I learnt from reading Michael Freemans' book The Photographers Eye that the 'Contrasts' task is nothing new, as it actually dates back to Bauhaus circa 1920. There it was a task set by Johannes Itten, the Swiss expressionist painter, as part of the 'Basic Course'.
Freeman, M. 2007. The Photographers Eye. Lewes: Ilex.
Wikipedia. 2014. Bauhaus. [online] Available at: http://en.wikipedia.org/wiki/Bauhaus [Accessed: 18 Feb 2014].
Wikipedia. 2014. Johannes Itten. [online] Available at: http://en.wikipedia.org/wiki/Johannes_Itten [Accessed: 19 Feb 2014].