Thinking critically is tough, and the prime minister is not alone in failing to do it, says Victoria University academic Matt McCrudden.
In 2012 the BBC grilled John Key about the "100% Pure" tourism brand after freshwater scientist Mike Joy declared New Zealand was "delusional about how clean and green we are".
Mr Key responded by dismissing academics as being like lawyers with an opinion for hire. "He's one academic and, like lawyers, I can provide you with another one that will give you a counterview," he said.
Dr McCrudden says: "Here Key is essentially saying that all evidence is equivalent - you just need to find a source who supports your view. However, it does not change the amount of runoff in our waterways."
Dr McCrudden has embarked on a series of studies looking at the way beliefs and attitudes feed preconceived ideas, with a view to finding out how scientists and other educators can get students to think more rationally by divorcing beliefs from reasoning.
"When people read ideas that are similar to their own, they often conjure up thoughts that support what they are reading.
"But when people read ideas that conflict with their ideas, they tend to try to refute that information. That is, we tend to be more critical of ideas that challenge our beliefs. This is normal."
But this very human quirk can be problematic.
"Effective critical thinking is the ability to evaluate information independently from one's beliefs. However, effective critical thinking can be a challenge if people discount or dismiss information consistent or inconsistent with their beliefs."
In his study, 68 high school pupils read weak and strong evidence for the existence of climate change. Fourteen were opposed and the rest agreed - and he found differences in interpretation could largely be put down to the reader's preconceived beliefs.
People's biases often came into play when they were gauging information on which they already had an opinion, but he also found some in the sample made very balanced evaluations.
The finding was reinforced by another study, in which he examined how the students judged information about climate change.
People with conflicting attitudes on climate change used the same data - that in Sydney in 2013 the average temperature in October was 22 degrees Celsius, whereas in 2012 it was 21C - to support their point of view.
The difference between climate and weather was a matter of time, so judging climate change on a single weather event - weak evidence - was akin to basing the height of all Wellingtonians on a person who had just got off a bus, Dr McCrudden said.
Cherrypicking weather events was used by corporate-backed lobby groups in the United States to sway public opinion over the negative implications of human-induced climate change, whereas the evidence for it was agreed upon by 97 per cent of climate scientists, he said.
- The Dominion Post
What should happen with the Zephyrometer?Related story: Wind wand's future up in the air