Occam’s razor and rules of thumb

Occam’s razor (make fewest assumptions, eliminate the unnecessary, the simplest is best, postulate the fewest entities) is a rule of thumb for science. Another rule of thumb is that general theories that cover large amounts of data are preferable to a number of smaller theories covering the same data.


So what can we make of a recent article (here) in the New Scientist where Henry Nicholls reviews attitudes towards the idea of animals having the ability to ‘time travel’ through their memories and imagined futures and are not confined to just living in the present.

“The issue is getting researchers of human and animal minds rather hot under the collar. Critics argue that what looks like memory or forward thinking is nothing more than instinct or learned behaviour, and insist that there is no convincing evidence that non-human animals can remember their past or contemplate the future. As a result, every paper claiming to demonstrate the ability in animals is fiercely debated.”


The article reports on a number of experiments that appear to show memory or foresight and then reports the criticisms. The same disagreements occur fairly often in the areas of animal communication, use of symbols and concepts, calculations, self awareness etc. Sometimes the critics seems to me to be right but more often they appear to be putting forward ideas that do not pass the Occam’s razor test and postulate one theoretical framework for animals and another for humans, with no reason to justify the difference.


Some would say that there is another principle to keep in mind – don’t anthropomorphize. When I look at a chimp and I say he is standing on his legs and waving a branch with his arms, I am not criticized for using the same word for the chimp’s legs and mine or the chimp’s arms and mine. We are allowed to say that an animal is angry or frightened. We recognize homologous features in different animals and ourselves. But if we talk about animals having concepts, we are said to have crossed a line and are anthropomorphizing. This is a circular argument: first we have to define something as a human-only attribute and then we are anthropomorphizing if we use a human-only attribute in the context of an animal. If the attribute had not been defined as uniquely human in the first place then there would be no anthropomorphizing.


There are a number of reasons to avoid failing into the trap of exaggerating the differences between us and animals (especially the intelligent and social ones) and therefore defining ahead of investigation that some explanations only apply to humans.

1.      There are experiments that can be done with animals but not humans and vice versa. We can understand both better if we consider what we know about the other.

2.      The same reasons that behaviourism is no longer convincing for humans can be applied to animals.

3.      The brains of many animals are similar to human brains. There is the same chemistry and physics and biology, the same evolutionary history until very recently, and very similar basic behaviour. There is no enough difference evident to justify two types of explanation. It is not good science to burn bridges or lock doors ahead of experimental evidence.

4.      A difference in degree can be large enough to look like a difference of kind.

5.      No explanation of human neurobiology is complete without an evolutionary narrative of how it evolved from common ancestors with other primates. This would need to show the steps that connect human thought to animal thought – difficult if there are different mechanisms put forward for what appears to be the same abilities.

6.      Humans are unique but so are all species (it is sort of the definition of a species). Humans may even be ‘uniquely unique’ but I doubt that they are the only species that could be called that. But uniqueness is not an important criterion for understanding how brains/minds work – whether an explanation fits depends on the explanation and not on its uniqueness.

7.      Science should be protected with other agendas. Part of the motivation for separate explanations for humans and animals is prompted by agriculture, religion, and various philosophical or pragmatic ‘vested interests’.


2 thoughts on “Occam’s razor and rules of thumb

  1. Good points. It really seems a bit silly to try to make a very distinct separation between humans and other animals in terms of cognitive capabilities, when the unity among different kinds of organisms is an such a clear implication of evolution. I’m not sure what kind of an evolutionary mechanism would produce such a very clear-cut distinction between the entire animal kingdom, and one particluar species within it.

    • “I’m not sure what kind of an evolutionary mechanism would produce such a very clear-cut distinction between the entire animal kingdom, and one particluar species within it.”
      Although I agree with most of this statement, while reading it a possibility came to mind. I think the only apparent clear clear-cut distinction between humans and the animals could be our awareness of our process of thinking. From Descartes we get “Cogito ergo sum” . He started proposing that he would doubt everything, therefore he exists as something that doubts everything. So he must exists. Can a monkey do that? Maybe they can, and they just do not want us to know that they can.

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