SlowcoachBorderline intellectual functioning cannot be defined by an IQ of 70-85 alone. This range is an important clue, but measurement error, adaptive functioning, developmental history, and everyday context also need consideration.[1][2]
In the first article, I explained that the figure of “approximately 7 million people with borderline intellectual functioning” was not a count of people who had actually been diagnosed. After finishing that article, a natural next question remained: “Then who is considered to have borderline intellectual functioning?”
1. Where did the IQ range of 70-85 come from?
Borderline intellectual functioning has long been described in relation to intellectual functioning 1-2 standard deviations below the mean. Sources give slightly different boundaries, such as IQ 70-85 or 71-84.[1][2]
The earlier DSM-IV-TR specified a range of 71-84. This makes it easy, even today, to treat the numbers as firm dividing lines: “An IQ in the high 70s means borderline intellectual functioning” or “Above 85 means it is not.”[1]
However, intelligence-test scores have measurement error. They can also be affected by health, anxiety, concentration at the time of testing, educational experience, language, and culture.[1][2]
There is no wall between 84 and 85 that divides people's lives.
2. Why did DSM-5 remove the numerical criterion?
DSM-5 and DSM-5-TR no longer specify the earlier operational range of 71-84. Borderline intellectual functioning remains a condition that may require clinical attention rather than a standalone disorder diagnosis.[1][2]
What DSM-5 removed was the previously explicit IQ boundary, not borderline intellectual functioning itself.[1][2]
Different sources explain this differently, which confused me at first as well. Borderline intellectual functioning did not suddenly cease to be a disorder in DSM-5. It was not a standalone disorder diagnosis in the DSM-IV era either. The actual change was the removal of the numerical boundary.[1]
Some have criticized this removal for making it less clear how borderline intellectual functioning should be identified.[1] That does not mean IQ is disregarded. It is closer to saying that the score should be considered alongside adaptive functioning, developmental history, and everyday context.[2]
3. The same score can accompany different difficulties
Imagine two people with the same IQ score.
One may miss information in spoken explanations but understand well when shown pictures or a demonstration. The other may understand the content but have greater difficulty remembering the order of tasks or maintaining attention.
Even with the same IQ score, the points of difficulty and the support needed can differ.[2][3]
A 2025 systematic review described varied patterns of difficulty among people with borderline intellectual functioning across executive functioning, working memory, cognitive flexibility, processing speed, planning, and language-related abilities.[3]
This makes it difficult to sum everyone up with a statement such as “People with borderline intellectual functioning are like this.” Similar overall scores can accompany different cognitive profiles.[3]
4. Is it true that there are four types?
I also examined a study of cognitive profiles directly. Jankowska and colleagues used cluster analysis of WISC-R results from 114 Polish students and identified four cognitive profiles.[4]
- A profile with weaker verbal abilities but relatively stronger visuospatial abilities
- A profile with particular weaknesses in short-term memory and attention
- An ACID-pattern profile, also observed in some learning disabilities
- A profile with no clear relative strengths on the test and generally low performance across several areas
These findings illustrate how very different strengths and difficulties can exist under the same label.
However, it would be a mistake to treat these four profiles as official types.
The four profiles identified in one study should not be applied directly to everyone with borderline intellectual functioning.[3][4]
This was a cluster analysis based on 114 Polish students and the WISC-R. It is not an internationally agreed official classification into four types. Different ages, cultures, assessment tools, and analytical methods could produce different findings.[3][4]
5. What should we consider alongside the score?
Following the evidence made me feel that we need to change the question a little.
Rather than stopping at “What is the IQ score?”, we should also ask:
- Which does the person understand better: a long explanation or a short demonstration?
- Can they remember the sequence of tasks, or do they need an external checklist?
- How do they respond to unexpected changes?
- What can they do independently, and what can they do with assistance?
- How do repeated failures show up in learning, relationships, and working life?
These questions are not intended to create another classification of people. They are intended to identify where someone actually gets stuck and what kind of help might work.
For example, visual materials and direct demonstrations may be a better fit for someone who finds verbal explanations difficult. Short instructions broken into steps, checklists, and repeated checks may help someone who has difficulty with working memory and attention.
When we explain a person through a single score, we miss both their strengths and ways to support them.
6. What to be especially careful about when judging for yourself
Reading about the characteristics of borderline intellectual functioning may lead you to think, “That sounds like me,” or to think of someone you know. However, difficulty with learning or working life alone does not establish borderline intellectual functioning as the cause.
Several factors can produce similar difficulties, including attention problems, anxiety and depression, and learning experiences. A formal assessment needs to consider developmental history and functioning in everyday life alongside standardized intelligence testing.[2]
We should not conclude that we or someone else has borderline intellectual functioning based only on an online test result or a few characteristics.
Assessment should be a process for understanding support needs more accurately, rather than a procedure for labeling people.
Slowcoach aims to identify the points where people repeatedly get stuck in actual work and connect them with explanations, manuals, practice, and human support that fit their needs, rather than focusing on IQ scores themselves.