In this paper we want to describe some of the constraints that restrict the interlocutors' freedom at the logical level during spontaneous conversation (these are not necessarily conscious of such constraints). This claim may be surprising, since it is not usual to consider daily conversations as heavily constrained. Admittedly one cannot say anything when involved in a conversation : everybody has experienced the trouble caused by an abrupt topic change, provoking reactions like "What does it have to do with what we are saying?" or reactions showing misunderstanding ("remedial responses"), as shown in experiments performed by Vuchinich [1980]. But one should not forget that there are many other constraints, as, for instance, the following excerpt reveals:
[ex_lunch]
context: A had a special lunch at his workplace, as is usual just before Christmas, and thought B had too.
A1- Et toi, a va? Tu as bien mangé, à midi?
B1- Pourquoi tu me demandes a?
A1- And you, are you okay? Did you have a good lunch?
B1- Why do you want to know?
B's reply was pronounced like a protest. A question like A1 does not seem to be admissible out of context, as it was the case at the beginning of this conversation. Every time we observe a question like "Why do you want to know?", or some aggressive reaction showing a failure to understand the intended meaning of the last utterance, we may conclude that some conversational rule has been violated. In the following excerpt, the protest is expressed first through a grimace, and then by a sarcastic question:
[ex_train]
context: A (the author) comes home everyday by train. He utters A1 intentionally as an experiment, to observe B's reaction.
A1- J'ai pris le train.
B1- [grimace]... c'est un exploit?...
A1- I came by train
B1- [grimace]... Is that such a great feat?...
In these examples, the conversational problem arising between both speakers cannot be the consequence of any misunderstanding. In the first excerpt, it would have been easy for B simply to give the information required. B actually never did so during the rest of the conversation. In the second one, B could have simply acknowledged the very simple statement A1. This may indicate, if necessary, that spontaneous conversation is not a mere exchange of information, but another kind of game, a much more complex one, with its own rules.