Corsi Block-Tapping

01Origins

In 1971, neuropsychologist Brenda Milner first reported a way to probe memory through spatial locations; a year later her doctoral student Philip Corsi standardized it in his McGill University thesis — and the paradigm has carried his name ever since.

Its purpose was to build a non-verbal, spatial counterpart to the classic digit span: if recalling a string of digits taxes language, then recalling a string of locations should tax space.

02How it works

Nine identical blocks sit scattered irregularly on a board, numbered only on the examiner's side. The examiner taps a sequence at about one block per second, and you must tap it back in the same order.

Sequences start at two blocks and grow. The longest sequence you can reproduce correctly is your Corsi span. A backward variant, asking for reverse order, loads mental manipulation more heavily.

03What it measures

Corsi indexes the capacity of visuospatial short-term and working memory. In Baddeley's model it loads chiefly on the visuospatial sketchpad, separate from the verbal phonological loop; beyond three or four items it also recruits the central executive to keep order.

04Where the brain works

Imaging and lesion work converge on a predominantly right-hemisphere fronto-parietal network: right posterior parietal cortex and the intraparietal sulcus hold spatial locations, the right dorsolateral prefrontal cortex handles order and control, and the medial temporal lobe (hippocampus) supports spatial-sequence memory. Kessels et al. (2000) found right-hemisphere patients performed markedly worse.

05Key findings

Healthy adults score a Corsi span of about 5 to 6 — reliably lower than the digit span (~7±2). Spatial sequences can't be silently rehearsed the way digits can, which makes them harder.

Crucially, verbal and spatial spans can doubly dissociate: some patients lose digit span while spatial span is intact, and others the reverse — strong evidence that verbal and spatial memory are two relatively independent systems in the brain.

06Where it's used

As a gold standard for visuospatial working memory, Corsi is widely used in neuropsychological assessment — Alzheimer's disease, mild cognitive impairment, stroke and traumatic brain injury — and in developmental and cognitive-aging research to trace this ability from childhood into old age.