Inhibitory control test is a simple test measuring the person's attention. It is proposed as one of the ways to help in the diagnosis of early stage of hepatic encephalopathy. The person taking the test is presented with random sequence of letters, among which he should discern interchanging X's and Y's and press the button when either of these two letters follows the other. Button should be pressed even when the first target letter is not followed by the second directly, being interspread with random non-target letters. Sometimes two similar target letters come in succession, luring the person into false reaction. Effective inhibition of such automatic erroneous reaction supposedly gives evidence of good brain function, while failure to keep 'lure' errors at low level points at possible mild dysfunction. The cause of the dysfunction could be the underlying liver problem that has not yet manifested in acute physiological symptoms.