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The Biology of Scepticism

Humans and animals could not survive without beliefs. Beliefs are pieces of information that we assume to be true and as such they regulate our decision making in every social and ecological context. In humans and other animals, beliefs are created by the continuous sampling of the environment through our perception and as our experience of an event increases with frequency, the belief of its future occurrence becomes crystalized. But in humans, there are other sources of beliefs which seat on the transmission of ideas through communication. Such transmission is affected by external and internal factors. The external factors are cultural and based on meme repetition, ritualization and social position in the group. The internal factors are inherent to the individual and its psychology as its degree of credulity and acceptance of authority, its willingness to conform to the group dynamics and the meaning that each one of these memes has to the individual.

The strength to which each one of these memes is adopted and protected depends also on the qualities of the meme itself.  I have identified 6 factors that contribute to the stickiness of a meme:

  1. Emotional

Does the meme trigger strong emotional reactions?

Does it trigger positive emotions such as reward or pleasure, or negative emotions such as punishment, fear, guilt?

Is it memorable?  Is it salient?

That’s it value oneself as an individual?

Does it reduce anxiety due to unpredictability?

  1. Intuitive

An intuitive is one which agrees with our intuitions. For example does it agree with folk physics, biology, and psychology?

Does it agree with our cultural imprinting during a sensitive developmental phase?

  1. Causal

The meme explains the causes of events.

  1. Predictability

Does the meme offer some level of predictability to the random events of nature and social interactions, does reducing individual anxiety and stress levels?

  1. Reliability

Is the meme consistent in its narrative? Does it make sense in answering the main questions of life?

  1. Functionality

Does the meme offer pragmatic solutions to the questions of life?

 This list was created in function of the main questions that affect us all at different stages of our psychological development. Such questions can be divided into two categories: questions of empirical nature and existential questions.

Questions of empirical nature as things like; What or who causes the phenomenon?  How does it work? How often does it happen? What is it for? And they beg for answers that refer to causation and agency, mechanisms, patterns and utility.

Some of these questions are believed to occur in the minds of other animals, Not in the shape of verbal sentences but more in practical terms such as when a Capuchin monkey assesses the suitability of a stone to break a nut, or a New Caledonian Crow observes and learns the technique of using sticks to fish for grubs in decaying trees.

Animals have also some sort of pattern detection which allows them a certain level of predictability tweaking their behaviours in accordance with expected changes.

So it is reasonable to assume that some of these empirical questions may have roots in some evolutionary antecedents.

Existentialist questions, however, are more abstract and they focus on the issue of meaning, purpose and life as a finite entity. Questions about immortality and purpose are related to the philosophical approaches to telos.


















(Click on images to see them enlarged)



Beliefs that satisfy many of these conditions and answer these questions are likely to be persistent in the mind for they serve a purpose. Questioning such beliefs requires a considerable amount of scepticism, which does not come naturally in human minds. Or does it?

The history of philosophy has shown us that scepticism has been around for many centuries and therefore it is not a function of cultural evolution. In fact if belief may bring some evolutionary advantages in reducing stress, scepticism may also contribute to a balanced evaluation of information and a proper screening of the reliability of the information.

The assessment of signals is a behavioural characteristic present in many species. It is important that animals can detect dishonest signals. Those better at their detection and more likely to survive. Thus scepticism can also be seen as a natural mechanism biologically grounded to detect dishonest or misleading information. Both systems belief vs scepticism compete for place in the individual mind and natural selection might have selected one in detriment of the other in different situations. There are situations where belief conformity is advantageous for a social group, but scepticism may also prevent the group from setting themselves into danger.

A good leader would be one who can balance both traits and use them in the right situations.  This begs the question; is the tendency for belief and scepticism a biological tendency, rather than a cultural trait? Culture may emphasise this tendency which is expressed only in the presence of the right triggers.

Assessing individual differences in levels of scepticism versus credulity  is important for our modern society as it allows us to detect who is more susceptible to cheating . In practice the propagation of internet phishing schemes rely very much on the propensity of some people to be uncritical.

To investigate this question, it is necessary to see if there is psychological individual variation in the levels of credulity.

If that is true, the next step is to investigate if this variation is due to cultural or biological mechanisms?

Why would some individuals born and raised in the same cultural setting and studying the same University Course vary in their level of acceptance of memes and levels of critical reasoning?



The rejection of mainstream, widely accepted beliefs is usually perceived as scepticism, but we need to be clear about the meaning of this word for scepticism is used in different situations in loose ways. Usually it is perceived as an attitude of doubt in relation to the truth of received information.

If I receive an email from Nigeria telling me that the widow of the deceased president of a large company wants to share her inheritance with me because we share the same surname, I have good reasons to be sceptical. I’ll ask first where did they get my email? How do they know her connections to my family, and so on?  My scepticism prompts me to ignore that email and protect myself from some internet scam. However many people are susceptible to such scams. It is yet more difficult to assess the truth of the information when these tricks become even more complex and sound plausible. In such situations scepticism as a gut feeling is not enough. To protect myself I need to be able to ask questions which will enable me to assess the veracity of such information. Such questions depend not only on my tendency to be careful about received information, but also on some sort of mental training in assessing the reliability of information. Such training can be achieved through education and the practice of critical skills which helps us to analyse our own bias.

There are variations in the natural tendency to assess the reliability of information. Some humans may be more prone to readily accept it without scrutiny, whether others may be more careful in relation to embracing such information. This variation in human individuals begs the question; is it due to cultural or biological influences?

To answer this question, one needs to search for signs of scepticism in species other than humans, and understand which neurobiological mechanisms are involved in the tendency to question information. The biological explanation of scepticism requires an ultimate and a proximate explanation, based respectively in the evolutionary advantage of carefully evaluating information and which brain mechanisms are involved in such questioning which could be susceptible to variation and eventually genetically determined.

Scepticism and belief are two sides of the same coin. Whereas in humans, belief consists in accepting a piece of information as being true, scepticism questions that truth, which brings us to the need to understand the concept of truth and its importance in survival.


In philosophy, scepticism is a position which questions theories that discuss truth, knowledge and belief. These three concepts are closely related, in philosophy to have knowledge means that we have reasons to believe that the information that we uphold is true and the process to assess truth is through the acquisition of evidence.

Whenever a person holds a belief, that person assumes it is true, even if it is not in real life. If I believe in fairies, I hold it as being true. But is that knowledge? Not until I gather enough evidence for the existence of fairies.

The branch of philosophy concerned with theories of knowledge is called epistemology and it defines knowledge as justified belief. This requires the clarification of the concept “justification”.

The philosophical approach to scepticism is not relevant to the evolutionary discussion, but the history of philosophical scepticism offers an overview of how ancient is this attitude in the evolution of the human mind. The most ancient written records provide us with examples of sceptical questioning of the beliefs held at the time.

Before scepticism became a complex issue of epistemology, it originated as a questioning of authority which rested on unsupported assumptions. Seen this way, it is reasonable to assume that scepticism may have its roots well beyond the invention of writing. It might have been upheld by individuals inside a group which questioned the authority of tribal chiefdoms. Some individuals might have refused to abide by rules created by the caprices of tribal leaders. They would question such orders, costumes or taboos and require justifications for why should they follow it. This attitude might have been in the origin of abstract thought and complex metaphors.

A primitive sceptical dialogue would have been similar to this:

“You must do this because the chief says so”;

“And why should I believe the chief? On which authority is he requiring of me to do so?”

“ Because the chief is the voice of the spirits of the elders”

“ And how can he prove that it is true and he is not  lying to me just to make me offer my life for his own interests?”

The non-conformism shown by sceptical could simply be removed from the group through extermination or ostracizing, but the questioning would certainly be embraced by others who might have felt that unfairness was imposed upon them and thus the need to create justifications for the power of the chief becomes necessary. Oral justification might yet been more necessary when a critical mass of sceptics begins to rise among the group members. Then simply exterminating them would lead to a loss in valid members of the tribe, necessary to its defence against competing or threatening out-groups.

Philosophical scepticism entered the western culture through Pyrrhonism, a  school of philosophy with its roots in Classical Greece ( c. 360-275 BC), but scepticism had been expressed much earlier  well before the Greeks in Indian philosophy through the Carvaka materialists ( 6 century BC) who denied the concept of karma and rebirth. The Carvaka School is a current of Hinduism that rejects the supernatural through an emphasis on materialism and philosophical scepticism an d holding empiricism and perception as a necessary condition for the acquisition of knowledge.

So scepticism is not a new concept and developed during the Enlightenment, although it was during this period that Pyrrhonic scepticism was rediscovered and promoted.

A certain level of scepticism is thus necessary to the evaluation of the reliability of messages that may threaten the very existence of an individual. Under this approach, scepticism can then be treated as a mechanism to assess the reliability of information crucial for survival. The concept “information reliability” is the ecological equivalent of the philosophical concept of truth.

It is important not to confuse philosophical scepticism with irrational scepticism, which simply consists of doubting everything that is ascertained. This type of scepticism is exemplified in the rejection of evolution theory by creationists, or global warming by climate change sceptics, or the rejection of membership of the European Union by the so called Eurosceptics.

Note that in such circumstances, the word scepticism does not refer to the pursuing of knowledge through evidence, but rather a stubborn attitude to contradict mainstream beliefs.



There is a body of studies showing that cheating occurs in nature in many animal species, but it is important to distinguish between evolutionary cheating and intentional cheating.

The first refers to signalling systems which have evolved to mislead possible predators or competitors. The second refers to the presence of intentionality which requires a certain level of consciousness. For example, mimicry in nature is a form of cheating leading predators to confuse palatable prey with poisonous prey, but in this example when a scarlet king snake  mimics the poisonous coral snake, the mechanisms is not intentional. Scarlet king snakes became similar to coral snakes simply due to the processes of natural selection. However there are instance in animal behaviour which lead us to assume that there is certain level of intentional signalling. Some birds may simulate behaviours which lead a predator to assume the bird is injured, just to distract the predator from the position of the nest. It is not clear if this behaviour is intentional or just an automatic behavioural response that was positively selected through evolution as it brought some advantage to the survival of the offspring. However, even though the behaviour is fixed or instinctive, the decision to when to express it may bare some level of intentionality.  There are examples from studies of primate behaviour that some dishonest signals are indeed intentional. When dishonest signals are so widespread in nature, a mechanism of detection might have co-evolved with the signal. Cheating and detection can then be seen as a type of evolutionary arms race.

The mechanisms of cheating detection depend on which cues are used by each species as means of communication.  If communication is essentially based on sound, the receiver needs to develop mechanisms that detect faked signals in the sound waves. If communication is mainly visual, then the receiver of the message needs to detect small variations in the received images to detect what to trust. In humans and other primates were communication owns much to facial expressions, detection of lying is often based on subconscious perception of facial cues. This is why some people can say that they have a “feeling” that someone is lying, but they can’t really explain how they know it. Just as with pheromone detection, the perception of these visual cues does not necessarily reach our consciousness. Some people may be more accurate in this detection than others, but this is a system which has evolved by natural selection without interference of intentionality.

This natural tendency to detect cheats may be closely related to a propensity to the exercise of scepticism. My theory is that this propensity is an evolutionary by product built on the same neuronal pathways which enable detection of cheating.  The difference is that scepticism builds on the rise of consciousness and a tool that finds expression in the frontal cortex.

Note that the propensity for a particular trait does not mean that such trait is necessarily expressed. A propensity simply indicates that given the right environmental or social trigger the trait could be expressed, but if the trigger is never present it may never surface. For example some dogs may have a propensity to be more aggressive than others, but if they exist in environments that never require the expression of aggression, that trait may not be expressed. A propensity for a trait means that the trait is only expressed out of necessity.


(To be continued)