<prompt> The learning theory of digit sucking was proposed byDavidson, 1967Sears and Wise, 1982Johnson and Larson, 1993Sigmond Freud, 1905  <response>: The learning theory: Davidson 1967This theory advocates that non-nutritive sucking stems from an adaptive response.The infant associates sucking with such pleasurable feelings as hunger. These events are recalled by sucking the suitable objects available, mainly thumb or finger. 