Here's a simple experiment. First bend over so your torso is parallel to the ground, like an aircraft fuselage. Now imagine the aircraft doing a partial barrel-roll. You can't move your torso much that way, but you can move your head. When you are oriented in the normal upright position, that head-roll is, in Western culture, a gesture that means "no".
Next, back to bending over; the second primary aircraft motion is called "pitch", and that's what a plane does when it dives or ascends. You can move your head like that, too, and when you are oriented upright, this gesture, in Western culture, means "yes".
The third primary aircraft motion is called "yaw". It leads to either a left turn or a right turn. To move your head this way, you would try to place your ear on a shoulder (without moving the shoulder). If you did this from side to side, this would be a distinct gesture different from either "yes" or "no", and yet Western culture does not seem to have assigned a particular meaning to it.
How about "maybe"?-- Vernon, Jan 04 2010 heheheh [+]-- FlyingToaster, Jan 04 2010 Doesn't it already have that connotation on the Indian sub-continent? [EDIT] Thinking back, I seem to remember it has that meaning too in France ("comme ci, comme ça"), which leads to the inevitable "invented by someone French" (however, this can be countered by assuming that France isn't part of "Western culture").-- coprocephalous, Jan 04 2010 I thought it meant stiff neck.-- The_Saint, Jan 04 2010 oh that's relieved my stiff neck, thanks vernon.-- po, Jan 04 2010 Using this same technique, you can achieve satisfaction in elimination while on the jon. Old Chinese technique.......+....... Third motion quaranteed.-- outloud, Jan 04 2010 Actually, I would describe motions in terms of the torso in its normal position, in which case a "nod" is pitch, a "no" is yaw and this third movement would be "roll".
But, as noted, roll is quite widely used already. As an aside, the relationship between yes/no and nod/shake is not universal: a colleague of mine shakes his head for yes, and nods for no.-- MaxwellBuchanan, Jan 04 2010 [MaxwellBuchanan], if your colleague is from a non-Western culture, then that's why I specified the culture in the main text.-- Vernon, Jan 04 2010 I would concur with [coprocephalous] that it is used with this meaning, and various others, in people of South Asian descent or culture.-- nineteenthly, Jan 04 2010 I'm told that in some places (perhaps parts of India? I don't remember) the third, side-to-side head wobbling motion means "I'm thinking about it", much like in the UK we might say "Errrrrrr..." or "Ummmm..." before actually starting to reply.-- Wrongfellow, Jan 04 2010 //I specified the culture// Ah yes, so you did - apologies. However, I do see Westerners using this movement when they are undecided (usually whilst saying a long "Hmmmm").-- MaxwellBuchanan, Jan 04 2010 There are two different movements here: you can either roll your head from side to side, so it tilts left and then right; or you can slide your head side to side so it remains level.-- pocmloc, Jan 04 2010 That's true. By the same token, there are a total of six basic movements (roll, yaw, pitch, fore-back, left-right, up- down).
Given that they can be combined pairwise (at least), there should be a very much larger repertoire of compound movements. For example, a combination of pitch (nodding) and yaw (head shake) leads to a variety of movements, depending on the rate, phase and amplitude of the two components. (Eg, the nose can describe a circle, a diagonal, the other diagonal, figure of 8, etc).
Some options would probably require novel anatomy.
Maybe we should start a YouTube-based competition to see who can demonstrate the greatest repertoire of compound head movements?-- MaxwellBuchanan, Jan 04 2010 // would probably require novel anatomy //
Perhaps not, but they might turn out to be one-time-only actions........-- 8th of 7, Jan 04 2010 In Bulgaria, 'Yes' and 'No' are reversed between the nod and shake.-- RayfordSteele, Jul 25 2011 random, halfbakery