Don't ask the barber if you need a haircut — a simple reminder that asking someone with a vested interest in the outcome isn't likely to give you an impartial answer.

Except that while we might reasonably make decisions about our hair with few consequences to anyone but ourselves, when we work with professionals they may well see or hear what we don't. It might be that asking a professional to review what you're doing is exactly what you need to tell you what you didn't and couldn't think to ask.

The phrase has been famously shared by Warren Buffet though it appears in several similar earlier forms.

Don't ask the barber if you need a haircut

The Rhyme As Reason Effect suggests that we're more likely to consider something as accurate or truthful when it rhymes. In a lovely study that asked people to consider the accuracy of both rhyming and non-rhyming aphorisms, "Woes unite foes," or "What sobriety conceals, alcohol reveals," for example, were considered more accurate than "Woes unite enemies," or "What sobriety conceals, alcohol unmasks."

A classic example outside of old sayings is OJ Simpson's trial where the defense attorney memorably noted "If the gloves don't fit, you must acquit!"

You can read the study in the delightfully titled paper, Birds of a feather flock conjointly: Rhyme as Reason in Aphorisms (pdf), by Matthew McGlone and Jessica Tofighbakhsh.

In a related note I was always curious how "Beer before wine, you'll feel fine," tallied up with what I heard in the US: "Beer before liquor, never been sicker," or even "Grape or grain but never the twain." It turns out from a neat 2019 study that, whichever way round you rhyme them, they have no effect on your hangover despite how persuasive the Rhyme As Reason effect may be — even after a few beers.

The Rhyme As Reason Effect

Sankey diagrams are handy ways to visualise material or energy flows through usage and time. They are excellent for displaying energy source and usage, for example the UK government publishes a Sankey diagram of UK energy each year (pdf).

Perhaps the most famous example is Charles Joseph Minard's remarkable visual showing Napoleon's invasion of and retreat from Russia in the Winter of 1812–13. In that chilling example the thickness of the lines represent the remaining size of Napoleon's army.

I learned about Sankey diagrams from Edward Tufte but perhaps people see them most commonly today in Google Analytics showing the different paths visitors take on a website before leaving.

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Sankey diagram