A global learning disability is partially defined by a significant, life-long impairment in a number of areas of cognitive functioning, including

• the person’s understanding of words (verbal skills)
• numbers (abstract conceptual skills) and pictures (visual-spatial skills)
• their memory and processing speed

Cognitive functioning is usually assessed through gathering information about a person’s educational achievements at the initial screening stage and through direct observations at the ICA stage.

If it has not been possible to gather sufficient information to make a decision at these stages, we can do a further assessment of a person’s cognitive functioning using standardised measures of ‘intelligence’. The assessment that is used most often is the Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV), which measures four domains

• visual skills
• verbal skills
• working memory
• processing speed.

Scores on different domains of the WAIS-IV can produce a Full-Scale IQ score. A global learning disability is partially defined by a Full Scale IQ score of 69 or below. However, it is important to note that there are many instances in which it would not be appropriate to conduct a cognitive assessment: due to sensory or physical impairments, language barriers, and when a person would not be able to give their ‘full effort’ (e.g. due to mental health problems or while experiencing an acute period of distress associated with difficult life events).

There are many reasons why scores on cognitive assessments may not be a valid representation of the person’s ‘true’ cognitive abilities. There are also many instances in which a Full Scale IQ score may not be valid and so cannot or should not be reported, for example if a person has not completed all core subtests of the WAIS-IV or there is significant variation in their scores across the subtests. CLDS therefore only completes cognitive assessment in exceptional circumstances.