Some Factors Affecting Necker Cube Reversal Rate

Since eye movements have been ruled out as a major soiuce of reversible figure fluctuations (Pheiffer, Eure, 8: Ham~lcon, 1956; Pritchard, 1958), explanations of the cause of the initial reversal, as well as of the frequently reported increase in reversal rate over increasing observation time, have centered mainly around two competing theories: the satiation theory of Koehler and Wallach ( 1944), and the learning theory of Ammons and his co-workers (Amster, 1951; Ammons, 1954; Ammons, Ulrich, & Ammons, 1959). Satiation theory stresses the physiological nature of the phenomenon. According to this theory, progressive cortical satiation, thac is, a progressive selflimiting and blocking of cortical current activity, occurs in the cortical area isomorphically representing the forward aspect of the cube. At some critical threshold point the current is sufficiently blocked and deflected into neighboring areas so that the second aspecc of the cube will achieve figural dominance. W h e n this second aspect of the cube in turn reaches a critical satiation level, deflection of the current will once again shift the figure-ground relationship and the first aspect of the cube will regain its figural qualities. However, since the satiated tissue will not have recovered completely, its critical threshold point will now be lower. For this reason, reversals will gradually increase until some maximum reversal rate is reached a t which poinr, since the entire area would be highly satiated, it is possible that there might be some slight decline in the reversal rate. Familiarity with the way the cube reverses seems to cause some increase in the inicial rate of reversals, but it is quite clear thac satiation theory relegates to familiarity or learning, in the usual interpretation of these rerms, a relatively minor role. McDougall's ( 1906) earlier physiological explanation is very similar in many aspects to the satiation hypothesis. Learning theory, on the other hand, stresses the roles of experience and subjective set. The increased reversal rate over time is ascribed t o practice, and the fact that Ss can influence the reversal rate by certain learned strategies is cited as evidence of the major influence of learning in producing the fluctuations.