: I really don’t know how IQ tests work, Please someone explain on what basis someone’s IQ is judged?
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Hey, great question! When a registered psychologist or allied health professional uses a comprehensive cognitive assessment, they are measuring a person’s ability to respond to queries and complete certain tasks. That person’s scores are then compared to other people their age who completed the same tasks when the test was first having the data for its norms collected. You either score above or below your same age peers, and depending on how much higher or lower, and in what area/s, that may tell the psych something useful and allow them to share good strategies with you for working to your strengths and working to understand areas if a difficulty/difference is found.
The cognitive areas measured are usually:
Verbal comprehension (can you think outside the box and articulate your thoughts and ideas?)
Visual spatial ability (can you get hands on with visual problems/mental rotation tasks and solve them under time pressure?)
Fluid reasoning (can you identify and solve visual patterns?)
Working memory (can you listen to and look at sets of numbers/letters/pictures, hold it in mind and recall them as required?)
Processing speed (can you learn and complete a new visual processing task under time pressure?)
Full Scale Intelligence Quotient (FSIQ, or even just IQ for short) is then measured as a result of your performance in a few tasks across the above areas.
Without getting bogged down in how we calculate all the stats, the FSIQ score is a standard score with mean of 100 and standard deviation (SD) of 15 on a normal distribution (also called a bell curve). If we think of a nice bell curve with a mean of 100 and then consider the score we get, we can check how far from 100 it is in groups of 15. The further away from 100, the further above or below expectations.
If Romi gets a FSIQ of 117 on a cognitive assessment, that means they scored above the mean (100), and more than one SD above the mean (115), but not quite two SDs above the mean (130). When you convert to a percentile rank, that says Romi scored at or above 87 percent of their same age peers on the same test. Great work Romi! There may be some huge cognitive areas of strength and some areas of difficulty and that’s for the psych to chat through with you.
If Alex gets a FSIQ of 67, that means they scored below the mean (100), more than one SD below (85), and even more than another SD below (70). When you convert to a percentile rank, that says Alex scored at or above 1 percent of their same age peers. That’s really really low and may be indicating an intellectual disability. The psych will also then explore other areas like developmental history, medical history, adaptive behaviour, interviews, observations, discussions with family/other stakeholders to check whether Alex fits diagnostic criteria for an intellectual disability, and advise next steps from there.
There are a lot of criticisms of cognitive assessments – one of the main ones being that we are ‘mostly’ defining intelligence as the white, western notions of cognition in the research and we may not be doing our best to explore cognition across diverse cultural groups. Verbal skills in English may not be the best contributor to an intelligence measuring test for an indigenous and/or non-english speaking person.
Anyway hope it helps.
Source: am registered psych and teach stats to special educators in Aussie.
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