The Butterfly Effect: Novel Opportunities for Steady-State Visually-Evoked Potential Stimuli in Virtual Reality.

In Virtual Reality (VR), Steady-State-Visual Evoked Potentials (SSVEPs) can be used to interact with the virtual environment using brain signals. However, the design of SSVEP-eliciting stimuli often does not match the virtual environment, and thus, disrupts the virtual experience. In this paper, we investigate stimulus designs with varying suitability to blend in virtual environments. Therefore, we created differently-shaped, virtual butterflies. The shapes vary from rectangular wings, over round wings, to a wing shape of a real butterfly. These butterflies elicit SSVEP responses through different animations - flickering or flapping wings. To evaluate our stimuli, we first extracted suitable frequencies for SSVEP responses from the literature. In a first study, we determined three frequencies yielding the best detection accuracy in VR. We used these frequencies in a second study to analyze detection accuracy and appearance ratings using our stimuli designs. Our work contributes insights into the design of SSVEP stimuli that blend into virtual environments and still elicit SSVEP responses.