Answer: The Corsi block-tapping test is a human behavioral test that measures short-term memory with non-verbal stimuli.
In the Corsi test, the subject is presented with nine blocks. The experimenter will then tap a number of blocks in sequence, usually starting with three blocks. The subject then mimics the pattern of block tapping. After successful, a new, longer pattern of blocks will be tapped in sequence. The highest successful recall streak is called the Corsi span.
The Corsi block-tapping test is a measure of visual short term memory. The average person would be able to successfully remember a pattern of about 6 blocks in order.
Patient HM, with his significant anterograde amnesia, could not successfully tap more than 5 in a row. HM’s results on the Corsi block-tapping test were described by Suzanne Corkin in her book, Permanent Present Tense. Deficits in the Corsi block tapping test have also been observed in frontotemporal dementia, Alzheimer’s disease (Memory impairment differs in frontotemporal dementia, Alzheimer's disease.), and early Parkinson’s disease (Deficits on Corsi's block-tapping task in early stage Parkinson's disease.)
You can read the primary research concerning the Corsi block tapping test here: