Persons using SCIT ('participants') are briefly shown a pair of lines on a computer screen and asked to indicate which side is the shortest by pressing a keyboard button. This process is repeated many times while we record their speed of response and the number of errors made. Most people can complete SCIT within 3-4 minutes.
The 'H' version of SCIT is used to test high-functioning adults, while the easier 'U' version is used for children and people with known cognitive impairment.
SCIT is sensitive to small changes in the speed of signal processing and in the effectiveness of signal processing, within subcortical and cortical pathways of the brain. SCIT can detect changes before they begin to noticeably affect an individual’s performance on everyday tasks.
Impaired SCIT performance indicates that some of the neural networks were not functioning properly at the time the test was conducted. It does not indicate the reason for the impaired performance. In other words, it is a screening test, not a diagnostic test.
SCIT has its origins in the ‘Inspection Time Task’ that has been used by psychologists since the 1970’s. The test has been refined in a number of significant ways to make SCIT much quicker and more sensitive than the inspection time task.
SCIT is one of the rare cognitive tests not influenced by practice, so it can be used to repeatedly test someone over a short period of time. This property makes SCIT useful for detecting the short-term effects of drugs or medications on cognition.
Most cognitively normal individuals display stable SCIT performance so that similar results are obtained when a person is retested months or even years later. This property makes SCIT useful for detecting decrements or improvements in cognition, such as happens in neurodegenerative diseases or after therapeutic interventions.
Factors that DO NOT influence performance on SCIT
Sex Provided that they are cognitively normal at the time of testing, both sexes perform equally well on SCIT.
Experience Unlike most other cognitive tests, performance on SCIT is not influenced by practice (the test-retest reliability is approximately 0.95), so SCIT can be used to test a participant repeatedly over a short period of time.
Emotional state Performance on SCIT is not influenced by mild or moderate mood states (anxiety, stress or depression). However, like all cognitive tests, performance on SCIT is affected by severe mood states.
Level of education Provided that age and IQ are accounted for, a participant's educational status does not affect their performance on SCIT.
Factors that CAN influence performance on SCIT
Visual impairment People with cataracts or other forms of visual impairment perform poorly on SCIT. Participants with myopia or other correctable visual disorders can perform normally if they wear their contact lenses or spectacles.
Age Performance on SCIT gradually declines with age, but this change can be controlled for by using population norms or by comparing to data obtained from prior tests by the same participant.
Language skills Participants who lack a working knowledge of English can have difficulty understanding the written instructions for SCIT, and should not be tested unless a translator is available.
Intoxication Performance on SCIT can be impaired in individuals with a blood alcohol concentration of 0.05 or higher. It is likely that other recreational, prescribed or elicit drugs will affect performance on SCIT.
Sleepiness It is preferable to test individuals on SCIT when they feel rested and alert. Individuals with jetlag or acute sleep deprivation show impaired performance on SCIT. General tiredness does not affect performance.
Mild cognitive impairment Individuals with mild-moderate cognitive impairment (with an MMSE score of 24 or less) find SCIT difficult and are often unable to complete the test.
Movement disorders Individuals with severe osteoarthritis or Parkinsonian symptoms can find it difficult to press the keyboard buttons, which slows their recorded response times.
Systemic inflammation Individuals with untreated coeliac disease or Crohn's disease perform worse than healthy peers on SCIT. It is possible that other disorders involving systemic inflammation are also associated with impaired performance.