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.
In WAIS-IV, Letter-Number Sequencing is a supplemental subtest of the Working Memory Index, or WMI. In WAIS-5, it remains secondary and contributes to the Expanded Working Memory and Auditory Working Memory–Manipulation ancillary indexes, rather than primary WMI or FSIQ. WAIS-IV and WAIS-5 compared explains the wider change in subtest and index structure.
The person must use working memory (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.
In WAIS-IV, the Sequencing condition within Digit Span requires one type of information—numbers—to be reordered; in WAIS-5, Digit Sequencing is a separate subtest. 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
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.
- 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.
Outside the assessment, writing numbers and letters into separate groups makes the categories visible, so retention, classification, and ordering do not all have to happen at the same time.
How to read WAIS results explains how to place the subtest score alongside the relevant index scores, other subtests, and behaviour during testing.
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 manipulation, so the distinction is not “retention versus manipulation.” Letter-Number Sequencing uniquely requires mixed information to be classified into two types before each type is ordered.
BrainTypeIQ Computation Span contrasts calculation with classification and ordering
BrainTypeIQ Computation Span also combines processing with retention. Letter-Number Sequencing classifies mixed numbers and letters and orders each category, whereas Computation Span requires calculation while the results are retained for later recall. Both show how performance changes when information must remain available during another mental operation.