"It's not rocket science" is a phrase usually used to suggest that a task or concept is not actually so difficult but fairly simple to do or understand.

But a new study suggests aerospace engineers and brain surgeons are not necessarily brighter than the general population - and that a career in either field is within anyone's reach if they apply themselves.

Researchers compared the intelligence of 329 aerospace engineers, 72 neurosurgeons - recruited through the internet from across the UK, mainland Europe, the US and Canada - and 18,257 members of the British public.

The participants were asked to complete 12 tasks online using the Great British Intelligence Test (GBIT) from the Cognitron platform, along with questions related to their gender, age, where they live, and level of experience in their speciality.

The tasks examined aspects of cognition, spanning planning and reasoning, working memory, attention, and emotion-processing abilities.

The study pointed to a sketch by British comedians David Mitchell and Robert Webb during which a boastful neurosurgeon is put in his place by a rocket scientist who says: "Brain surgery... it's not exactly rocket science is it?"

Researchers said the purpose of the study - in part - was to settle this debate once and for all - and question whether public perceptions of rocket science and brain surgery were borne out in reality.

Their findings of their assessments suggest that contrary to belief, there were little difference between the intelligence of neurosurgeons, aerospace engineers and the general population.

Aerospace engineers and neurosurgeons were equally matched. However, aerospace engineers scored higher when assessed on their attention and mental manipulation abilities, whereas neurosurgeons were better at semantic problem solving, such as defining the meaning of rare words.

Neurosurgeons were able to solve problems faster than the general population but showed a slower memory recall speed, the findings suggested

Comparing their results to the general population, aerospace engineers did not show significant differences in any areas.

Neurosurgeons were able to solve problems faster than the general population but showed a slower memory recall speed.

"These results suggest that, despite the stereotypes depicted by the phrases 'It's not rocket science' and 'It's not brain surgery', all three groups showed a wide range of cognitive abilities," researchers said.

"It is possible that both neurosurgeons and aerospace engineers are unnecessarily placed on a pedestal and that 'It's a walk in the park' or another phrase unrelated to careers might be more appropriate," they concluded.

"Other specialties might deserve to be on that pedestal, and future work should aim to determine the most deserving profession."

Researchers also said they hoped the findings would help dispel the misconceptions surrounding the perceived difficulty and skillset required for both professions - which are also seen traditionally as "masculine" disciplines.

"Our results highlight the further efforts required to widen access to these specialities to mitigate impending staff shortages and ensure a diverse workforce to drive future innovation," they said.

The study, published in the BMJ, was approved by the University College London research ethics committee and supported by the Society of British Neurological Surgeons and the UK Space Agency.