Katsuya Ujimoto (Ricoh)
Results
Measurements showed that NH3 (ammonia) and the S, M, and L molecular ranges were not uniformly distributed throughout the urban environment but exhibited characteristic spatial distributions and temporal variations depending on location.
In Yoyogi Park, relatively high NH3 signals were observed over a wide area, together with localised hotspots in the M and L molecular ranges. Areas where fallen leaves had accumulated showed increased FAIMS signals, and Chiyoko displayed intensive exploratory behaviour such as running and digging. In open areas of the park, increases in FAIMS signals coincided with Chiyoko’s exploratory behaviour, suggesting that both responded to molecules carried by the wind.
In Harajuku, S and M signals remained relatively stable, whereas L-range signals appeared as brief, intermittent events. Chiyoko occasionally paused near luxury boutiques, variety shops, a capybara café, and narrow intersections surrounded by buildings, but more often she briefly investigated before resuming her walk. These localised events may reflect either moving odour sources or intermittent volatile compounds generated by pedestrian traffic and commercial premises.
In many observations, increases in NH3 preceded increases in the S, M, and L signals, indicating a consistent temporal sequence.
Discussion
Comparison between Yoyogi Park and Harajuku suggests that differences in the spatial structure of odours strongly influenced Chiyoko’s behaviour. In Yoyogi Park, naturally occurring elements may have retained odour molecules and formed stable concentration gradients, encouraging sustained exploratory behaviour and locally elevated FAIMS signals. In Harajuku, odours originating from pedestrian activity and the built environment were more diverse and intermittent, producing unstable odour gradients. Chiyoko therefore often detected odours but ended her investigation at an early stage.
These observations suggest that, for Chiyoko, olfactory meaning depends less on odour intensity than on the structure of the olfactory field. At enclosed intersections, transient increases in FAIMS signals coincided with indecisive exploratory behaviour, suggesting the existence of an olfactory chaotic space created by changing wind direction and turbulence. By contrast, open areas and locations with accumulated leaves produced simultaneous responses from both FAIMS and Chiyoko.
The observations also suggest a two-stage olfactory model. Variations in NH3 concentration may first function as a trigger for detecting unusual environmental conditions. As the source is approached and molecular concentrations increase, patterns within the S, M, and L molecular ranges may then provide qualitative information about the odour. This model is consistent with Chiyoko’s behavioural sequence of detection, running, stopping, digging, or ignoring.
The average NH3 concentration remained below approximately 17 ppb, although local peaks of 100–400 ppb were observed. These results suggest that Chiyoko perceives subtle environmental changes that often remain below the threshold of human perception. Parallel FAIMS measurements made part of this otherwise imperceptible olfactory environment measurable.