  In this paper we introduce the combined use of Brain-Computer Interfaces
(BCI) and Haptic interfaces. We propose to adapt haptic guides based on the
mental activity measured by a BCI system. This novel approach is illustrated
within a proof-of-concept system: haptic guides are toggled during a
path-following task thanks to a mental workload index provided by a BCI. The
aim of this system is to provide haptic assistance only when the user's brain
activity reflects a high mental workload. A user study conducted with 8
participants shows that our proof-of-concept is operational and exploitable.
Results show that activation of haptic guides occurs in the most difficult part
of the path-following task. Moreover it allows to increase task performance by
53% by activating assistance only 59% of the time. Taken together, these
results suggest that BCI could be used to determine when the user needs
assistance during haptic interaction and to enable haptic guides accordingly.
