Which ornamental features of bamboo plants will attract the people most?

Highlights

• Plant architecture and design have a significant effect on how people perceive them.

• Ornamental bamboo features were assessed by eye-tracking and questionnaire survey.

• Fixation count reveal the participant’s preference to stem color and leaf and stem stripes.

• People prefer natural traits due to latent conscious belief and social adaptation.

• Abnormal traits draw people's visual focus by increasing dwell time percentage.

Abstract

Plant structure and architecture have a significant influence on how people interpret them. Bamboo plants have highly ornamental attributes, but the traits that attract people the most are still unknown. Therefore, to assess the people's preference for ornamental features of bamboo plants, eye-tracking measures (fixation count, percent of dwell time, pupil size, and saccade amplitude) and a questionnaire survey about subjective preference were conducted by ninety college students as the participants. The result showed that subjective ratings of stem color, leaf stripes, and stem stripes showed a significant positive correlation with the fixation count. The pupil size and saccade amplitude of different ornamental features were not correlated with the subjective ratings. According to random forest model, fixation count was the most influential aspect affecting subjective ratings. Based on integrated eye-tracking measures and subjective ratings, we conclude that people prefer the ornamental features like green stem, green stem with irregular yellow stripes or yellow stem with narrow green stripes, leaves with less number of stripes, normal stem, and tree. In addition, people prefer natural traits, for instance, green stem, normal stem, and tree, related to latent conscious belief and evolutionary adaptation. Abnormal traits, such as leaf stripes and stem stripes attract people’s visual attention and interests, making the fixation count and increasing the percentage of dwell time. This study has significant implications for landscape experts in the design and maintenance of ornamental bamboo plantations in China as well as in other areas of the world.

Introduction

It is well known that the ideal green space could have beneficial physiological and psychological impacts on society (Rahnema et al., 2019). Visual landscapes and ecology can affect human health and help to relieve tension and improve body regeneration and rehabilitation (Özgüner, 2011). The arrangement of plants and their design has a tremendous effect on how people interpret them (Lindemann-Matthies and Bose, 2007). In certain circumstances, plants are the key aspect of the ecosystem that create an effect on the viewer's mind (Schoen et al., 2009). This concept has been characterized as an environmental preference and has often been regarded as a result of the relationship between the environment and the perceived potential for restoration (Wilkie and Clements, 2018; Smith and Moore, 2013). Several studies have evaluated environmental preferences to the aesthetic aspects of natural beauty through psychophysical approaches (Scott et al., 2020; Chang et al., 2008). Their results indicate that environmental preferences are strongly related to environmental features and visual stimuli (Al-Samarraie et al., 2018; Avolio et al., 2015; Hofmann et al., 2017). However, there is a need to explore the relationship between visual attentions determined by physiological measures and stated preference to stimuli as the physiological response indicating visual attention to specific features is unknown.

The use of eye-tracking technologies to analyze visual attention and behavior is meaningful (Dixson et al., 2011). Eye-tracking technology measures the visual intentions by monitoring the participant's gaze fixations and the length of the stimulus fixation (Behe et al., 2020). Eye-tracking also can be a complementary approach to subjective preference (Dudinskaya et al., 2020). Combined with subjective preference methods with eye-tracking technology are the potential methods to reveal visual attention to specific characteristics (Meyerding and Merz, 2018).

Eye-tracking may have the potential to explain the individual preference in eco-friendly plant characteristics (Khachatryan et al., 2017), choice of market productions (Behe et al., 2013), visual plant traits, colors, seasonal color change, and personality traits (Ho et al., 2015; Hofmann et al., 2017; Al-Samarraie et al., 2018; Paraskevopoulou et al., 2018). Many studies have combined self-reports with eye-tracking technologies to reveal preference and visual attention (Behe et al., 2015; Ho et al., 2015). People may be more appealing and fascinating as they provide visual attention to stimuli (Dixson et al., 2011; Maner et al., 2008). Visual manipulation could influence stated preference by increasing the attractiveness (van der Laan et al., 2015) and key features might cause a higher fixation count (Orquin and Mueller Loose, 2013). Besides, visual attention may highly correlate with fixation duration and fixation count (Behe et al., 2015, 2020).

Fixation count and dwell time on stimulus have been considered as a judgment of attractiveness (Behe et al., 2015, 2020). Looking longer at stimulus (referred to as ‘gaze bias’) is attributed to the down-stream effects of dwelling time and fixation count (van der Laan et al., 2015), which is probably caused by the process of top-down attention (Orquin and Mueller Loose, 2013). Saccade amplitude determines the fixation duration (Nattkemper and Prinz, 1987) and the shorter saccade suggests that the participants have reduced their attention (Russo and Rosen, 1975). People spend longer time and more fixation count on their preferred colors (Lee et al., 2005). A study on green space plants in the United States illustrates specific characteristics, such as tree shape and size, but neglected plant color, which is one of the main factors that determine the importance of green spaces (Gudin, 2017). Color is one of the most observable and prominent features of social life so that one can anticipate some of the traits of individuals and societies by observing colors in urban environments. In addition, gaze pattern reveals that people prefer an attractive stimulus with more fixation count and longer dwell time (Hall et al., 2011). Previous studies have suggested that attractiveness and preference tend to be relevant to pupil size (Hess and Polt, 1960). The relationship between stated preference and visual attention to bamboo plants is unknown. Therefore, in the present study, dwell time, fixation count, saccade amplitude, and pupil size were considered as the attractiveness of participants in measuring beauty or personality traits. However, neither survey employed eye-tracking to create user perceptions for ornamental attributes of bamboo plants.

There are over 1600 species of bamboo species worldwide (Vorontsova et al., 2016), and China is growing a significant number of bamboo species and cultivars with high aesthetic value and ornamental interest (Shi et al., 2014). Several bamboo plants have been introduced to landscape green spaces in the United States and Europe owing to their exceptional horticultural interests (Crompton, 2006). The ornamental features in bamboo species are expressed in stem color, leaf stripe, stem stripe, stem variant, etc. Compared to flowering plants, foliage plants are less attractive to humans (Rahnema et al., 2019). The relationship between stated preference and visual attention depends on their attributes (Krucien et al., 2017). For instance, a saliency-based method use for visual assessment and suggests that color and size of the landscape have been the influential factors causing the difference of scenarios (Dupont et al., 2017). Previous studies demonstrate that higher visual saliency would make the stimuli more likely to maintain visual attention (i.e. higher percent of the time spent) and hence increase the stated preference (Krajbich et al., 2010; van der Laan et al., 2015; Bialkova and van Trijp, 2011).

Bamboos are well known to have highly ornamental qualities, but there is no evidence on which characteristics of ornamental bamboo are more preferred by people. To the authors' understanding, this manuscript is the first to examine the connection between visual recognition and audience experience. In this study, we addressed the following questions: (1) which feature of ornamental bamboos would attract people most? (2) How about the measures of eye-tracking when people received the visual stimulation? (3) which measures of eye-tracking were highly related to the preference of ornamental features of bamboos? By addressing these questions, we conducted eye-tracking experiments and questionnaires to evaluate the visual preferences of people and the perceptual quality of different bamboo features.