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Technologies of CLST

The “KOKORO scale”, a system to assess human mood or mental state.



Key points 

  • A novel method to quantify subtle changes in daily mood and feelings, based on the collaboration by RIKEN and the Business Innovation Center Osaka (Osaka Urban Industry Promotion Center).
  • Quantitative data analysis of mood changes before and after the Great East Japan Earthquake, which occurred during a preliminary survey
  • Applied in psychological surveys to evaluate “emotional movement” in the fields of academia, government, and industry 



The “KOKORO scale”, which was developed by Cellular Function Imaging Team is a system in which individuals can input mood information simply with a touch panel or other device. It utilizes four-quadrant matrix*1 with measures of mood including feelings of security and anxiety, feelings of excitement and irritability, and level of motivation (feeling considerable motivation and feeling no motivation) on horizontal and vertical axes. The center point of each axis is taken to be 0, with gradations from −100 to 100. Subjects mark a dot at the position showing their current mood every several minutes or several hours, and changes in mood can be expressed between points with a straight line or curve. Intuitive sensations can be expressed on the KOKORO scale without the use of language, for example, as multiple choices or written descriptions; therefore, subtle differences in sensation can be easily quantified.

The first pilot study using the KOKORO scale was conducted from February 8 to March 24, 2011, with the cooperation of the Kao Corporation, to record the daily mood changes in seven homemakers (45–55 years old) living in Tokyo. Coincidently, the Great East Japan Earthquake occurred on March 11, so that by chance consecutive mood data were obtained before and after the earthquake. The data showed quantitatively that after the earthquake, a previously unseen loss in feelings of security and an increase in anxiety, together with a loss of feelings of excitement and an increase in irritability, were observed. These depressions in mood peaked immediately after the earthquake and then the mood gradually recovered, but at the time the study ended (2 weeks after the earthquake) there were still times during the day when mood had not recovered to the pre-earthquake level. Based on statistical data analysis, it was predicted that it would take from 2 weeks to 1 month for mood to recover to the pre-earthquake level. In an actual follow-up survey in June, it was confirmed that mood data had completely recovered to pre-earthquake levels at all times of the day. The quick recovery of subjects’ mood amid continuing aftershocks is thought to be a result of the brain making relative value judgments such as “How is today compared with yesterday?” and “How am I doing compared with others?”

The KOKORO scale can use data input on a touch panel in addition to the conventional method of writing on printed paper, enabling the collection of more detailed daily mood changes or data from large populations. It is promising for application in academic research in fields such as psychology and brain science, and as a marketing tool to evaluate the level of satisfaction with commercial products or impressions when using a service. 


*1 Four-quadrant matrix
A figure with the coordinate plane divided into four by orthogonal crossing of vertical and horizontal axes at the origin. The upper right area is taken to be the first quadrant, and moving counterclockwise the others are called the second, third, and fourth quadrants.



The number of suicides in Japan reaches 30,000 each year, which is a very high figure compared to other countries in the world. In recent years depressed mood and clinical depression in workers caused by the prolonged recession and diversification of working styles has also become a social problem, and there is a plan to make employee stress checks compulsory for businesses with 50 or more employees starting in December 2015. For government services and commercial products and services, on the other hand, conducting preliminary questionnaire surveys during the development process and monitoring impressions of use are general practices. However, mood and feelings change constantly throughout the day, and there are problems with such surveys because memories are not necessarily reliable even if one tries to remember the mood changes during a time gone by, and that subjective impressions are easily influenced by mood and environment at the moment. Moreover, events in daily life and work, use of products, and enjoyment of services does not necessarily produce large psychological effects, and these things are difficult to deal with adequately using questionnaire surveys and other conventional methods under the present circumstances.

To overcome these problems, a means of sensitively and simply capturing the subtle psychological changes that occur in the daily lives of people, in which various random events occur continuously, is needed. There is also a strong need for the construction of systems to create affluent and vital societies and companies by monitoring people’s mood and feelings and providing effective feedback. Therefore, the “KOKORO scale,” was developed for capturing “emotional movement (changes)” with simple touch data input in two-dimensional space on a smart phone or tablet computer. With the KOKORO scale, intuitive sensations (feelings of security, anxiety, feelings of excitement, irritability, level of motivation, etc.) can be directly input. Real numbers in two-dimensional space are then handled as data so that even small psychological changes can be quantified.

Brain science research on fatigue, depressed mood, and volition has progressed in recent years, and there is an increasing need to treat psychological changes as quantitative data. However, most previous psychological surveys have used formats in which responses to questions are given in written statements or by multiple choices, with which it is unrealistic to conduct surveys every several minutes or several hours. As a result, “emotional movements” could not be fully understood. Moreover, it is difficult to express intuitive sensations accurately even with free writing on a survey form, and subtle differences in sensation cannot be quantified when responses are selected from given word choices (for example: Never/Sometimes/Often). Thus, they are not suited to mathematical statistical calculation.

Harvard University’s D.T. Gilbert group conducted a real-time survey of happiness with more than 5,000 people in 83 countries using smart phones and other devices, and reported a relationship between activity and happiness (M.A. Killingsworth et al, Science 330: 932, 2010). Their survey used conventional selection tasks (very bad: 0 points, very good: 100 points), however, and did not quantify dynamic changes in subtle psychology in daily life.

Therefore, our research group developed the KOKORO scale, a four-quadrant matrix with measures of mood established on two axes in two-dimensional space, with feelings of security and anxiety on the horizontal axis and feelings of excitement and irritability on the vertical axis. Preliminary surveys began in 2011 with small numbers of subjects. Use of the KOKORO scale is promising for a quantitative understanding of the level of change in mood in hourly, weekly, or monthly units, and for establishing relative patterns of mood change with activities and events in daily life. 


The application of KOKORO scale –A survey of “emotional movement” before and after the Great East Japan Earthquake–

In cooperation with the Kao Corporation, the study group distributed a paper version of the KOKORO scale to seven homemakers (45–55 years old) living in Tokyo, and had them write their changes in mood every day upon rising and at 12:00, 13:00, 18:00, and bedtime, over 6 weeks from February 8 to March 24, 2011 (excluding the survey form collection days of February 22 and March 9 and 10). The Great East Japan Earthquake occurred on March 11 in the fifth week of the survey, and although the subjects were not direct victims, effects on mood from things such as earthquake-related news reports on consecutive days and scheduled power outages could be acquired from the data. The data analysis was done after anonymizing the individual names.


First, during the normal period before the earthquake (February 8 to March 8) the mean data from the seven women showed characteristic changes with a trend for mild anxiety upon rising, after which this anxiety decreased as noon approached and there was a rising feeling of excitement. However, there was a temporary abatement in the feeling of excitement in the evening followed by the increase in feelings of security and excitement toward bedtime (Figure 1). These characteristics were seen continuously for 4 weeks before the earthquake.

Looking at the averaged data for all subjects acquired from March 11, the day of the Great East Japan Earthquake, until March 24, a sudden loss of feelings of security and an increase in anxiety, as well as a loss of feelings of excitement and an increase in irritability not seen in the pre-earthquake data were confirmed. This depression in mood peaked immediately after the earthquake and afterward the mood gradually recovered. However, the day on which the survey ended (2 weeks after the earthquake), there were still times of the day, such as 13:00, at which mood had still not fully recovered. A regression line*2 was then made for the recovery trends for the 2 weeks after the earthquake and the number of days until returning to the pre-earthquake level were predicted. The results predicted that mood would recover to the pre-earthquake level for all times of the day by 2 weeks to 1 month after the earthquake.



Although this survey concluded on the originally scheduled day (March 24), a follow-up survey using the same KOKORO scale was conducted for 1 week starting on June 6 with the same subjects for the purpose of confirming that mood had recovered after the earthquake. The mean trends for the seven subjects were analyzed. The results revealed that mood data had completely recovered to the pre-earthquake levels in June (Figure 2).

Acquisition of these valuable data was the impetus for the research group to develop an application for touch panel input with the KOKORO scale. With such an application, intuitive mood sensations can be easily input in 2–3 seconds, making it possible to obtain large amounts of data every several minutes or several hours. Moreover, since all data are handled with real numbers, immediate statistical processing can be done using computers and subtle emotional changes can be captured in numerical values. Even with psychological research that was thought to be susceptible to effects from various subjective elements, such as mood and sensations, it has become possible to understand in detail the characteristics of individual mood changes and trends in populations, such as by sex or age group, by mathematically analyzing values that subjects input repeatedly.


*2 Regression lines
This is one means of statistically investigating the relationship between two groups of numerical values. In the present data analysis, a formula was prepared assuming a linear recovery of mood with respect to the number of days that had passed since the earthquake, and the number of days to recover to the pre-earthquake level was calculated.


Other possible cases of application

Many different uses can be imagined for the KOKORO scale, including brain science and psychological research, mental health measures such as early detection of depression and other mood disorders, construction of social systems to mitigate stress and prevent fatigue, improvement of government services, better assessments and sales of commercial products and services, and higher level of customer satisfaction. It may also be applicable in various other fields, such as mental training for athletes and evaluations of the happiness of citizens in a particular city or country. Since quantitative evaluations with numerical values can be done, it is especially promising for use in medical decisions where assessments have been difficult, for example in comparing the effects of treating depression with drugs and other psychological and behavior therapies or the use of supplements. With the introduction of a KOKORO scale application using touch panels for tablet computers or smart phones and the cooperation of users, it will also be possible to easily and continuously acquire large amounts of data on a daily, monthly, or yearly basis. The KOKORO scale may also be expected to serve in understanding the stress levels or psychological state of distant patients or people during a disaster, and surveys of annual changes in happiness of a nation's population or other continuous evaluations.


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CLST was reorganized into three centers according to the RIKEN 4th Medium-Term Plan from April 1, 2018.