According to Erikson’s stages of psychosocial development, college years are when one must perform the basic development tasks of establishing self-identity and personal maturity (Kim, 2009). During this time, university students feel psychological burden due to issues such as choosing their future career path, anxiety about the future, and adapting to changes in the social environment (Kim et al., 2014). They are also facing constant life stress in the rapid changes of society in addition to adjusting to college life, such as academic achievement, career path, and new interpersonal relations (Lee, 2012). Stress of university students makes it difficult to adjust to college life and causes problems such as anxiety and depression. University students sometimes smoke or drink to cope with such stress, and some even end up being addicted (Bae, 2019). This stress university students suffer from as well as maladaptive coping is known to deteriorate academic achievement and life satisfaction (Suldo et al., 2008). Stressful life events cause psychological and physical problems for individuals, making it difficult to adjust to everyday life. Therefore, it is an important matter in their lives to properly handle stress toward a positive direction during college years (Kim, 2012).

Horticultural activities using plants have a positive effect on the stress, depression, and self-esteem of participants (Park et al., 2016), reduce anxiety or depression, and increase life satisfaction (Kim et al., 2012). Floral decoration increases stability of adults and is also effective in relieving stress (Tak, 2006). Floral design is classified into cut flowers, potted flowers, and preserved flowers. Pressed flowers, a type of preserved flowers, are real flowers dried to be used semi-permanently but are still natural compared to artificial flowers (Condon, 1962). Art activities using pressed flowers are a type of plastic arts formed by emphasizing the pictorial mood after artificially pressing and drying the flowers, leaves, and stems of the plant body, using physical methods or chemical treatment (Yang et al., 1997). One may feel the joy of creation in the process, and it is a creative arts activity as good as painting but requires relatively less time or effort (Yang et al., 1997). It can be used easily by anyone in daily life and also be applied to household items in addition to artwork (Condon, 1962). Working with pressed flowers relaxes the anxious mind and body, lowering the accelerated vitality and forming a balance (Kim et al., 2012). There is a study result that collaborative programs of pressed flowers and floral decoration are also effective in improving life satisfaction and interpersonal relations among the elderly in convalescent hospitals (Jeong et al., 2017).

Recently, various studies are being conducted to examine the physiological changes in emotional functions, and among tests that can objectively examine the physiological phenomena of humans, electroencephalogram (EEG) provides quantitative data for psychophysiological research of quantitative brain functions (Chang and Chen, 2005). Spontaneous electrical changes occur in response to stimulation in the brain, which is a central nervous system, and these changes are measured through EEG. EEG is an objective and non-invasive method that records real-time electrical changes that occur due to the brain cell activity and can sequentially identify constantly changing brain activity (Yoon, 2010). The frontal lobe is the part that directly creates the mind, which is the human spirit, by performing a key role in cognitive function and thinking, and also generates human creativity and is closely related to emotions like pleasure. Frontal EEG can be used as an important indicator in interpreting human mental activity (Bak, 2011). Meanwhile, most of the traditional devices used to acquire EEG signals used at least 16 electrodes, but the process or actions required for measurement are too many or complicated, making it difficult to apply to children or other participants that are sensitive to stimulation (Badcock et al., 2013; Johnstone et al., 2012). A simplified EEG device produces consistent measured values even with repeated measurements, and these measured values are highly correlated with those of the traditional multichannel EEG device (Ratti et al., 2017; Rogers et al., 2016), and thus can effectively measure and classify various cognitive conditions such as relaxation, attention, sleeping, and awakening (Fernandez-Blanco et al., 2020; Kang et al., 2015; Peng et al., 2019).

Accordingly, this study examines the effect of making pressed flower fans on the activation of prefrontal θ waves, α waves, β waves, and ϒ waves of university students and investigate the psychophysiological effectiveness of horticultural activities using preserved flowers.

This study analyzed EEG using pressed flowers, which are preserved flowers, as a pilot test to investigate the healing effects of plants by type of use and activity of flowers that serve as the medium of healing in horticultural therapy. The program was developed in three stages, making fans decorated with pressed flowers while wearing an EEG device: ① preparation stage: looking at a wall coated with white paint (2 minutes) ② work stage: designing pressed flowers on a fan (5 minutes) ③ appreciation stage: staring at and appreciating the fans they made, decorated in pressed flowers (3 minutes). Total relative values were analyzed by dividing the sections of prefrontal θ, α, β, and ϒ waves into preparation, work, and appreciation, excluding delta waves that increase in sleep. The results showed that, in the pressed flower fan making program, θ waves that appear dominant in a sleepy or hypnotic state decreased in the work stage, which involves designing pressed flowers of different colors and decorating them with tweezers (p < .01). Moreover, α waves of stability and relaxation increased (p ≦ .001), and β waves that reflect arousal and active mental state were activated (p < .05). Quantitative data proved that working elaborately with tweezers and pressed flowers during the activities had a positive effect on attention in a stable, relaxed state. On the other hand, θ waves increased in the appreciation stage compared to the work stage. This result suggests that internal attention increased during appreciation, and positive brain waves are activated more while working rather than appreciating. In other words, θ waves were activated when simply appreciating the decorated fans, but α waves and β waves related to stability, relaxation, and attention were activated more when actually doing the work. Therefore, it is necessary to select activities that are focused on work or appreciation depending on not only the physical state of the subjects but also the therapeutic purpose. This study may be limited in that it only analyzed the effects of pressed flower work, while not comparing with other activities. In addition, it is also necessary to comparatively analyze different types of flowers, difficulty levels in pressed flower work, and types of artwork. Furthermore, in determining healing effectiveness, an approach based on medical science must be taken by medical specialists so that horticultural therapy can be established as a field of complementary and alternative medicine.