Science of Doubt: The Left-Hand Experiment

How your tools might kill your confidence?

In 2003, researchers asked their students to write down their BEST or WORST qualities.


“It’s a graphology study,” they said.

(it wasn’t)


They asked some students to write with their dominant hand.

So right hand for right-handers.

And they asked other students to write with their non-dominant hand.

So left hand for right-handers.


Once they were done, the researchers asked each student to rate how confident they were about the qualities they just wrote down.

For example:

𝐼 𝒢𝓂 π‘”π‘œπ‘œπ’Ή 𝒢𝓉 π“Œπ“‡π’Ύπ“‰π’Ύπ“ƒπ‘” π’Έπ‘œπ’Ήπ‘’. 𝐼’𝓂 7𝟒% π“ˆπ“Šπ“‡π‘’ π’Άπ’·π‘œπ“Šπ“‰ π“‰π’½π’Ύπ“ˆ.

𝐼 𝒢𝓂 𝒷𝒢𝒹 𝒢𝓉 π“ˆπ“…π‘œπ“‡π“‰π“ˆ. 𝐼’𝓂 𝟫𝟒% π“ˆπ“Šπ“‡π‘’ π’Άπ’·π‘œπ“Šπ“‰ π“‰π’½π’Ύπ“ˆ.

α΅’ β‚β‚˜ gβ‚’β‚’d β‚β‚œ dᡣₐwα΅’β‚™g. α΅’’β‚˜ 5β‚€% β‚›α΅€α΅£β‚‘ ₐbβ‚’α΅€β‚œ β‚œβ‚•α΅’β‚›.

α΅’ β‚β‚˜ bₐd β‚β‚œ ₗₑₐdα΅’β‚™g ₐ β‚œβ‚‘β‚β‚˜. α΅’’β‚˜ 4β‚€% β‚›α΅€α΅£β‚‘ ₐbβ‚’α΅€β‚œ β‚œβ‚•α΅’β‚›.


The researchers had a pile of self-evaluation scorecards.

Some were written “badly”; others were written correctly.

Can you guess what they found?


People using their dominant hand were more confident about their thoughts!

(for positive AND negative thoughts).

I find the idea that “simply” using the wrong hand can change how you perceive yourself to be… astounding.

So here is a question for you:

🧰 What might be the impact of your tools on how confident you are about your work?

πŸ“œ Source:

BriΓ±ol P, Petty RE. Overt head movements and persuasion: a self-validation analysis. J Pers Soc Psychol. 2003 Jun;84(6):1123-39.

doi: 10.1037/0022-3514.84.6.1123. PMID: 12793580.

Laurent Senta

I wrote software for large distributed systems, web applications, and even robots. These days I focus on making developers, creators, and humans more productive through