"Synapses can't be stronger than that," he said. "The brain is a very complex biochemical machine."
Mathematical models like these may seem removed from the gritty reality of gray matter and neural chemistry, according to Karl Friston, who directs the Wellcome Trust Centre for Neuroimaging at University College London, but they provide a critical connection between what people actually experience and the hidden mechanisms inside the brain.
Rabinovich's model, Friston said, "is both plausible and compelling." It correctly predicts the working memory's capacity and with a little elaboration could be tested experimentally. Friston said the model suggests patterns in the working memory's activity that should be discernible in the brain's electrical signals.
The exception to Rabinovich's model may be people with autism who skip effortlessly past seven and eight items, memorizing even a hundred random numbers in a single read-through. Their brains seem to be able to create much stronger pathways than the typical brain.