According to certain embodiments, an authentication system comprises memory operable to store instructions and processing circuitry operable to execute the instructions, whereby the authentication system is operable to provide a stimulus that causes an involuntary facial movement of a user. The authentication system is further operable to receive user data in response to the stimulus. The user data depicts the involuntary facial movement of the user. The authentication system is further operable to perform authentication based on comparing the user data to validation data associated with the user. The validation data comprises a previously validated depiction of the involuntary facial movement caused by exposing the user to the stimulus.