This usage derives from Miller's (1956) idea of chunking as grouping, but the emphasis is now on long-term memory rather than only on short-term memory. A chunk can then be defined as "a collection of elements having strong associations with one another, but weak associations with elements within other chunks".[20] Chase and Simon (1973) and later Gobet, Retschitzki and de Voogt (2004) showed that chunking could explain several phenomena linked to expertise in chess.[20][21] Following a brief exposure to pieces on a chess board, skilled chess players were able to encode and recall much larger chunks than novice chess players.