to the optimal complexity level of the organism. It should be noted. however, that the relationship may not be as strictly symmetrical as suggested in the schematic example in the figure. The addition of Dember and Earl(1957) to the theory is the introduction of the idea that the organism's optimal arousal level-or optimal level of perceived complexity as they call it is not stable, but can be increased by exposure to stimuli that are a little more complex than the optimally preferred one, whereas exposure to stimuli with lower than optimal complexity would just be perceived as boring, but would leave the optimum level of perceived complexity of the organism Thus, exposure to such a slightly more complex than unaltered. optimal stimulus B in Fig. 11.1) -called a pacer by Dember and Earl would cause a shift in the appreciation of all stimuli(see dotted line in Fig. 11.1) causing the originally most liked stimulus to decrease in pleasantness for the organism.