Dunning-Kruger effect

The Dunning–Kruger effect is a cognitive bias in which "people reach erroneous conclusions and make unfortunate choices but their incompetence robs them of the metacognitive ability to realize it". The unskilled therefore suffer from illusory superiority, rating their own ability as above average, much higher than actuality; by contrast the highly skilled underrate their abilities, suffering from illusory inferiority. This leads to a perverse result where less competent people will rate their own ability higher than more competent people. It also explains why actual competence may weaken self-confidence because competent individuals falsely assume that others have an equivalent understanding. "Thus, the miscalibration of the incompetent stems from an error about the self, whereas the miscalibration of the highly competent stems from an error about others."

"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt." - Bertrand Russell

Hypotheses
The phenomenon was demonstrated in a series of experiments performed by Justin Kruger and David Dunning, then both of Cornell University. Their results were published in the Journal of Personality and Social Psychology in December 1999.

Kruger and Dunning noted a number of previous studies which tend to suggest that in skills as diverse as reading comprehension, operating a motor vehicle, and playing chess or tennis, "ignorance more frequently begets confidence than does knowledge" (as Charles Darwin put it). They hypothesized that with a typical skill which humans may possess in greater or lesser degree,
 * 1) Incompetent individuals tend to overestimate their own level of skill.
 * 2) Incompetent individuals fail to recognize genuine skill in others.
 * 3) Incompetent individuals fail to recognize the extremity of their inadequacy.
 * 4) If they can be trained to substantially improve their own skill level, these individuals can recognize and acknowledge their own previous lack of skill.

The authors draw an analogy with anosognosia – a condition in which a person who suffers a physical disability due to brain injury seems unaware of or denies the existence of the disability. This may include unawareness of quite dramatic impairments, such as blindness or paralysis.

Possible applicability to climate contrarianism
Many climate contrarians lack a grounding in college and graduate level science coursework and research. This means they won't have had the feedback that students in a teacher-student relationship get, regarding their scientific abilities and intuitions. The Dunning-Kruger hypothesis suggests that people without such feedback are more likely to be overconfident in their self-assessments of ability.

Studies
Kruger and Dunning set out to test their hypotheses on human subjects consisting of Cornell undergraduates who were registered in various psychology courses. In a series of studies, they examined self-assessment of logical reasoning skills, grammatical skills, and humor. After being shown their test scores, the subjects were again asked to estimate their own rank, whereupon the competent group accurately estimated their rank, while the incompetent group still overestimated their own rank. As Dunning and Kruger noted, "Across four studies, the authors found that participants scoring in the bottom quartile on tests of humor, grammar and logic grossly overestimated their test performance and ability. Although test scores put them in the 12th percentile, they estimated themselves to be in the 62nd."

Meanwhile, people with true knowledge tended to underestimate their competence. A follow-up study suggests that grossly incompetent students improve both their skill level and their ability to estimate their class rank only after extensive tutoring in the skills they had previously lacked.