What is the Wechsler Preschool and Primary Scale of Intelligence?

The Wechsler Preschool and Primary Scale of Intelligence(WPPSI-R) is a standardized assessment aimed to measure the cognitive development for children ages 2.6 to 7.7 years. This assessment is currently in its fourth edition. There are three levels of interpretation which are: full scale, primary index scale, and ancillary index scale. This test consists of several subtests, each of which is aimed at assessing specific intellectual abilities. The results allow professionals and parents to see what areas their children excel in and what areas are more challenging so that instruction can take place in ways that allow them to be the most successful.

The primary index scale is composed of subtests which evaluate verbal comprehension, visual-spatial skills, working memory, fluid reasoning and processing speed. The child’s abilities are determined by tasks that the children perform. The following show the areas that are assessed with their associated tasks:

  • Verbal comprehension: Information similarities
  • Visual-spatial: Block design, object assembly
  • Fluid Reasoning: Matrix reasoning, picture concepts
  • Working memory: Picture memory, zoo locations
  • Processing speed: Bug search, cancellation

The ancillary scale includes assessments for vocabulary acquisition, nonverbal skills, general ability and cognitive proficiency skills. The areas and their associated tasks are below:

  • Vocabulary acquisition: Receptive vocabulary, picture naming
  • Nonverbal: Block design, object assembly, matrix reasoning, picture concepts, pic
    picture memory, zoo locations, bug search, cancellation, animal coding
  • General ability: Information similarities, vocabulary comprehension, block
    design, object assembly, matrix reasoning, picture concepts
  • Cognitive proficiency: Picture memory, zoo locations, bug search, cancellation,
    animal coding

The full-scale test uses all of the subtests and tasks to derive one overall intelligence or IQ score.

Children receive a score for each of the subtests and a score for overall intellectual ability. Each subtest provides a scores from 1 to 19 with scores between 7 and 12 being average. Additionally, a percentile rank is provided for each area. This score indicates how the child did compared to other children of the same age. This would be reported as PR = 25, which means that the child scored as well or better than 25% of children the same age. The average for the overall intelligence is a score between 90 and 100. Sores are determined by the child’s ability to give right or wrong answers. While some tasks involve answering questions posed by the examiner, other tests require the manipulation of objects to demonstrate a correct response such as copying a pattern with blocks.

The results of the WPPSI-R are considered to be reliable at a 95% confidence interval which means that there is a 95% certainty that the results are true and accurate. A trained professional follows an established protocol when giving the assessment to ensure that the results are valid and reliable. This includes a period of time to ensure that the child is comfortable with the examiner before the test begins. It may also mean that the testing session is spread over multiple days, typically two, to ensure the child is performing their best and not getting overwhelmed or tired. Overall, this assessment is the most widely accepted by professionals when it comes to evaluating the intellect of young children.