What is Processing Speed?
When describing Processing Speed in my reports, I write:
Processing Speed measures the speed and accuracy of visual identification, decision making, and decision implementation.
There are three key components of this statement: 1) visual identification, 2) decision making, and 3) decision implementation. Simply put, processing speed involves the ability to identify the task at hand, recognize the decision that needs to be made, and make the decision.
Students who excel at processing speed are able to work quickly on cognitive and academic tasks. Usually they are among the first students to finish a test or to complete homework assignments. Determining a student’s processing speed gives us insight into how efficiently he or she is able to complete such tasks. As we’ll see below, however, students who work quickly may also experience other variables that contribute to their speed, some that aren’t necessarily positive.
How is it Calculated?
The Processing Speed index score is calculated using two subtests: Coding and Symbol Search. This is true for both the WISC-V (for children and adolescents) and the WAIS-IV (for adults).
The Coding subtest requires the student to view a series of numbers written in rows on a page. The student then draws a corresponding symbol under each number. The student is given two minutes to complete as many symbols as possible. The student is awarded one point for each correctly drawn symbol. The student is not penalized for incorrect symbols.
The Symbol Search subtest displays one or two symbols (depending on the age of the student) on the left hand side of the page. The student then must determine whether that symbol appears in a series of symbols displayed on the right side of the page. If the symbol appears, the student circles it. If not, the student checks the “No” box. The student has two minutes to complete as many items as possible. The student is then awarded one point for each correct answer but loses a point for each incorrect answer.
Once the two subtests are completed and scored, the score is then converted to a standard score that can be interpreted. The Processing Speed index score can be interpreted using the following scale:
- 130 or above: Very Superior
- 120-129: Superior
- 110-119: High Average
- 90-109: Average
- 80-89: Low Average
- 70-79: Borderline
- Below 70: Extremely Low