 These anomalies for behaviorism fill rationalists with mixed emotions. On the one hand, the experiments refute the empiricist principle that everything known about the world is learned from experience. On the other hand, the experiments also constitute a caution against over-intellectualizing absences. A correct explanation of emotional engagement with absences must be more general and cognitively less demanding than rationalists tend to presuppose. Even mosquito larvae see shadows. Doubts about whether they have consciousness do not make us doubt that they see shadows. So the perception of absences cannot depend on consciousness or any other advanced mental state. Perhaps the earliest form of vision was of these absences of light. So instead of being a pinnacle of intellectual sophistication, cognition of absences may be primal.