Unadze illusion fixed set test

From Luria's book Neuropsychology of  Memory

Unadze DN.  Experimental psychological investigations.  Moscow.  Nauka.  1966.

A subject is given 2 balls of different sizes to squeeze (one per hand) 10-15 times for several seconds per squeeze.  He compares their sizes and reports his finding.  Then, without visual inspection he is given 2 balls of equal size and asked to compare the sizes.  The result is that the hand that held the larger ball now reports it is holding a smaller ball, and is maintained even after 12-18 trials.

Luria's variation was to test normal, mildly and severely impaired subjects on the test.  He found that in severely amnesic subjects only, and only with interference, the fixed set effect was achieved but rapidly forgotten, underlying the importance in interference on somatic memory. Pauses less than 2 minutes had little effect on retention, as with other types of learning.