus on the emotional responses that products might induce. Other psychological attributes—such as stress-reducing, activating or able to raise performance or communication—are less often investigated. One notable example is the study of Harbich and Hassenzahl, where behavioral patterns of products are analyzed. In their study, products can be given attributes such as being able to enhance creativity or performance
Psychological Attributes of Wood and Wood Products
Past research investigated the effects of wooden interiors on the individual: Wooden floors are perceived as more pleasant, attractive, healthy, durable, and ecological acceptable compared to carpets. In addition, wooden materials are described as warmer, more natural, more homely, more relaxing and more inviting than ceramics, glass, paper, leather, stone, and plastic materials. Further, rooms with wooden interior stimulate participants to relax or lie down, whereas interiors without wood induce activities such as working or exercising . Wood is also associated with health-promoting characteristics such being stress-reducing: Kelz, Grote and Moser showed that wooden floors, ceilings, cupboards, and wall panels have a positive effect on the individual’s stress level, indicated by a lower heart rate and higher heart rate variability.
A similar result could be found in another study where a room with a wooden floor and walls partly covered with wood increased the individuals’ heart rate variability and lowered the individuals’ diastolic blood pressure. Furthermore, a wood equipped bedroom enhances the quality of sleep and wooden equipment in offices and classrooms reduces stress and strain [9,28]. Reasons why wood has health-beneficial effects on the human organism have not yet been investigated in detail. One explanation could be that wood is related to indoor climate, where natural, untreated wood used in indoors has a positive effect on acoustics and air quality, thus creating a more comfortable indoor climate . Another theory—attention restoration theory indicates that watching nature stimulates a restoration process, as natural settings require less attention to the surroundings, thus allowing the individual to recover. This restoration process is also possible for nature-based indoor environments, such as potted plants and windows with a view of trees, and therefore can be transferred to wooden indoor settings. These results suggest that primarily the appearance of wood is connected to these positive psychological attributes. However, even when different wood surfaces are compared to each other, color, structure and grain lead to different psychological perceptions. Wood with a rough or untreated surface is perceived as warmer, whereas wood with a smooth surface is evaluated as cooler [8]. Wood is also evaluated differently when different wood species are used. Therefore, it is crucial to compare wood with a material that is visually as similar as possible. By comparing wood to a material with similar color, surface structure and grain the risk of wrongly evaluating color and structure of the material instead of the material itself can be minimized.
Psychological Differences between Wood and Laminate
A material with similar appearance and surface is laminate, which is therefore used as a popular substitute for wood products. Jiménez et al. compared the psychological effects of wood and laminate products with photographs. Wood products are rated as significantly more warm and cozy as well as healthier and physically and mentally more stimulating than laminate products. However, research has shown that natural products are usually preferred over synthetic products, as natural products are perceived as healthier, sensory more attractive, purer, safer and morally justifiable. This so-called “green consumer behavior” motivates consumers to seek and buy green products. In line with these beliefs, consumers are more likely to purchase wood products and are more willing to pay additional money. Compared to laminate, wood is labeled as a more natural material and therefore this assumption might influence this preference of wood over synthetic materials. But even without knowing the type of the material, wood is perceived differently, as shown in the study of Berger et al. They compared to wood and laminate only by haptic perception, without telling their participants the differences between the materials. The results showed that even without knowing the difference between the materials, each material was attributed differently. Untreated wood appeared warmer, rougher and softer, whereas its laminate counterpart was described as colder, smoother and harder. These results suggest that wood is given more positive psychological attributes than laminate, even if participants are not aware of the composition and appearance of both materials. This result indicates that even without being aware of the type and composition of the material, individuals unconsciously assign other psychological attributes to wood compared with laminate products. This perception might be related to the surface structure, which is different for wood and laminate products. When touching a rough material, the effective contact area is smaller compared to smooth materials. Therefore, smooth surfaces have greater heat transport, causing a colder feeling when touching them. This is in line with other studies, where rough materials are rated as more warm, soft and pleasant. Wood is perceived as a rough material and therefore this perception might influence other psychological attributes such as warm, soft and pleasant attributes. Laminate, on the contrary, feels smoother and therefore, attributes such as cold and hard seem to be more common.