If you are with a group of > 4 friends and you want to choose between an empty train or a moderately occupied one, pick the latter if you want to talk during the journey. Because chances are, if there are seats, and if all of you sits down in a row, you would leave the social world and be transported to your own private digital world.
If there are no seats, you and your group of friends will be forced to stand around, and usually, your group will end up standing in a circle. Standing in a circle doing nothing, looks awkward right? This exerts pressure on the people in your group to start a conversation. Moreover, standing in a circle makes it easy to maintain eye contact, which is an important element in communication.
However, when there are seats, and your group consists of more than 4 people, chances are once you hit the seat, you will indulge in your own digital devices such as ipod, psp and books etc. The following picture says it all (FYI the group of derpinas all know each other and we went to the train together about 3 minutes before this shot was taken).
Even if you brought nothing, being seated in a row makes it awkward to engage in a conversation with the whole group.
The exception is when there are 4 or less people.
When there are 2 people, obviously it doesn’t matter whether you’re seated or standing, because it is convenient to face the other person when seated.
When there are 3 people, it is still acceptable to engage in a conversation because the person at each side can face the centre. However, the middle party may get a neck-ache trying to face the person speaking all the time.
4 people will really be pushing the limit, not that it is not possible, but more likely than not, the group will be split into groups of 2, each lost in their own conversation.
The way to prevent this is to not have everyone seated. That is have some stand in front of those who sat. That way, everyone can still maintain eye contact. However, the people seating might feel a little abated for sitting.