The Bottleneck of Thought
Working memory is the cognitive workspace where we hold information temporarily while reasoning, comprehending language, or solving problems. Its limited capacity — famously described by George Miller as 'the magical number seven, plus or minus two' — represents one of the most fundamental constraints on human cognition. This simulation models how chunk size, rehearsal speed, and trace decay interact to determine how much you can hold in mind at once.
Chunking and Capacity
Chunking groups individual items into meaningful units, effectively expanding capacity. A chess grandmaster sees board positions as familiar patterns (chunks) rather than individual pieces, enabling recall of entire game states. The parameter k controls chunk size: larger chunks mean more information per slot, but each chunk still occupies one capacity unit.
The Rehearsal Loop
Baddeley's phonological loop model explains how we maintain verbal information through subvocal repetition. The rehearsal rate R determines how quickly items can be refreshed before their traces decay with time constant τ. When rehearsal is blocked (articulatory suppression), capacity drops dramatically — evidence that active maintenance is essential, not merely passive storage.
Attention as a Bottleneck
Working memory and attention are deeply intertwined. The attention load parameter A simulates dual-task conditions where cognitive resources must be shared. High load leaves fewer resources for memory maintenance, causing items to drop out of the active buffer. This interaction explains why distracted driving is dangerous and why multitasking degrades performance on all concurrent tasks.