The Clumping Effect

by Rich Feldenberg

Cognitive biases permeate our thinking process, leading us to false conclusion and beliefs. Aristotle called humans, “The Rational Animal”, but it has been pointed out before that we are much more rationalizing than rational. We have a strong tendency to hold onto our notions, defending them with faulty logic and weak arguments, because we wish them to be true. Motivational reasoning and emotional argument is common to see in even very intelligent and educated individuals. Daniel Kahneman helped to define the idea of cognitive bias, and popularized it in his book, “Thinking Fast and Slow”. Over the decades the ways in which evolution has mesigned the human mind to fail the litmus test of reality testing has been more fully explored, and the list of cognitive biases, logical fallacies, and faulty brain circuits continues to grow ever longer.
I would like to introduce what I believe is a new, and as yet, unidentified type of cognitive bias the I’m labeling as “The Clumping Effect”. I have noticed this effect in myself over the last few years, and although I have not done a statistical analysis of the effect, feel it can be nothing more than a cognitive bias. The effect occurs when I am on the trail, either on my bike or running. The nature of the effect is this: If there is a stretch of trail with few runners, walkers, and cyclists, I notice that if there are two other people on the trail that are separated from each other at time 1 (when I notice them), then the three of us all converge at the same spot (time 2). In other words, if I’m on my bike I don’t just pass the first person and then later the second person, we all happen to be along the same point of the path together at time 2.
This effect can occur if all three subjects are moving in the same direction, or if two or moving in the same direction and one in the opposite direction, but all subjects must be moving at different velocities. In this definition I’m using the term velocity in its true physical sense (speed and direction), because you could for instance, have two bikes moving at the same speed, but opposite direction. Place a runner in-between the bikes and the Clumping Effect demands that the three will pass each other at the same point.
I notice this because it is somewhat annoying to be a cyclist, moving at a good clip on an empty trail, then have to be cautious about avoiding a collision when the lone spot of the trail is suddenly at full capacity. And, that I believe is the underlying reason for the Clumping Effect. It is those instances that stand out in my mind, whereas the many times that I pass one athlete then the other doesn’t really register as an event at all. We remember the hits and forget the misses, as any good skeptic knows.
I would be interested to know if anyone else has ever experienced a similar effect. I may also decide to do an experiment to measure the incidence of “hits” in comparison to “misses” on my typical trail. I’m curious to know do ‘hits to misses’ happen at a rate of 1:100 for example. How often does it have to happen that it stands out in my mind as something that “always happens”. Also, what proportion of users of the trail also notice the effect? I could send out a survey to local running and cycling groups?

References and other sources of good info:
1. Cognitive Biases Wikipedia article:
2. Daniel Kahneman Wikipedia article:
3. “Thinking Fast and Slow” by Daniel Kahneman. I really recommend this book.
4. “The Skeptics Guide to the Universe (SGU)” podcast. Great free source of information on how to think logically.
5. “Neurological” Blog by Dr. Steven Novella. Also filled with great information on skeptical and logical thinking.
6. “The Rationally Speaking Podcast”, host Julia Galef.
7. SGUs guide to argument and logical fallacies:

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