“Do philosophers really think differently than non-philosophers?”

That’s the question taken up by a team of researchers in a recent study published in Philosophical Psychology. Focusing on differences between philosophers and non-philosophers in regard to neurodivergent traits and responses to thought experiments, the researchers found some support, in the aggregate, for a “yes” answer to that question.

The following guest post is by Thomas Nadelhoffer (College of Charleston), and is based on the article, “Thinking Differently: Neurodivergent Traits and Responses to Thought Experiments in Philosophers and the General Population,” co-authored with Paul McKee (Duke), Khaoula Boulhadi (Southern Connecticut State), and Helena Weymouth (College of Charleston).

How Different Are Philosophers?

by Thomas Nadelhoffer

“The history of philosophy is to a great extent that of a certain clash of human temperaments [. . .] Yet, his temperament really gives him a stronger bias than any of his more strictly objective premises. It loads the evidence for him one way or the other” — William James

Neurodiversity and Philosophical Intuitions

In addition to being abstract thinkers, philosophers are stereotyped as being argumentative, overly self-absorbed in their own thoughts, and enjoy creating increasingly fine distinctions regarding everyday terms while imagining novel hypothetical situations and debating the conclusions they draw. It’s possible that many philosophers have quite distinctive personalities.

More than two millennia before the modern notion of stereotypes existed, Plato used humor to poke fun at philosophers in the Theaetetus by telling a story of Thales contemplating the stars, so engrossed that he forgot where he was walking and fell down a well. However, do philosophers really think differently than non-philosophers?

This was one of the questions behind the paper we recently published in Philosophical Psychology. We surveyed 1,254 individuals, 632 with formal training in philosophy and 622 members of the general public, and explored whether philosophers exhibit significant cognitive differences from non-philosophers using multiple measures of neurodiverse traits. To get enough responses from philosophers, we recruited participants here at Daily Nous and on Leiter Reports. We recruited the general population participants from Prolific. We preregistered our experimental design, research questions, and hypotheses.

Philosophical Temperament?

Recently, experimental philosophers and psychologists began investigating philosophical temperament, that is, the study of relationships between psychological traits and philosophically relevant judgment. Several studies have linked various personality traits to judgments concerning issues like free will, moral responsibility, intentional action, and metaethics. Research has also demonstrated that although trained to reason about certain things rationally, philosophers are susceptible to psychological factors influencing their philosophical intuitions. Our aim was to investigate this area further.

Rather than continuing to focus on personality characteristics that researchers typically measure using personality surveys (e.g., The “Big Five”), we decided to examine characteristics that relate to the following neurodiverse traits:[1] autism; ADHD; aphantasia (low visual imagery); anendophasia (i.e. low levels of “inner speech”); and representational manipulation (the ability to mentally manipulate and modify representations).[2]

Of the four significant differences found amongst participants from the general population and those with some degree of formal training in philosophy:

- Philosophers exhibited higher levels of ADHD-related traits (moderate effect size, d = .5).

- Philosophers exhibited lower levels of visual imagery (substantial effect size, d = -.6).

- Philosophers exhibited higher levels of internal speech (smaller effect size, d = .34).

- Philosophers demonstrated higher levels of representational manipulation (substantial effect size, d = .76).

All four differences found were very stable, even after we limited the criterion for “philosopher” as only participants with PhD degrees or postdoctoral appointments in philosophy.

Therefore, our findings suggest that, as a group, philosophers have a distinct cognitive profile (relative to the general population). This profile consists of higher levels of internal verbalization, enhanced capacities for mentally manipulating internal representations, lower levels of visual imagery and higher levels of ADHD traits.

Philosophers and Thought Experiments

All participants completed two classical versions of this type of experiment: the “bystander at the switch” version of the trolley problem and the “rollback universe” deterministic universe.

We also assessed how often each group misinterpreted determinism, through either bypassing (treating an agent’s beliefs, desires, and deliberation as having no causal relevance to their actions) or indeterminate intrusion (allowing multiple possible outcomes while maintaining identical initial conditions and laws).

As before, there were significant differences between philosophers and non-philosophers.

In the trolley case, philosophers were significantly more likely to believe it is acceptable to sacrifice the one person but not obligatory and less likely to believe that it is unacceptable.

In short, there was a small yet statistically reliable correlation between being a philosopher and intuitions about the bystander at the switch scenario.

However, there were larger differences in the responses to the determinism case. Approximately 50% of philosophers believed that agents in the deterministic universe have free will. In comparison, approximately 37% of members of the general public reported the same intuition. For moral responsibility, approximately 69% of philosophers and 54% of the general population judged that agents in the rollback universe are responsible. Moreover, philosophers made the bypassing error much less frequently than did members of the general public. While 17% of philosophers made this error, 63% of those in the general public made it. Similarly, while approximately 25% of philosophers made the intrusion error, approximately 33% of members of the general public made it.

Our next goal was to assess if there existed a connection between the cognitive characteristics of our subjects and their responses to philosophical thought experiments. We found that psychological traits are correlated with responses to thought experiments independently of the subject’s exposure to philosophy. Visual imagery provides a good illustration. Those who reported lower levels of visualization were more likely to make utilitarian judgments in response to the bystander at the switch scenario. Conversely, those who reported more vivid visual imagery were less likely to indicate that flipping the switch was permissible but not obligatory.

Furthermore, visual imagery influenced judgments regarding determinism. Those who indicated higher levels of visual imagery were less likely to assign free will and moral responsibility to agents in the rollback universe. Additionally, individuals with lower visualization scores were more susceptible to both bypassing and intrusion errors.[3]

Machine Learning and Sorting Philosophers and Non-Philosophers

The final analysis that we ran involved using various machine learning algorithms to see whether we could predict whether we could accurately distinguish between philosopher and non-philosophers using neurodiverse traits, responses to thought experiments, and both taken together. So, we trained various machine learning models to determine if they could categorize participants into either philosophers or non-philosophers.

For the first round of analysis, we provided the models with only participants’ answers to philosophical thought experiments. This resulted in reasonable success. The top performing model achieved approximately 78% accuracy. The strongest predictor variable was whether participants committed the bypassing error when reasoning about determinism.

Next, we provided the models with only participants’ cognitive-trait profile. We found that neurodiverse traits were more predictive than responses to thought experiments when it came to whether a participant was a philosopher or non-philosopher. The strongest predictor traits were representational manipulation, visual imagery, and ADHD symptoms. Using just these three traits, the classification accuracy was 81%. In short, if we choose someone at random from our study and we want to determine whether that person has studied philosophy, we could just use responses to the scales for measuring visualization, representational manipulation, and AHD to make reliable predictions that are quite significantly above chance.

Lastly, we asked the models to use both types of information (that is, responses to thought experiments and neurodiverse traits. By combing the two, the classification-accuracy of the models went up to 86%. The three best predictors for this mixed model were scores on bypassing, representational-manipulation, and visual imagery.

In closing, I just want to point out that our study had several limitations (e.g., it relied on self-report) and it also left several unanswered questions (e.g., we can’t speak to whether philosophy attracts people with certain cognitive styles or whether philosophical training influences cognitive style). You can find our discussion of these limitations (and more detailed discussions of our findings) in our full article. But because Justin was kind enough to post our call for participants on Daily Nous and many readers took the time to complete the survey, I thought I would share the results.

[1] It’s worth emphasizing that we were examining traits (measured via scales), not attempting to diagnose participants with autism spectrum disorders, ADHD, aphantasia (“mind blindness”), anendophasia (no internal dialogue), etc.

[2] This trait is not normally considered to be a neurodiverse trait; however, scores on the scale measuring this construct are significantly correlated with several of the neurodiverse traits listed above.

[3] We also found that other cognitive characteristics similarly correlated with philosophical judgments. However, due to space constraints, I will refrain from detailing them here (those interested can check out the paper).