“Valence” (Tom De Smedt, Lieven Menschaert & Ludivine Lechat, 2011) is an interactive installation that represents the player's affect (relaxation or arousal) by measuring alpha brain waves, using a wireless EEG headset. The headset prototype is developed by Imec (BE) and Holst Centre (NL). It consists of eight dry electrodes and a wireless broadcaster. A mobile system for measuring EEG signals (electro-encefalorgram signals or commonly brain waves) is useful in healthcare applications, for example, it can be used to monitor epileptic patients during their daily activities, and to issue a warning when they are about to have an epilepsy attack. We use the EEG headset in an artistic context.

Alpha brain waves increase when we relax, and the brain hemispheres (left/right) play a role in the processing of emotions. According to the valence hypothesis, the left brain hemisphere is dominant when processing positive emotions, and the right brain hemisphere is more active when processing negative emotions. Our installation explores this hypothesis.

Valence exhibited at Creativity World Forum 2010. Photography © Ludivine Lechat.

Using NodeBox for OpenGL, we developed a game environment that interprets the alpha and valence state of your brain. As demonstrated in the figure below, high alpha (relaxation) will make the particles that float around on the screen attract, to form a sticky ball at the center of the screen. A drop in alpha brain waves makes the particles repulse from each other. High valence (arousal) produces colorful and eccentric particles.

In a follow-up project, we collaborated with electronics engineer Tim Augustynen, to expand our setup with ambient lighting. We used a home automation server to control the lighting's intensity based on the player's affect. The lights in this video are produced by MGX using 3D printing.

For further information, see the references or watch Julien Penders' talk at Creativity World Forum 2010 (on YouTube).


Tom De Smedt * game development EMRG
Lieven Menschaert game development EMRG
Ludivine Lechat game artwork
Tim Augustynen ambient lighting
Bernard Grundlehner EEG analysis Holst Centre
Michel Noorloos EEG analysis Holst Centre
Julien Penders project coordinator Holst Centre
Imke Debecker project coordinator Imec


Tom De Smedt (2013). Modeling Creativity: Case Studies in Python. University Press Antwerp. ISBN 978-90-5718-260-0.
Tom De Smedt & Lieven Menschaert (2012). VALENCE: Affective visualisation using EEG. Digital Creativity, 23(3-4): 272-277.
Tom De Smedt, Ludivine Lechat & Walter Daelemans (2012). Generative art inspired by nature, in NodeBox. In Di Chio, Cecilia (ed.) Applications of Evolutionary Computation, Part II, LNCS 6625: 264–272. Berlin: Springer.

Wireless EEG headset