Sequence reasoning skills

Sequence reasoning is inferring the rule that generates a series of numbers, letters or figures and applying it to predict the next item. Most sequences are built from a small set of rule types: constant differences, multiplication, alternating patterns, combined operations or position changes. Solving them reliably depends on checking differences systematically rather than guessing.

First, calculate the differences between consecutive items. If they're constant, you've found the rule. If not, calculate the differences of the differences, or check ratios. If nothing fits, split the sequence into odd and even positions to test for two interleaved series. For figure sequences, list each feature separately, such as rotation, count and shading, and track each one across the series.

Sequences place heavy demands on working memory because you must keep earlier items and candidate rules active while calculating. Under time pressure, people tend to test the most familiar rule first and stop if it almost works. Alternating sequences cause many errors because the brain expects one continuous pattern.