Ericsson and Pool (2016) use the term “mental representations” as vernacular shorthand for the chunking schema (“Chunks” in human cognition) a person uses in some domain (Efficient chunk schemas usually encode domain-specific attributes).
Mental representations matter because information processing capacity varies with their complexity. Human channel capacity increases with stimulus dimensionality and Human channel capacity increases with bits-per-chunk.
… mental representations … make it possible to process large amounts of information quickly, despite the limitations of short-term memory … one could define a mental representation as a conceptual structure designed to sidestep the usual restrictions that short-term memory places on mental processing.
(Ericsson and Pool, 2016, p. 61)
Ericsson, A., & Pool, R. (2016). Peak: Secrets from the New Science of Expertise (1 edition). Eamon Dolan/Houghton Mifflin Harcourt. Peak - Ericsson and Pool