Psychological Testing for Intellectual Disabilities

While people with learning disorders can be of above-average intelligence, those suffering from intellectual disabilities have a lower-than-average intellect. Learning disorders tend to affect skills like reading, writing, or math, while intellectual disabilities prevent a person from learning and functioning at the same level as others their age^[1].

Psychological assessments are critical in identifying intellectual disabilities and learning disorders. These tests help differentiate between the two conditions to make an accurate diagnosis. Doctors and professionals cannot recommend effective educational plans or support strategies without knowing which issue they are dealing with.

Many different tests are used to assess intellectual disabilities and learning disorders. Each condition requires a complete evaluation, including multiple assessments, to ensure proper diagnosis. In this article, we explore each condition in more detail and uncover the types of tests typically used to diagnose it.

What are Intellectual Disabilities and Learning Disorders?

Intellectual disabilities affect academic and daily functioning, while learning disorders mainly affect academic performance. While both conditions impact cognitive functioning, they do so in different ways.

Intellectual Disabilities (ID)

Intellectual disabilities affect around 1 percent of the population, are typically diagnosed before the age of 18, and are usually identified during childhood. The condition is categorized as mild, moderate, severe, or profound, with most cases (about 85 percent) being mild^[2].

The Merriam-Webster dictionary defines intellectual disability as “mild to severe impairment in intellectual ability.” This means there are general mental limitations affecting adaptive and cognitive functioning^[2].

Adaptive Functioning

Intellectual disabilities affect adaptive functioning (how well a person handles everyday tasks) in three main areas:

• Social skills: The ability to communicate, understand the feelings of others, make friends, and interact socially.
• Practical skills: Self-care, managing responsibilities like work and money, and organizing daily tasks like work or hobbies.
• Conceptual skills: Math, reading, writing, language, problem-solving, memory, and knowledge.

Cognitive Functioning

Cognitive functioning refers to the brain processes allowing people to build knowledge, think effectively and learn new things. It includes memory, attention, problem-solving, reasoning, language, and decision-making skills^[1].

Specific Learning Disorders (SLD)

SLD is a neurodevelopmental disorder that begins during physical development. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) combines three separate learning disorders under the diagnosis of ‘specific learning disorder’ (SLD). To identify the different challenges, it uses three labels^[3]:

• Difficulty with reading (dyslexia)
• Difficulty with writing (dysgraphia)
• Difficulty with math (dyscalculia)

Learning disorders can hinder a person’s academics or career because they cause problems with specific cognitive functioning skills like reading accuracy, spelling, grammar, or calculations. Around 5-15% of school children have learning disabilities, with 80% of these experiencing reading difficulties^[3].

Learning disorders are usually identified when a child begins attending school and (like intellectual disabilities) are classified as mild, moderate, or severe. Support is tailored to individual severity levels. Without treatment, SLD can lead to long-term issues like mental health struggles, unemployment, or dropping out of school^[3].

Learning Disorders and Special Education Services

Under government law (IDEA), students with learning disorders are entitled to special education services, including an evaluation in the event a learning disability is suspected. If diagnosed, an Individualized Education Plan (IEP) is developed to meet individual needs, and schools must provide free and appropriate public education (FAPE) for all students^[3][4]. An IEP may also include related services, such as speech therapy, occupational therapy, and physical therapy if the student is found to have concerns in other functional areas within an academic setting.

Assessing Intellectual Disabilities

Intellectual disability is typically diagnosed using IQ tests, with a score below 70 indicating a possible diagnosis. However, the DSM-5 no longer requires IQ scores to identify intellectual disability but still includes them as part of the description. This ensures IQ scores are considered without being given too much importance in the diagnosis^[2][5][6].

Instead, the IQ score is considered alongside other factors, as it may not fully reflect individual strengths or weaknesses. Therefore, cognitive and adaptive function tests are the primary assessments to diagnose ID. Adaptive functioning assesses daily life skills through standardized tests and interviews with both the individual and those who know them well^[2][9].

Assessing the conceptual, social, and practical areas of adaptive functioning helps professionals understand how intellectual abilities affect daily life. This approach ensures a more accurate diagnosis, essential for creating effective treatment plans and support services^[6].

Cognitive Function Tests

Psychological testing can help assess how well a person can function, especially in terms of thinking and mental abilities. This includes skills like intelligence, attention, processing speed, language, memory, and how well a person understands and processes information. Many tests are used for assessing cognitive function, with an IQ test only being one of them^[8].

Intelligence Quotient (IQ) Test

Intellectual disability is usually diagnosed with an IQ test, which measures a person’s ability to think, learn, and solve problems. While the average IQ is around 100, most people with intellectual disabilities score between 55 and 70, with more severe cases scoring lower^[7].

Wechsler Intelligence Scale for Adults and Children

The Wechsler Intelligence Scale tests measure thinking, problem-solving, and learning abilities, helping identify intellectual disabilities by comparing an individual’s scores to what is expected for their age^[8].

Language and Communication Tests

Language and communication skills are essential for diagnosing intellectual disability because they highlight how cognitive challenges affect daily life and social participation. The following tests can be used to determine this area of cognitive functioning^[8]:

• Boston Naming Test
• Controlled Oral Word Association
• Boston Diagnostic Aphasia Examination
• Clinical Evaluation of Language Fundamentals-4
• Comprehensive Assessment of Spoken Language (for children)
• Test of Written Language (assesses written language samples)

Learning and Memory

Memory functions, like storing and retrieving information, are essential for learning and carrying out daily tasks. In diagnosing intellectual disability, memory difficulties reveal how cognitive challenges affect learning and remembering essential information, impacting functioning in work and social situations. The following tests are commonly used^[8]:

• Wechsler Memory Scale
• Wide Range Assessment of Memory and Learning
• California Verbal Learning Test
• Hopkins Verbal Learning Test-Revised
• Brief Visuospatial Memory Test-Revised
• Rey-Osterrieth Complex Figure Test

Attention and Vigilance

Attention and vigilance involve staying focused and managing distractions while completing tasks. In diagnosing intellectual disability, attention problems show how difficulties with focusing and processing information affect the ability to learn, remember, and complete everyday tasks. The tests below are typically used to assess these functions^[8]:

• Conners Continuous Performance Test
• Test of Variables of Attention
• WAIS-IV Working Memory Index
• Digit Vigilance
• Paced Auditory Serial Addition Test

Processing Speed

Processing speed is how quickly a person responds to questions and handles information, affecting how well they perform everyday tasks. It’s an essential aspect of cognitive function, and delays in processing speed can impact a person’s ability to complete tasks efficiently. The following tests are typically used^[8]:

• WAIS-IV Processing Speed Index
• Trail Making Test Part A

Executive Functioning

Executive functioning involves skills like planning, organizing, decision-making, and multitasking. Impairments in these areas can make it hard to complete complex tasks, make decisions, or focus on multiple things simultaneously. The tests below can be used to assess executive functioning^[8]:

• Trail Making Test Part B
• Wisconsin Card Sorting Test
• Delis-Kaplan Executive Function System

Adaptive Behavior Assessments

Along with assessing cognitive functioning, healthcare professionals will observe adaptive behavior to evaluate how the individual can handle everyday tasks. This includes looking at how well the person interacts with others and takes care of themselves compared to others their age^[5][7].

Adaptive functioning includes three key areas: conceptual skills (like language and learning), social skills (like communication and following rules), and practical skills (like taking care of themselves). This is assessed using standardized tests and input from family, teachers, and caregivers^[5].

While over 200 tools have been identified to measure adaptive behavior, only four have been tested on a broad, representative group of the U.S. population and are designed to help diagnose intellectual disability. These four tools are^[9]:

Vineland Adaptive Behavior Scales 2nd Edition (VABS-II )

This test measures a person’s ability to perform everyday tasks in areas such as communication, daily living skills, and socialization^[9].

Adaptive Behavior Assessment System – II (VABS-II)

The ABAS-II evaluates a person’s skills in the three key areas (conceptual, social, and practical), assessing how well they manage daily activities in real-life situations^[9].

Scales of Independent Behavior-Revised (SIB-R)

The SIB-R assesses an individual’s ability to perform self-care, communication, and socialization tasks by themselves. It helps measure independence and adaptive functioning across different age groups^[9].

Adaptive Behavior Scale-School Version (ABS-S:2)

This tool is used to assess children’s adaptive behavior in school settings, focusing on areas such as academic skills, communication, and behavior management. It helps educators understand how well students can function and interact in school environments^[9].

Specific Learning Disorder Assessments

An evaluation for SLD consists of a medical exam (including neuropsychological evaluation), a developmental and school performance review, a family history discussion, and academic and psychological testing. This comprehensive evaluation reveals if a person has a learning disability and helps create an individualized education plan (IEP)^[11].

Academic Achievement Tests

Academic achievement tests measure a student’s skills in subjects like reading, writing, and mathematics, helping identify problem areas. They also play a key role in diagnosing specific learning disabilities by comparing a student’s performance to age or grade-level expectations, highlighting areas where additional support is needed.

KeyMaths-3 Diagnostic Assessment (KeyMaths-3 DA)

This test evaluates a student’s mathematical abilities, including basic concepts, operations, and problem-solving skills^[10].

Kaufman Test of Educational Achievement, Third Edition (KTEA-3)

The KTEA-3 assesses a wide range of academic skills for students from kindergarten through adulthood, including reading, math, and writing^[10].

Kaufman Test of Educational Achievement, Third Edition Brief Form (KTEA-3 Brief)

A shorter version of the KTEA-3, this test focuses on key academic areas like reading, math, and written expression. It is ideal for quick screening of academic performance^[10].

Wechsler Individual Achievement Test, Third Edition (WIAT-III)

The WIAT-III measures various academic skills, such as reading comprehension, written expression, and mathematics^[10].

Wide Range Achievement Test, Fifth Edition (WRAT5)

The WRAT5 assesses basic academic skills, including reading, spelling, and math computation. It is a quick tool for identifying potential learning challenges in children and adults^[10].

Woodcock Reading Mastery Tests, Third Edition (WRMT-III)

This test evaluates reading skills, including word recognition, comprehension, and fluency. It is commonly used to diagnose reading disabilities, such as dyslexia^[10].

Test of Written Language, Fourth Edition (TOWL-4)

The TOWL-4 measures written language skills, including vocabulary, grammar, and story construction^[10].

Neuropsychological Evaluations

Neuropsychology combines neurology, which studies the nervous system, and psychology, which focuses on the mind and behavior. The nervous system is a complex network of cells and structures that influences the brain, spinal cord, and nerves, controlling everything from basic functions like breathing to more complex actions like thinking, movement, and feeling^[12].

The science of neuropsychology explores how brain and nervous system functions are linked to behavior and cognition, particularly in those with brain damage, mental and learning disorders, or behavioral issues. It includes testing and evaluation to provide accurate diagnoses and treatments^[12].

Neuropsychological testing plays a key role in identifying learning disorders and intellectual disabilities. These specialized evaluations assess how the brain affects behavior and pinpoint cognitive strengths and weaknesses. For example, how well a person’s brain works with thinking, memory, attention, problem-solving, language, and emotional regulation^[13].

Neuropsychological evaluations can also reveal whether a person’s behavior is due to a brain injury or disease. Additionally, these assessments can rule out other mental health conditions that could be causing issues in day-to-day life. These tests are essential in figuring out the best support plan for someone with a learning disorder or intellectual disability.

Interpreting Test Results

Interpreting test results is crucial to diagnosing intellectual disabilities and learning disorders. Intellectual disabilities are diagnosed using a combination of cognitive tests and evaluations of adaptive functioning. This helps determine whether a person’s cognitive abilities are significantly below average, impacting their ability to function in daily life.

In contrast, learning disorders are typically identified through assessments focusing on specific academic skills, such as reading, writing, and math. These tests help pinpoint areas where a person may struggle despite having normal or above-average intelligence. Professionals use a variety of tests to differentiate between intellectual disabilities and learning disorders.

By using these targeted assessments, professionals can accurately diagnose conditions according to DSM-5 criteria, allowing them to recommend optimal educational plans and interventions. These evaluations are key in ensuring individuals receive the necessary support for their unique learning needs.

Key Takeaways

Intellectual disabilities and learning disorders are two separate mental health conditions with different diagnostic criteria in the DSM-5. While people with intellectual disabilities have lower-than-average intelligence and struggle with day-to-day functioning, those with learning disorders are challenged in specific areas such as reading, writing and math.

Numerous tests are used as part of an evaluation to identify strengths and weaknesses, and testing is different for each disorder. If you suspect your loved one is struggling with one of these conditions, it is essential to conduct a complete evaluation to determine how best they can be helped.