The “Observer Effect”
One of the unsolved puzzles in quantum mechanics is known as the “measurement problem.” The classic way to demonstrate this problem is with a double-slit optical system. In such systems a beam of photons, such as that produced by a laser, is directed to pass through two tiny slits. A camera on the other side of the slits captures how the photons behave after they go through the slits. If nothing is known about which of the two slits each photon goes through, then the pattern observed by the camera is alternating light and dark bands. This is what one would expect if photons behave like waves. Waves, like ripples in a pond, can interfere with each other and in so doing they produce a characteristic pattern of peaks and troughs (or in the case of photons, lighter and darker bands of illumination).
However, if it is known which of the two slits the photons pass through, then the wave-like behavior disappears and the camera sees a pattern consistent with photons behaving like particles. This dual nature of light, wave or particle, depending on what you know about it, is a puzzle because why does a photon care if it is being observed?
Many interpretations of this “observer effect” have been offered. A long line of prominent physicists have suggested that this phenomenon may offer a clue about the nature of consciousness, because it is only through our conscious awareness that we know the world. Thus, if photons behave differently depending on what is known about them, then could it be that consciousness somehow “collapses” the quantum wave-like description of the physical world into classical particle-like behavior?
To put this idea to the test, over two decades a series of 30 experiments were conducted in the IONS lab and four other labs in the US, Canada, Brazil, and Serbia. These experiments asked participants to focus their attention toward or away from a double-slit optical system. When focused toward the system, the participants were to hold the intention to gain information about the behavior of the photons after they passed through the double-slit (usually accomplished by watching a real-time feedback signal, such as a line graph being drawn on a browser, that indicated whether the interference pattern was either more wave-like or particle-like). The hypothesis proposed that when attention was focused toward the optical apparatus, the photons would transition from wave-like behavior to particle-like behavior. The degree to which this transition would occur was expected to be proportional to how well the participants could focus their full attention on the task.
Out of the 30 reported experiments, 14 reported statistically significant results (at p < 0.05, two-tailed). By chance, one would only expect 1 or 2 studies to show significant results, so this outcome suggests that there may be something peculiar about consciousness after all. Many of these studies were exploratory, so to confirm these results we will need many more formal, pre-planned experiments.
Mind-Wandering Human Nature
In the meantime, while we are waiting for those studies to be conducted, we already know that the results in these studies are highly variable both across different participants, and even within individuals. One reason for this variability is that, as we had expected, the predicted outcome depends on the participant’s ability to tightly focus their attention, and most people find it difficult to maintain that kind of focus for more than a few seconds. Every beginning meditator knows that their attention is constantly fluctuating. This unavoidable “mind-wandering” reduces the effectiveness of this kind of attention-demanding experiment.
Perhaps, then, an alternative is to accept that focused attention is unstable. Under that assumption, we can postulate that when people are attempting to focus their attention toward the apparatus, that the camera will observe more fluctuations (wave-like to particle-like behavior, and vice versa) in the interference pattern than when the camera is recording but no one is looking at the results.
Re-examining the Data in a Novel way
This requires a different kind of analysis of the experimental data. Technically speaking, instead of looking for a shift of the mean in the data (what we would expect with perfectly focused attention), we look for a shift in the variance of the data, or the variability, since we expect focused attention to come and go as a result of mind-wandering. This is what we found and reported in our new study.
We found strong evidence in a previously conducted double-slit experiment from our IONS lab that a variance-shift measure was indeed a more sensitive way to detect the effect of consciousness in a double-slit system than a mean-shift measure. In other words, rather than seeing human observation cause a clear transition from wave-like to particle-like behavior, we saw more variability between these two states (when compared to a control condition), presumably as a result of fluctuating human attention.
This finding is useful because it may provide a more sensitive way to measure what happens in any form of mind-matter interaction experiment by more accurately taking into account the real-life behavior of human minds.