Do Cats Collapse the Wave Function? Confronting the Measurement Problem with Subliminal Priming
Perhaps no metaphysical question is more fundamental than the question: what is the primary constituent of reality? Is physicalism correct and only physical things exist, or are the non-physicalist approaches (Dualism, Idealism, Neutral Monism) which consider consciousness to be in some way fundamental, correct? The Consciousness Causes Collapse (CCC) interpretation of Quantum Mechanics ties consciousness inextricably to the most fundamental workings of physical reality. It is therefore incompatible with physicalism. But is this interpretation true? Can it ever be tested, falsified? The problem with testing the CCC is experimentally determining whether the interaction with the physical measurement device caused collapse or if conscious observation caused it. These two appear to be hopelessly intertwined. How do you measure something without observing it? In this way the superposition is like the darkness in the refrigerator. Every time you open the door and look inside the light is on. You don’t get to see the darkness, even though you know that it is there.
Research methods in cognitive psychology can provide a way forward. The well-established experimental methodology of subliminal priming allows us to measure the light in the refrigerator without opening the door. In cognitive psychology, the term priming refers to an effect where exposure to one stimulus influences a person's response to another stimulus. For example, a positive word such as “happy” is recognized and responded to faster after the word “joy” as compared to a negative word such as “sadness” or “death”. The word “up” is responded to faster following a prime such as “high” or “top” as opposed to “bottom” or “low”. Psychologists have been exploiting these reliable reaction time effects for decades as a multipurpose research tool. In recent years, these methods have even been used to prime subjects subliminally. In such research, subjects are flashed a prime (such as a word or a symbol) on a computer screen for a length of time that is just underneath the duration that can be consciously experienced (50 milliseconds). Despite subjects reporting to not be aware of seeing the prime, they demonstrated shorter reaction times responding to stimulus that is congruent with the prime than to incongruent stimulus. Their brains processed the meaning of the prime and began to react to it even though they were not aware of it. This ability for humans to process information unconsciously makes it possible to measure the effects of something that is itself shielded from conscious observation. By deriving the direction of the primes from quantum events we can leverage subliminal priming to put the CCC to an experimental test.
Two experiments were conducted to test whether it is the interaction of quantum phenomena with a physical measurement device or conscious observation that causes its wave function to collapse. In both experiments stimulus primes derived directly from quantum phenomena were flashed on a screen for a duration of time too brief to be consciously experienced. They were immediately followed by a stimulus that participants were asked to rapidly respond to. The stimulus was designed to be congruent with some primes and incongruent with others. If conscious observation caused collapse, the primes, having been shielded from consciousness, should continue to exist in a state of superposition based on the quantum phenomena from which they were derived. Before the participants took the reaction time test, a third of the primes were observed by the experimenter, a third remained completely unobserved, and a third were observed by a cat. If consciousness caused collapse, shorter response time differences would be expected in the primes that remained unobserved as opposed to those previously exposed to observation. This is because a prime that is still in a state of superposition should be simultaneously congruent and incongruent with the stimulus. However, if conscious observation had nothing to do with collapse, then the collapse would have occurred upon the quantum phenomena's initial interaction with the physical measurement device, and there ought to be no significant difference between the performance of the observed and the unobserved primes.
The results obtained provide direct evidence in support of the CCC interpretation of quantum mechanics. The primes in both experiments that were subjected to prior human observation had a greater effect on reaction time than those that were denied that observation. Primes previously observed by the cat did not have any greater effect than those that remained completely unobserved, a finding which suggests that wave function collapse may be tied to a feature of human consciousness which is not universally shared
