short-term memory is a passive buffer that holds information briefly (seconds).
working memory (a newer concept) includes active manipulation (reasoning, combining, transforming what’s held).
The workspace can hold ~4 chunks simultaneously.
This seems to be the core bottleneck for active cognition.
The only way to increase effective capacity is to encode more bits per chunk.
In the brain, there are “silent synapses” which can be quickly turned from off to on for quick learning.