In American culture, a thumbs up is a sign of approval and confidence. Why? Where did that come from? Of all the fingers, why that one?
It seems that before the thumbs up as the "all OK" sign, someone had to invent it. It seems like it was popularized by American pilots in WWII. As the story goes, the pilots and ground crews would flash thumbs up to signal that the planes were ready to roll off the airstrip and into combat. Since then, it's become an inseparable part of American idiomatic body language and is spreading overseas with the rest of American culture.
Joe Navarro points out in his book What Every Body is Saying that the thumbs up may be wired into us as a display of confidence.
Besides the ubiquitous and consciously made thumbs-up, we humans use the display of our thumbs in a wide variety of circumstances to illustrate confidence, or if we hide our thumbs, the lack of it.
Navarro points to these examples, which I encourage you to try out for yourself:
Wonderful, you say; I'll immediately go practice my thumb posture in front of a mirror.
This is very interesting, but in this article I'm more concerned about answering why the thumbs-up (even subconsciously made) almost universally indicates a show of confidence. Why the thumb? Does it all stem with the consciously-made thumbs-up gesture popularized during WWII, or does it go back further than that?
My hypothesis is that it is because the thumb is representative of the human creative faculty. The opposable thumb is what sets him above and apart from the rest of the Kingdom Animalia. The opposable thumb allowed us to develop creativity, which means we can make the tools and institutions necessary to conquer, subjugate, and master our environs and our neighbors.
Leonard Shlain, in Leonardo's Brain, writes (p.122):
There is only one species that can ask a question and- most impressively- dispute the answer. That appendage [that makes it possible] was the opposable thumb. Thumbs have a lot to do with curiosity, which in turn leads to creativity... Bestowing language on a creature that does not possess the means to answer the questions it has posed would be uneconomical. The opposable thumb provides Homo Sapiens with the critical appendage.
In the same way that the middle finger came from medieval archers taunting their foes (as the story goes, captured archers had their middle fingers cut off to prevent them from ever drawing a bow again- so to give an enemy the middle finger was to communicate that you were unbeaten and able to fight), giving the thumb communicates (rather less combatively than the middle finger) that we still possess the fundamental evolutionary innovation we need to manipulate the world and mold it to our image.
Why else would we refer to the weak as being "under the thumb" of the strong?
So thumbs allowed human beings to display curiosity, and creativity. It seems logical to think that this could explain why a thumbs-up has since become a sign of confidence: the thumb is the original instrument of mastery over the natural world.
Navarro isn't able to explain why the thumbs-up communicates confidence, and I don't recall ever reading an explanation in other sources. My theory came to me while reading Leonardo's Brain. I don't know if others have written about this or not. Even if it turns out that I'm wrong and am reading too much into the humble thumbs-up, I hope I'll continue to think of the gesture as an expression of the fundamental capacity a human being has to forge his own way and shape the world in his image.
With a big thumbs-up,
Dillon Dakota Carroll
...sees much and knows much