“…The criterion tasks were the Marble-in-the-Hole persistence game employed by Berkowitz and Zigler and a two-color discrimination learning task. The latter measure was used in order to circumvent some of the difficulties, for example, position preferences, which recently have been found (Parton & Ross, 1965;Patterson & Hinsey, 1964) with the typical preference-switching marble game as a learning measure. Since the four preliminary tasks and the Marble-in-the-Hole Game are described in some detail elsewhere (Berkowitz & Zigler, 1965) a description of only the learning apparatus will be included here.…”