The Double Slit Experiment – Correlation between Mind and Matter?

1. The failure of a materialistic approach to explain consciousness (i.e., attempts to explain mental phenomena arising from a brain that is composed of inert matter) is becoming ever more apparent; see Refs. 1 and 2 below.

2. A number of scientists/philosophers are hoping that quantum mechanics can come to the rescue (Ref. 3,4). They say that even though deterministic Newtonian mechanics is unable to explain consciousness, quantum mechanics can, because quantum mechanics does not have such an apparent deterministic nature.

3. Quantum mechanics (QM) is different from other branches of physics where one can get the intuitive idea of what is taking place. What we do with QM can be called a “black box” approach: when we apply the correct equations, we get the right results. Einstein did not like this at all. Yet, to his frustration, all his predictions of the inadequacy of QM did not materialize AND the predictions of QM have been correct to an amazing accuracy.

4. Those experiments, the results of which can only be explained by QM, APPEAR to be non-deterministic in nature; this has compelled some scientists to investigate whether there is a connection between QM and the mind, which IS non-deterministic. Two experiments in particular have been at the forefront of these discussions: the “double-slit experiment” and the “Schrödinger’s cat experiment”.

5. My intent in this essay is to challenge the two prominent assumptions on this postulated relationship between QM and the mind:

  1. Even if QM and the mind are non-deterministic in their own rights, there is no special reason to believe that there is an apparent connection between them, and
  2. There is nothing really “non-deterministic” about QM, other than the indeterminacy depicted by the Heisenberg uncertainty principle; that is just on the accuracy of a given measurement.

6. Let us look into (i) first. Henry Stapp is a leading physicist who argues that quantum theory will ultimately provide an explanation for consciousness. In his book, “Mindful Universe” he says (p.2), “… quantum theory itself is intrinsically psychophysical as designed by its founders, and as used in actual scientific practice, it is ultimately a theory about the structure of our experience that is erected upon a radical mathematical generalization of the laws of classical physics”.

  • My basic point is that quantum theory is NOT psychophysical; there is no way to accommodate “subjectivity” in QM. Where is the “mind connection” in the theory of QM?
  • There are others who work on theories that try to explain consciousness as arising from quantum effects in the brain; see, for example, “Conversations on Consciousness”, by Susan Blackmore (2006). No one has clarified how these theories make the connection between “psyche” and “physical” in “psychophysical”.

7. Let us review one experiment that has become the main demonstration for the “observer effect” in QM, the “double-slit experiment”. Here is a short video by Dr Quantum to illustrate the “paradox” of the double slit experiment:

8. The two main points of this experiment are:

  1. the particles behave like waves when both slits are open, and
  2. this “wave nature” goes away when the path of the particle is “observed” or monitored.

9. There is a version of QM called the Bohmian theory or the Pilot Wave theory that was developed by the late David Bohm. It does use the Schrodinger’s equation which is used to track the propagation of a “pilot wave”, and the theory is explicitly nonlocal, i.e., quantum entanglement is built-in. With this theory, each solution of the wave equation describes a DETERMINISTIC path for the particle, and statistical average agrees with the experiments and the results of the standard QM calculations.

  • The actual trajectories have been harder to measure not because of a “mind effect”, but because an observation can disturb the particle trajectory itself. Recent experiments have been conducted to “weakly” measure a system without appreciably disturbing the trajectories, and have been shown to be consistent with the predictions of Bohmian theory (Ref. 5).

Thus the role played by Bohmian mechanics in these “QM experiments” is just like role statistical mechanics played in thermodynamics.

Here is a very short video of the INDIVIDUAL trajectories for a double-slit experiment calculated using the Bohmian theory. There is nothing “mysterious”: each particle has a definite trajectory; quantum aspects comes via the “guiding wave”:

  • When it is attempted to observe the path of an individual particle, the coherence of the system or the pilot wave is disturbed and the interference pattern goes away. Thus there is no “observer effect”, in the sense of bringing “subjectivity” in.

10. Another famous experiment that has been the subject of much discussion is the “Schrödinger’s cat” thought experiment. This experiment suggested by Schrödinger back in 1935, involves a cat in a closed chamber. A radioactive sample in the chamber, if undergoes decay within a given period of time, triggers the release of a hammer that breaks a vial of a toxic gas that kills the cat. If conscious observation is required to collapse the wave function, then the fate of the cat is not known until the box is opened. Unfortunately, both the consciousness-based and consciousness-free interpretations of quantum measurement are indistinguishable to the observer outside the box.

  • In 2006,  an actual experiment was conducted to simulate this experiment. It was reported that, “…measurement alone, rather than conscious observation of a measurement, is sufficient”; see Ref. 6.

11. Thus there is no real “observer effect” in the double slit experiments or in the Schrödinger cat experiment.

  • In the double-slit experiment, what an “observer” does is to disturb the coherence of the system, if the disturbance is strong. It does not matter whether the “observer” is human or a mechanical device (in most cases it is non-human); one ALWAYS gets the same result. This is in contrast to real subjective situations, like in the stock market, where complex subjective decisions are made by thousands of people.
  • So, where does the “objectivity” or “intention” – in the sense of the mind affecting the experimental result – comes from? “Intent to monitor” is not really a significant subjective decision; just a simple “yes” or “no”.

12. Therefore, it is clear that there was no evidence for “subjectivity” in those experiments even before Bohmian mechanics or the Schrödinger’s cat experiment; those two pieces of evidence really make that point undeniable. There is no evidence of the mind affecting the outcomes of those experiments.

13. Even though mind affects matter and even CREATE matter, science has not advanced enough yet to confirm that. There has to be a paradigm change: any theory based on matter and attempt to treat mental phenomena as a byproduct will not succeed. Mind is the more fundamental entity; mind takes precedence over matter.

  • Some philosophers are beginning to sense this reality. Even though he does not appear to know anything about Buddha Dhamma, philosopher Thomas Nagel says: “The great advances in the physical and biological sciences were made possible by excluding the mind from the physical world…..But at some point it will be necessary to make a new start on a more comprehensive understanding that includes the mind”. (Ref 1, p.8). Then on p. 15, “…The possibility opens up of a persuasive conception of the natural order very different from materialism – one that makes mind central, rather than a side effect of physical law”.


  1. Thomas Nagel, “Mind and Cosmos” (2012).
  2. Colin McGinn, “All machine and no ghost- McGinn-2012”, New Statesman p. 40, February 20, 2012. (click on the link to open the pdf file)
  3. Henry P. Stapp, “Mindful Universe” (2011).
  4. B. Rosenblum and F. Kuttner, “Quantum Enigma – Physics Encounters Consciousness”, (2006); there are many other recent books.
  5. S. Kocsis et al., “Observing the Average Trajectories of Single Photons in a Two-Slit Interferometer“, Science,  vol. 332, 1170 (2011). (click on the link to open)
  6. R. H. S. Carpenter and A. J. Anderson, “The Death of Schrodinger’s Cat and of Consciousness-based Quantum Wavefunction Collapse“, Annales de la Fondation Louis de Broglie, vol. 31, 45 (2006). (click on the link to open)
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