Letter-Number Sequencing is a supplemental task that requires two types of information to be reordered
WAIS Letter-Number Sequencing presents a mixed spoken sequence of numbers and letters. The person must separate the two types of information, reorder each according to the stated rule, and give the reorganized sequence aloud. The Japanese version uses kana speech sounds in place of letters.
In the Japanese WAIS-IV, Letter-Number Sequencing is a supplemental subtest of the Working Memory Index, or WMI for ages 16:0 to 69:11. The standard WMI in that edition is calculated from the core subtests Digit Span and Arithmetic. Letter-Number Sequencing provides a closer look at the ability to organize mixed auditory information.
The task combines retention, classification, and reordering
Letter-Number Sequencing requires the person to use working memory, or Gwm, to reorganize what they heard before responding:
- listen to a mixed sequence of numbers and letters;
- retain the complete sequence briefly;
- separate the numbers from the letters;
- place each type of information in the required order; and
- say the reorganized sequence aloud.
Digit Sequencing within Digit Span requires one type of information—numbers—to be reordered. Letter-Number Sequencing adds classification into two types. Listening, attention, retention, classification, and reordering must therefore be coordinated throughout the task.
What higher and lower Letter-Number Sequencing scores can show
In the Japanese WAIS-IV, a higher scaled score indicates that, compared with people of the same age, the person could retain mixed auditory information accurately, separate its two types, and reorganize each according to the rule. They handled the combined demand of remembering the information while classifying and sequencing it.
When the score is lower, responses during the assessment can help identify where the process became more demanding. How to read WAIS results explains how to place the scaled score alongside WMI and the other subtests.
- Numbers or letters are missed while the sequence is being heard.
- Individual elements are heard, but the full sequence is difficult to retain.
- The two types of information become confused while being separated.
- The information is classified correctly, but reordering within each type is difficult.
Everyday tasks can create a related demand when several pieces of spoken symbolic information must be retained briefly and organized according to fixed classification and sequencing rules. Writing the information down in separate groups removes the need to retain, classify, and reorder everything entirely in the mind.
How Letter-Number Sequencing differs from Digit Span and Arithmetic
| Subtest | Main material | Direct task |
|---|---|---|
| Digit Span | Numbers | Reproduce numbers in the original, reverse, or ascending order |
| Arithmetic | Problems involving quantitative relationships | Retain the conditions, select an operation, and calculate mentally |
| Letter-Number Sequencing | Numbers and letters | Separate two types of information and place each in the required order |
Digit Span also includes Backward and Sequencing conditions, so it would be misleading to describe Digit Span as retention and Letter-Number Sequencing as manipulation. The distinctive feature of Letter-Number Sequencing is that mixed information must first be classified into two types and then ordered within each type.
Letter-Number Sequencing remains a secondary subtest in the 2024 US WAIS-5
In the 2024 US WAIS-5, Letter-Number Sequencing remains a secondary subtest. Digit Sequencing and Running Digits are the primary subtests of the standard WMI, while Letter-Number Sequencing is not part of the standard WMI and is not one of the seven subtests used to calculate FSIQ.
Within that US edition, Letter-Number Sequencing is included in the Expanded Working Memory and Auditory Working Memory–Manipulation ancillary indexes. Although it is not a primary subtest, it retains a specific role in examining the classification and reordering of mixed auditory information. WAIS-IV and WAIS-5 compared summarizes the wider changes to indexes and subtests.