In 1994 Monk and friends investigated why people on mobile phones are annoying. You know what I'm talking about. When you're sitting on a train just minding your own business and you heard the dingle-dingle of someone's phone and you just know you're going to hear all about someone's baby / Saturday night / shopping list / job. FSM, that's annoying. Seriously, when my phone rings I keep it as quick and as quiet as possible, often returning the call as soon as I'm in a more appropriate setting. On a side note: I'm so glad we no longer have novelty ring tones. Did you ever hear the female orgasm one go off in a public space? Yeah, good one buddy. You and your mate might think that's cute on the work site, but on a bus it's another story...

Anyway, Monk and friends (1994) investigated why this was so damn annoying. Was it due to the volume of the speaker? Are mobile phones just more salient (attention capturing) than normal conversations? Do people have biases against people who publicly use mobile phones? Or was it something else?

By cleverly staging a  conversation on a train (or at a bus stop), either with one person on a mobile phone, or with two people in situ, then asking folks nearby to give rating regarding volume, intrusiveness, content, salience and capturing (i.e. 'I found myself listening to the conversation') they were able to tease out the situation. It turns out that

the thing that pisses us off most is the fact we only hear one side of the conversation. They inferred this because the main effects of volume wasn't significantly different between conversations, nor was intrusiveness, or content. People, however, did find themselves drawn into one-sided mobile phone conversations more. Now there was some complicated interactions, such that results differed slightly when people were on phones (and rated on intrusiveness or salience), but the main effects (the big, over-arching things) were absent.

This effect was later replicated by Monk and (some different friends) later that year. This time they added a third condition - a face-to-face conversation in which only one side of the conversation was audible [the methods are not clear how they exactly made this happen]. Yet, they found similar results in the one-sided face-to-face condition as they did in the phone condition.

They argue that is has something to do with hearing only one side of the conversation, and being drawn into it because it's not complete. There's not a lot of theory behind it, I must admit it (at least expressed in the paper) but they suggest the mechanism at play is the same mechanism that is active when we hear a question.

Perhaps this commitment to understand is in some way automatically triggered when hearing only
one side of a conversation. For example, hearing a question could be particularly intrusive if one does not
immediately hear the answer of the other person.

- Monk, Fellas & Ley (1994b)

Part of me wants to offer an alternate idea. Spoken language must, in many ways, share elements with written language. Now we're very good at not paying explicit attention to the world around us. People might be chatting, writing, jogging, waiting, kissing, or begging and we can walk right past and never give it a second thought. We may register it at the time, but we file it in the mental category of 'not relevant to me'. Sometimes you might hear your name (by coincidence) or something that you know, like a Bar or Street, or a Location, and you immediately tune back in, with varying levels of prior comprehension. Yet their may exist a contrast with a one-sided conversation. Think of a time when you say two businessmen on a train chatting - what were they talking about? Now think of a time you saw someone (audibly) mumbling/talking to themselves - what was s/he talking about? My guess is that you can pull snippets about the mumbler, but not the businessmen. I know I can.

So here's a written analogue. It's called a stroop task. The idea is to as quickly as possible name the colour of the ink the text is written in, from top to bottom, column by colum. Try it:

It's really quite challenging. It's based on the fact that we humans (at least those of us who can read) are so practiced at reading that when presented with a word it's an explicitly difficult operation to suppress that ability.

I reckon something similar is going on, that's why we're drawn in. We understand language, and we frequently filter out anything that's not relevant to us. Half because it's not relevant, but half because it's totally expected, banal and predictable.

If I'm right that leads to a bunch of interesting hypothesis.

1) Unpredictable conversations (even when we can hear both sides) are more intrusive than predictable ones. Think of a public argument you may have witnessed, even one that wasn't especially loud. Could you tune it out?

2) Conversations that don't make sense to you are harder to tune out. I know I can talk some world-class bullshit with my friends, replete with obscure in-jokes and tangential references. Is that more intrusive and salient that a conversation between two businessmen, all other things constant?

3) How about a totally mundane conversation, but with certain key-words (say, all proper nouns) expressed in a different language, or even code. Suddenly something barely worth your attention (and likely still is unworthy) has an unpredictable element. Can you tune it out?

Here, of course, I'm talking about salience, not about annoyingness. Perhaps these conversations are annoying (particularly 2, and to some extent 1), but I bet they register high on the explicit measure of 'I found myself listening to the conversation' which was Monk's DV (Dependent Variable, or, explicit measure of effect). What about you? Have I missed the point? Is my mechanisms wrong (that it's difficult to suppress attention when are hard-wired comprehension module is violated)? What other findings does this infer?

In the mean time, the next time you see some dick with a mobile phone, try to guess what they're talking about. Maybe you could introspect a little and workout if it's more (or less) annoying depending on their topic. Maybe if they're talking about dinner and you're a foodie you're less bothered than if you're a foodie and they're talking about rock-climbing. My guess is that the better you comprehend the one-sided conversation, the less it bothers you... 

Monk, A., Fellas, E., & Ley, E. (2004). Hearing only one side of normal and mobile phone conversations Behaviour & Information Technology, 23 (5), 301-305 DOI: 10.1080/01449290410001712744 Monk, A., Carroll, J., Parker, S., & Blythe, M. (2004). Why are mobile phones annoying? Behaviour & Information Technology, 23 (1), 33-41 DOI: 10.1080/01449290310001638496