<p>The extensive forms of the signalling game and the twice-repeated prisoner's dilemma have the depicted specific shapes (showing who decides what in which sequence having which information) because this is how these games are defined.</p>
<p>The first is drawn with the root in the middle and the second with the root on top, because that's the clearest way to arrange the decision nodes while avoiding (graphically) intersecting information sets.</p>

CC BY-SA 4.0
2023-06-02T08:17:24.813Z
2023-06-02T08:17:24.813Z
VARulle
<p>Is there any reason for the differing shapes of game trees when we use extensive form representation? For instance, why does the job market signalling game and the repeated Prisoner's Dilemma take the specific extensive forms as under?</p>
<p><a href="https://i.sstatic.net/ONAEL.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ONAEL.jpg" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2023-06-01T13:51:37.063Z
Is the question why they have this specific extensive forms or why they are drawn this way on a two-dimensional surface?
Michael Greinecker
CC BY-SA 4.0
2023-06-01T17:05:08.813Z
Why have they this specific extensive forms? As in, are there any underlying assumptions for the same?
S.G.
CC BY-SA 4.0
2023-06-01T18:21:19.620Z
These are really two different questions. Why is each of these extensive forms modeling the particular economic problem?
Michael Greinecker
CC BY-SA 4.0
2023-06-01T20:08:01.537Z
Yes Sir, that forms one part of the question. But why does it also not necessarily imply under what assumptions the above forms will be used? To model the games above wouldn't a specific extensive form be used only under certain assumptions?
S.G.
<game-theory><dynamic-games>
Extensive Form of Games
S.G.
# Extensive Form of Games

(Asked by: username_0 on 2023-06-01)

Is there any reason for the differing shapes of game trees when we use extensive form representation? For instance, why does the job market signalling game and the repeated Prisoner's Dilemma take the specific extensive forms as under?

[![enter image description here](https://i.sstatic.net/ONAEL.jpg)](https://i.sstatic.net/ONAEL.jpg)

**Tags:** game-theory, dynamic-games

> **Comments:**
> **username_1**: Is the question why they have this specific extensive forms or why they are drawn this way on a two-dimensional surface?  
> **username_0**: Why have they this specific extensive forms? As in, are there any underlying assumptions for the same?  
> **username_1**: These are really two different questions. Why is each of these extensive forms modeling the particular economic problem?  
> **username_0**: Yes Sir, that forms one part of the question. But why does it also not necessarily imply under what assumptions the above forms will be used? To model the games above wouldn't a specific extensive form be used only under certain assumptions?  

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## 1 answers

### Answer by username_2 on 2023-06-02. Score: 2

The extensive forms of the signalling game and the twice-repeated prisoner's dilemma have the depicted specific shapes (showing who decides what in which sequence having which information) because this is how these games are defined.

The first is drawn with the root in the middle and the second with the root on top, because that's the clearest way to arrange the decision nodes while avoiding (graphically) intersecting information sets.


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