A method on a computing device is provided for enhancing the memory and cognitive ability of an older adult by requiring the adult to differentiate between rapidly presented stimuli. The method trains the time order judgment of the adult by presenting upward and downward frequency sweeps, in random order, separated by an inter-stimulus interval. The upward and downward frequency sweeps are at frequencies common in formants which form the frequency components common in speech. Icons are associated with the upward and downward frequency sweeps to allow the adult to indicate an order in which the frequency sweeps are presented (i.e., UP-UP, UP-DOWN, DOWN-UP, and DOWN-DOWN). Correct selection of an order causes the inter-stimulus interval to be reduced, and/or the duration of the frequency sweeps to be adaptively shortened.