  Understanding the relationship between the decoding accuracy of a
brain-computer interface (BCI) and a subject's subjective feeling of control is
important for determining a lower limit on decoding accuracy for a BCI that is
to be deployed outside a laboratory environment. We investigated this
relationship by systematically varying the level of control in a simulated BCI
task. We find that a binary decoding accuracy of 65% is required for users to
report more often than not that they are feeling in control of the system.
Decoding accuracies above 75%, on the other hand, added little in terms of the
level of perceived control. We further find that the probability of perceived
control does not only depend on the actual decoding accuracy, but is also in
influenced by whether subjects successfully complete the given task in the
allotted time frame.
