September 08, 2006

What's the frequency, Kenneth?

About a decade ago, I began to encounter a surprising number of well-groomed mentally ill people wandering around talking to imaginary companions. Of course, it turned out these people were talking on cell phones with earbuds and microphones. Now, hands-free cellular telephony is so normal that I sometimes encounter slightly scruffy people who seem to be using a bluetooth headset, until it turns out that they're tuned in to a completely internal service provider, offering an unlimited number of anytime minutes per month. So I was amused to see this cartoon a couple of weeks ago:

The cartoon brings out something that I've often wondered about. Cell phone conversationalists sometimes use hand gestures and head-and-and-face movements. Why? And how does this compare to what they would do if their interlocutor was physically present?

In the cartoon, it looks like only one cell phone speaker -- the second from the left -- is gesturing, and none of the speakers seems to be modulating their head position and facial expression (unless those odd hooded eyes are supposed to be some kind of communication-related behavior.) My informal observation -- and it's easy to get lots of data, walking across the Penn campus -- is that hand gestures are rare, but a certain amount of head-and-face-wiggling seems to be pretty automatic. At least, you see lots of cell phone speakers with eyebrows going up and down, heads nodding and shaking and posing, etc. Yesterday, for example, someone walking towards me, deep in conversation with an etheric companion, said "um, I don't know", and furrowed his brows while moving his head to look up and to the right, as people sometimes do to signal that they're searching their memory.

The obvious thing that's got to be missing, I guess, is shifting gaze towards or away from the person you're talking to. You can't look someone in the eyes -- or avoid their eyes -- if they're not there. But otherwise, the whole package of gestures and expressions and postures seems to be in play, at least sometimes.

This highlights a puzzle about meaning. When people communicate, they do a lot of things that seem cleverly calculated to influence the knowledge and beliefs of others. The calculations behind these actions represent what psychologists call "theory of mind" reasoning, and they seem to involve a complex and many-layered logical analysis of the beliefs and goals of the speaker and hearer, the nature of the context, and general assumptions about the cultural norms of communication. Philosophers and linguists often refer to this kind of calculation (especially when conversational norms are involved) as "Gricean"; and they generally assume that speakers and hearers are actively carrying it out all the time. Conversation, on this view, is a sort of interactive cascade of theorems.

The first aspect of this puzzle, I guess, is how in the world people who show no signs of being able to apply simple logical reasoning in other cases can be so extraordinarily good at acting out theory-of-mind theorems. Evolutionary psychologists tend to take this as evidence for "modularity" -- humans, on this view, have evolved a specialized cognitive module -- perhaps even a specialized brain circuit -- for theory-of-mind reasoning, which is "encapsulated" and thus not available for theorem-proving in other areas.

However, many theory-of-mind calculations are obviously not carried out in real time, so to speak, but instead represent the application of communicative habits that are more-or-less well matched to the needs of the context. You can see that especially clearly in the case of gestures, whose connections to the content of speech can certainly be treated in terms of the logic of communication, but which continue to be used to some extent even when the person you're talking to can't see them.

Perhaps there's no real puzzle here -- people chatting in a bar are proving theorems only in the sense that the planets whirling in their orbits are solving differential equations. But I'm not sure.

[David Nash writes:

My off the cuff reaction is that flicking the eyes up and to the right like this feels like a help to memory retrieval, and isn't intended as a signal to someone else.

Maybe so -- I believe that I've heard claims about this, and maybe even some stuff about when people look right vs. left while trying to remember. The thing is, I don't think that I do this when I try to recall something while writing or programming, though I definitely do it when conversing, whether face-to-face or on the phone. Of course, intuitions about the distribution of such behavior are not very trustworthy.]

[Ben Zimmer suggests that I should offer our less clueful readers a link to the background of the "What's the frequency, Kenneth?" quotation.]

Posted by Mark Liberman at September 8, 2006 07:26 AM