implementing security access includes receiving a request to perform an activity over a network and administering a cognitive test responsive to the request . the administering includes randomly selecting a set of related images from a database of images , randomly selecting one image that is unrelated to the set of related images , displaying the set of related images along with the image that is unrelated to the set of related images , and prompting a user to identify the image that is unrelated to the set of related images . implementing the security access also includes processing results of the cognitive test , and executing the activity when it is determined from the processing that the cognitive test has been successfully completed .