It is reported that up to twenty percent of adult learners are neurodiverse. Many are not aware they might have a specific learning difficulty. But what is the science behind testing for learning difficulties?

There is a relationship between overall intelligence, the ability to learn and solve problems, and achievement in academic and formal learning. However, there is a substantial minority who, despite their ability, struggle with formal learning.

Extensive research has been conducted over the past hundred years into the structure of intelligence and cognitive abilities, to understand how people learn and perform at school and in the workplace. Early theories of intelligence suggested a single general factor of intelligence ‘g’ explained the differences between individuals’ abilities. Subsequent research and statistical analysis demonstrated that intelligence can be subdivided into separate but related cognitive abilities, which combine to form an individual’s overall level of cognitive ability.

For the past twenty years, researchers have reached consensus on accepting the Cattel-Horn-Carrol (CHC) model (e.g., Schneider & McGrew, 2012). It offers an explanation of how different cognitive abilities relate to each other, why people differ across the various abilities, and, importantly, how these relate to academic achievement. It is the underpinning model of human cognitive ability used by educational and school psychologists to identify learning disabilities and difficulties.

The CHC model classifies cognitive ability into three hierarchical strata: stratum III a single “general ability” (or g), stratum II consisting of “broad abilities” and stratum I “narrow abilities” (see diagram).

The following broad abilities show significant correlations with academic achievement skills (e.g. McGill et al, 2018):

• Fluid Reasoning (Gf): the ability to reason and solve problems that often involve unfamiliar information or procedures.
• Quantitative Knowledge (Gq): is the ability to comprehend quantitative concepts and relationships and to manipulate numerical symbols.
• Short-Term Memory (Gsm): the ability to hold information in immediate awareness and then use it within a few seconds, also related to working memory.
• Long-Term Retrieval (Glr): the ability to store information and retrieve it later.
• Visual-Spatial Thinking (Gv): spatial orientation, the ability to analyse and think with visual information, including the ability to hold and manipulate mental images.
• Processing Speed (Gs): the speed and efficiency in performing automatic or very simple cognitive tasks.
• Auditory Processing (Ga): the ability to discriminate, analyse, and synthesise auditory information.
• Comprehension-Knowledge (Gc): the breadth and depth of knowledge including verbal communication and information – otherwise known as crystallised intelligence.
• Reading Ability (Gr): includes basic reading skills.

Additionally, the model includes other broad abilities including:

• Olfactory: ability to detect and process information in odours.
• Tactile: ability to process information from touch sensations.
• Psychomotor: ability to perform body motor functions with precision or strength.
• Kinaesthetic: ability to detect and process information relating to limb position and movement.