2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
September 24–28, 2017, Vancouver, BC, Canada

Studying the Effect of Expressive Light Animation on Human
Perception and Behavior of Human-Machine Interaction
Sichao Song1 and Seiji Yamada2I. M OTIVATIONAs robots begin entering human society and interactingwith people, it is important for them to be able to express
affect. Although many studies have investigated human-likeinteraction methods involving facial expressions and gestures, there has been little focus on appearance-constrainedrobots due to their restrictions in interaction modalities.
Existing approaches for promoting affective interaction forsuch robots mainly focused on motion cues or body postures.
However, such approaches lack expressibility and are hard, if
not impossible, to be applied in many application scenarios.
To address this issue, we investigate an alternative modality, expressive light, as an affective interaction modality.
Compared to other modalities such as motion cue, body
posture, and acoustic cue, expressive light offers a muchbroader design space, is less intrusive, and less restricted tospatiotemporal limitations. However until now, it has been
unclear how robots can take advantage of expressive light asa primary modality to express affect, and furthermore, howexpressive light can affect people’s perceptions towards andbehaviors toward the robot.
II. C OLOR P SYCHOLOGY AND E XPRESSIVE L IGHT
A NIMATION D ESIGN
Color psychologists have intensively investigated on various aspects of color, including color effects on psychologicaland biological functioning in particular. Their work primarily
focuses on red, blue, and green, since such colors (especiallyred) have been considered as special and have positive links
in the natural realm. According to the Color-in-Context(CIC) theory, each color activates associations that contain psychologically-relevant messages. Therefore, viewing
a color can influence psychological functioning and foster
motivational and behavioral processes, such as approach oravoidance tendencies. In general, color stimuli that carry apositive meaning produce approach responses, whereas thosethat carry a negative meaning produce avoidance responses.
Accordingly, we designed two kinds of (LED) light animations, low intensive triangle waveform in green color andhigh intensive square waveform in red color. The intension(frequency) and waveform are introduced to amplify thecolor effects and manipulate the perception of light animationin the arousal level. We assume that the green and low

intensive (GL) light animation will be perceived as positive and lowly arousing (pleasing) while the red and highintensive (RH) light animation be perceived as negative andhighly arousing (unpleasing). Further, the GL light animation
may induce people’s approach-like behaviors while RH lightanimation may induce avoidance-like behaviors.
III. E XPERIMENTS AND R ESULTS
To investigate the effect of expressive light animation on
both people’s perception and behavior, we performed a seriesof two experiments using an Ultimatum game and a GiveSome game in which we attached an LED strip to the frontbottom of a computer monitor and had it display the twolight animations, GL and RH. Specifically, we applied theUltimatum game to study how people’s tolerance regarding
unfair offers changed when the computer showed the twolight animations, and we applied the Give-Some game tosee whether people will behave more cooperative/selfish withrespect to each light animation.
The results are in line with color psychology theories.
The participants perceived the GL light animation positively
and further acted approach-like behaviors by showing higher
tolerance regarding unfair offers and behaving more cooperatively. Similarly, they perceived the RH light animation
negatively and further acted avoidance-like behaviors byshowing lower tolerance regarding unfair offers and behaving
less cooperatively (selfishly). In addition, analysis of thepost-experiment questionnaire showed that the participants
used contrasting descriptions for the two light animations,as listed in Table I. Therefore, the results reveal evidenceof the effect of expressive light animation on both people’s
perception and behavior.
The current results are based on studies taken between
people and a computer. We are now working on installing
an LED lighting system to an iRobot Create 2 robot andgoing to use it as a robotic platform to translate this study
to human-robot interaction scenarios.

TABLE IL IST OF ADJECTIVES USED BY PARTICIPANTS TO DESCRIBE THE LIGHTANIMATIONS .
Green & low intensive

1 Sichao Song is with Department of Informatics, The Graduate University

for Advanced Studies (SOKENDAI), 2-1-2 Hitotsubashi, Chiyoda, Tokyo,
Japan sichaos@nii.ac.jp
2 Seiji Yamada with the National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda, Tokyo, Japan seiji@nii.ac.jp

978-1-5386-2681-8/17/$31.00 ©2017 IEEE2305

Description

friendly, calm, gentle, smiling, beautiful, kind, alive

Red & high intensive
angry, oppressive,
feeling of tension,
warning, challenging, dangerous

No lightanimation
normal