This Traditional Japanese Floor Mat May Ease Stress, Study Finds

Igusa Grass: The Ancient Japanese Flooring That May Melt Away Stress

Sit down for a stressful mental test, and probably no one thinks twice about what’s underfoot. But what if the flooring beneath a chair, not the room’s temperature or lighting, actually changed how the brain handled pressure? That question sent a team of researchers at Kyushu University looking at a material most Americans have never touched: Igusa, a woven rush grass long used in Japanese home flooring.

For generations, many in Japan have believed Igusa brings a calming quality to a room, but its effects on the brain and mood in a living-space setting had not been thoroughly tested before. Researchers wanted scientific evidence, not just tradition, so they built a small, controlled experiment using real people, brain-wave sensors, and two very different mats.

In the experiment, participants performed a mental task faster, showed distinctive brain-wave activity, and reported feeling steadier against tension and anxiety while sitting in a room with an Igusa mat, compared with a plain plastic one. The study, published in the journal Scientific Reports, was small, but the results point to something worth watching: natural materials in everyday surroundings might shape how minds handle stress.

Seventeen Volunteers Compared Two Mats Over Two Sessions

Scientists recruited volunteers through a bulletin board at Kyushu University. After screening out smokers, people with scent sensitivities, and those uncomfortable in small enclosed spaces, 18 people enrolled. One dropped out partway through, leaving a final group of 17 participants, 10 men and 7 women, with an average age of about 21 and a half years old.

Each participant sat inside a small, soundproofed test room, once with an Igusa mat on the floor and once with an unscented plastic mat, on two separate days about two weeks apart. This setup, called a crossover design, meant every person experienced both conditions, so each participant served as their own comparison point. Researchers say this approach makes findings more reliable even with a modest number of participants.

While seated on the mat, volunteers wore sensors that tracked electrical activity across the scalp, a method called an EEG that measures brain activity in real time. Before and after a visual attention task, they filled out mood questionnaires and rated their impressions of the room’s smell. Meanwhile, sensors in the room tracked temperature, humidity, and carbon dioxide levels.

Chemical tests on the mat itself picked up several natural compounds, including one associated with a green, grassy smell and others linked to a sharper, more bitter scent. A common plastic additive turned up in the control mat instead, but not in the Igusa mat.

Reaction Times Sped Up Without Sacrificing Accuracy

During the task, which asked participants to visually tell shapes apart on a screen, reaction times were quicker with the Igusa mat than with the control mat. Accuracy stayed about the same in both conditions, meaning people weren’t trading correctness for speed; responses simply came faster when Igusa was in the room.

Brain-wave data lined up with that pattern. Beta-wave activity differed at several scalp locations during the task, particularly toward the front of the head. Researchers also calculated a separate engagement index, a measure used elsewhere to gauge how locked-in someone is on a task, and found it was higher with the Igusa mat present.

Mood questionnaires told a related story. Out of several emotional categories tracked, only tension and anxiety showed a real difference between the two mats, improving significantly more with the Igusa mat than with the control mat. That points to a specific kind of stress relief rather than a blanket mood boost across every category.

Smell ratings backed up the idea that people simply liked the Igusa mat more. Volunteers rated its aroma as stronger, more pleasant, more relaxing, and more antique than the plastic mat, which was rated as more modern. The EEG recordings also differed between the two conditions, though the study could not establish whether those differences were caused by the aroma itself.

Rooms With Igusa Mats Kept a Steadier Humidity Level

One of the more unexpected findings had nothing to do with brains at all. It concerned humidity. Rooms with the Igusa mat kept a more stable humidity level across the session, holding around 40 percent before and after the task. The plastic-matted room, by contrast, saw a small rise in humidity over the same period that researchers said was unlikely to be random chance. Igusa is known to absorb moisture, which may explain why it helped keep the room’s air steady. Temperature and carbon dioxide levels didn’t differ in any real way between the two mat conditions, though carbon dioxide trended slightly lower with Igusa present.

Small Sample Size Limits the Findings’ Reach

None of this means new flooring will cure anxiety or turn anyone into a productivity machine overnight. Researchers noted that the calming effect showed up specifically in tension and anxiety scores, not across every mood measured, and that familiarity with a traditional material could have colored people’s reactions. Still, faster reaction times, distinct brain-wave patterns, and steadier emotional responses under the Igusa mat build a case that natural materials in a home aren’t purely decorative; they may interact with the nervous system in ways researchers can measure. A floor covering that has been part of Japanese homes for generations, it turns out, might have been doing more than looking nice underfoot the whole time.

---

Disclaimer: This article summarizes findings from a peer-reviewed scientific study for general audiences and is not medical advice. The results come from a single small experiment and have not yet been confirmed by larger or more diverse studies.

---