Symbol Span asks the person to remember designs and where they appeared
Symbol Span shows the person visual designs in relative positions; after seeing them, the person identifies which designs appeared and where they were located.
Symbol Span is a secondary subtest of the WAIS-5 Working Memory Index, or WMI. Together with Spatial Addition, it contributes to the Visual Working Memory Index. It was added in WAIS-5; WAIS-IV and WAIS-5 compared explains the wider change.
What higher and lower Symbol Span performance can show
Symbol Span draws on several related working-memory processes:
- forming a distinct mental image of each design;
- encoding its relative position on the page;
- keeping each design paired with the correct position until the response.
Higher performance shows that the person remembered both the designs and their relative positions accurately. Lower performance can take several forms: a shape may be retained while its location is lost, the locations may be retained while the design-position pairs become confused, or both parts may become difficult to maintain. The result provides focused evidence about visual working memory, or Gwm.
The same demand appears when remembering which item occupied each position in a visual layout.
Symbol Span differs from Spatial Addition and auditory working-memory tasks
| Subtest | Information format | Central task demand |
|---|---|---|
| Symbol Span | Designs and their relative locations | Retain the appearance of each design together with where it appeared |
| Spatial Addition | Visuospatial information | Retain and combine several pieces of spatial information while filtering competing input |
| Running Digits | Spoken digits | Keep recent auditory information current as input continues |
| Digit Sequencing | Spoken digits | Retain a completed set and rearrange it into numerical order |
Symbol Span emphasises storing the designs and their locations. Spatial Addition places greater emphasis on manipulating several pieces of visuospatial information and filtering competing input, while Running Digits and Digit Sequencing work with auditory numerical material.
A relatively higher Symbol Span result than Spatial Addition can indicate that remembering design-location pairs was easier than combining and filtering spatial information. A higher result than the auditory tasks can indicate stronger visual design-and-location memory than auditory working memory. How to read WAIS results explains how to interpret these differences within the wider profile.
BrainTypeIQ Visual Reversal uses a visual sequence instead
BrainTypeIQ Visual Reversal uses another visual working-memory format: visually presented locations must be retained as a sequence and reproduced in reverse order. This gives BrainTypeIQ a focused measure of visual-sequence storage and manipulation within its five-domain cognitive profile.