convert extensive form to strategic form

So basically when you convert a sequential game from extensive form to normal form, it becomes another game where you then look for Nash equilibria. 0000012609 00000 n There are two basic types of interactions: • Sequential: Players make alternating moves • Simultaneous: Players act at the same time The interaction in the cartoon is purely sequential and we can 0000013541 00000 n c) Find all of the pure-strategy Nash equilibria of this game using any method. equilibria for the extensive form. 0000002226 00000 n 0000002568 00000 n d) Identify which of the Nash equilibria you found in c) are subgame-perfect Nash equilibria. 0. 203 0 obj << /Linearized 1 /O 205 /H [ 908 1158 ] /L 114605 /E 23235 /N 52 /T 110426 >> endobj xref 203 23 0000000016 00000 n And that is that we can convert an extensive-form game into the normal form and there are a couple of reasons why this is interesting. Both forms of representation are useful in their on way, and I will use both representa 1.1 Selten’s Game However, some of these equilibria would have important drawbacks because they ignore the dynamic nature of the extensive-form. endstream endobj 213 0 obj << /Filter /FlateDecode /Length 7062 /Subtype /Type1C >> stream H��V�n�F��+x�L��q�1ۘ��90%1��_�?�WUMI� �H��j{տ7��{��Y/�$�>+�`��̓`BlRx��I��fq��$�q�gyn}�,�y^|S��U�U<7:u�Ϝ�:i:N�T�.�O�;m�Rm�˂�%4�*3��u�iQ|�c��-ՓN Q��UQe�W�^[��]��>��&ͧE��9��9�ZZd^�P�r�C�d�Խ��8��!� P��=��K��(lH�3O�+�P$E��*�4�t�74]��꺪!=��+��؜��B��V�#�#@"�A�`�Hy1z8W��!劔I� %��N��d=B��E�fqW��Q��eh�u�evi��X�O��=< +NGN�v�U��B��\��nٯٹ��mKut� :�-�"2�]J�qr��Y*C��~��}\�\y�� q�K��^�BF'ɢB��^��AȄL$i�i�v��fp�Pl4^��CgX>$�ps��Z��L`Η�bȥN�h=�Dv�|�y@ ��'׻; ��n�(�� yy�%�=�k�@-�V;�DW�kZ��5�`L��~`�^辱�&Z��͚�8��Ц"��8�"f��پ�$��ݒ��#p�� ̃�/ endstream endobj 225 0 obj 1039 endobj 205 0 obj << /Type /Page /Parent 194 0 R /Resources 206 0 R /Contents 212 0 R /MediaBox [ 0 0 612 792 ] /CropBox [ 0 0 612 792 ] /Rotate 270 >> endobj 206 0 obj << /ProcSet [ /PDF /Text ] /Font << /F1 211 0 R /F2 208 0 R /F3 216 0 R /F4 219 0 R >> /ExtGState << /GS1 221 0 R >> >> endobj 207 0 obj << /Type /Encoding /BaseEncoding /WinAnsiEncoding /Differences [ 19 /Lslash /lslash /minus /fraction /breve /caron /dotlessi /dotaccent /hungarumlaut /ogonek /ring /fi /fl ] >> endobj 208 0 obj << /Type /Font /Subtype /Type1 /FirstChar 21 /LastChar 215 /Widths [ 778 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 500 0 500 0 0 0 0 0 0 0 0 0 0 0 500 0 500 500 0 0 0 0 500 0 0 0 0 0 0 0 500 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 778 ] /Encoding 207 0 R /BaseFont /LPCNPA+CMSY10 /FontDescriptor 209 0 R >> endobj 209 0 obj << /Type /FontDescriptor /Ascent 0 /CapHeight 0 /Descent 0 /Flags 96 /FontBBox [ -29 -960 1116 775 ] /FontName /LPCNPA+CMSY10 /ItalicAngle -14.035 /StemV 85 /StemH 40 /CharSet (/bullet/multiply/minus) /FontFile3 222 0 R >> endobj 210 0 obj << /Type /FontDescriptor /Ascent 693 /CapHeight 0 /Descent -200 /Flags 262178 /FontBBox [ -53 -251 1139 750 ] /FontName /LPCNOF+CMBX12 /ItalicAngle 0 /StemV 109 /XHeight 443 /StemH 43 /CharSet (/F/i/n/d/g/S/t/r/a/e/c/G/m/E/q/u/v/l/o/f/x/s/N/h/b/hyphen/P/period) /FontFile3 220 0 R >> endobj 211 0 obj << /Type /Font /Subtype /Type1 /FirstChar 45 /LastChar 120 /Widths [ 375 313 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 738 707 884 0 0 0 0 0 0 880 0 769 0 0 625 0 0 0 0 0 0 0 0 0 0 0 0 0 547 625 500 625 513 344 563 625 313 0 0 313 938 625 563 0 594 459 444 438 625 594 0 594 ] /Encoding /WinAnsiEncoding /BaseFont /LPCNOF+CMBX12 /FontDescriptor 210 0 R >> endobj 212 0 obj << /Length 1272 /Filter /FlateDecode >> stream ����PG�T�Y�P�@��/��b� �Y��G͍!\�Z��4�7 Ty��v0˝�>��$R��FD��cE�6$��zq��e)�_�} I tried to find out how to convert this to strategic or normal form (which is the task I am supposed to do) but I am not completely sure on how I would do this considering that nature is present at a lower node. trailer << /Size 226 /Info 201 0 R /Root 204 0 R /Prev 110415 /ID[<7edc8a1c024a48857fb38cc4be3d8897><0446df877c3ffd6fe55b2658bcd8f0f8>] >> startxref 0 %%EOF 204 0 obj << /Type /Catalog /Pages 195 0 R /Metadata 202 0 R /PageLabels 193 0 R >> endobj 224 0 obj << /S 1363 /L 1488 /Filter /FlateDecode /Length 225 0 R >> stream 5��ozb�@n�J�Gw�� Jd�� 0000014325 00000 n ��?�)�K�f��t�2{Ԭp�,� RŔ Normal-form game is a game when players decide simultaneously, time is meaningless. • Another problem: there are exponentially many pure strategies, so normal form is exponentially larger –Even given polynomial-time algorithms for normal form, time would still be exponential in the size of the extensive form But how do we go about converting a Normal form game to Extensive Form. 0000003403 00000 n In this game, the rst mover is not a player but \Nature". ��$�\�Fx��㜰S�9��6 �> dO7h��4��l��6"; ��6�Z�+Q6H��AC-}��:�gYR��ސ�1d�Tj4�oXUߺ�K�]?í�.�W�Ûз��7=��.��/8;�~rYVtZ�*�"�8/OŠ�?��r�JM)��WՖVV�ɞ��M��Q�oT��Qי'�.u��{��l�GE�VR�K��\��S��i��=�u��[�D�d�_˓tV1P��о�4o��nJ_��V Woj5�Tl`��NK��a��x] {'mHЦ0|��:��C�٩D�*׉��b�A'�y��!�TU��/��0d\�}��dQQ\aH^��p�C#/�ďB��((r��$H�佀>��?Q�u(�PT�hT��.+�~�â@�[�P ��dϑkP�7C��_�XwC�e/�ʇ�?JO×��WoQw�~��7��Z��־m �9g�i��>�㔫ޔ��E��5bM�\]Hh The normal-form (or strategic-form) representation, in which the above informa-tion is summarized by use of strategies. The extensive-form representation, in which the above information is explicitly described using game trees and information sets; 2. ��-E�r�@k�%�frޘU��W>��gФ ... Extensive and strategic form in game with uncertainty. Z��MЁ��'�;��VLM5�ꨊb�2��I��-�$ �S��Ьϑ�A��W�奺 Extensive Form Games. ��TR5��7��屰��]�K�W%5)��-|�j5&>R��4vЦ�=�'��w��{��?35�p��}��y�=�ٙrsgڢR�{�|,��-`�%TY��[f� p\��푐��"[�P��\��+4^��/be ��S��bce��'�2�pyx��¼r1��aX��`X*��M��q��0��bq�Ö�`K��)�ab��9�+��E�� A game in extensive or strategic form is created and nicely displayed with a graphical user interface in a web browser. Game Theory: Lecture 12 Extensive Form Games Extensive Form Games We have studied strategic form games which are used to model one-shot games in which each player chooses his action once and for all simultaneously. In this lecture, we will study extensive form games which model multi-agent sequential decision making. Multiplayer game in extensive form. 0000000908 00000 n To avoid this, cancel and sign in to YouTube on your computer. I am confused by the rules how to converse extensive form game to the normal-form game. Switch camera. Let X a consist of all nodes x such that i(x)=a; A partition Pa of X a for each player a, i.e., P={I 1,I 2,..,I n} s.t. 0000013102 00000 n I�f�3� 0000004106 00000 n �)�\h�O-� • Therefore to ﬁnd the strategic game equivalent of an extensive form game we should follow these steps: 1. The first is, because there exist in normal form game, we can leverage results we have about the normal form, like the existence of equilibrium just by virtue of the fact that there's a corresponding game. normal form representation. Problem #3: Convert extensive-form to strategie-form, find Nash equilibria and subgame perfect Nash equilibria (12pts) Consider the following extensive-form game 1 Don't Veto Veto Y 2 2 1, 1 1, 1 2,0 0,2 2,0 In this game, Players 1 and 2 are deciding on a course of action, which may be X, Y, or Z. We incorporate uncertain exogenous events into the extensive form by introducing Nature as a nonstrategic player who acts randomly. © 2003-2021 Chegg Inc. All rights reserved. I With perfect information, a subgame perfect equilibrium is a sequential equilibrium. 5y�tJ�� L��n��Bd�Q|Ȏ��Q�"c�I�=Q/��q|��P2>��_72. | Extensive Form Games and Subgame Perfection ISCI 330 Lecture 12, Slide 6. Convert the extensive game into a strategic form game, by renaming the strategies in the extensive form as actions in the strategic form and making the payo s to a terminal history generated by a strategy pro le as the payo s to a action pro le. H��TLU�^��/�+�C��+��`bE;`��"f�M v3��2SV��&&J2M�҄DK�� XB,� �(2��S��K|w�1�?�/��{��? %PDF-1.3 %�� Videos you watch may be added to the TV's watch history and influence TV recommendations. In game theory, normal form or it is also called strategic form , is a description of a game. Player 2 is the one who actually makes the choice, but first, Player 1 may choose to veto Y, which is the option Player 1 prefers the least a) List all the strategies available to Player 1, and all the strategies available to Player 2 (Hint: Notice that Player 2 has two nodes...) b) Using your answer to a), create a game table to represent this extensive-form game in strategic form. Most cooperative games are presented in the characteristic function form, while the extensive and the normal forms are used to define non-cooperative games. H��{T��gXvg]ˀ��z�A!6 0000019072 00000 n Moreover, every extensive form game has a unique normal form representation.2 So knowing how to go from extensive to normal form is a very useful tool in analyzing games. 0000018617 00000 n The extensive form. Extensive form games contain the following: A game tree A list of players The names of players moving at each node A set of allowable actions at each node ��(be % 3��Q��0H�=g��|�� s5�-_\w�E�2�U�_#�-#�VR4�(�n�t�L5W1��͌ �I�J8�܏��aw��c��Z;)�|��f��dsgכ�M�ԅ�b��e ]T_��@��4T��4��Z�l? Recap Perfect-Information Extensive-Form Games Subgame Perfection Pure Strategies Example 5.1 Perfect-information extensive-form games 109 q q q q q q q q q q H H H H H H H H H H A A A A A A A A A A A A A A A 1 2 2 2 0 2 1 1 2 0 Privacy That is, a strategy is a complete plan for playing a game for a particular player. 0000014869 00000 n For all I, J in Pa, I … This is done with the help of Information Sets.. Information Sets. Hence, the usual procedure is to convert the extensive-form game to strategic form, and ﬁnd its equilibria. We learn how to construct the strategic-form of an extensive-form game when Nature takes a turn at bat. extensive form • Can just use normal-form representation –Misses issues of subgame perfection, etc. . 0000000811 00000 n This paper aims to make precise, in the context of epistemic models for games, some relations between the normal or strategic form representation of a game and the extensive or dynamic form representation. I Thm: Every nite extensive-form game with perfect recall has a sequential equilibrium. Extensive Form Game • In an extensive form game, a strategy for a player should specify what action the player will choose at each information set. . Convert the extensive game into a strategic form game, by renaming the strategies in the extensive form as actions in the strategic form and making the payoﬀs to a terminal history generated by a strategy proﬁle as the payoﬀs to a action proﬁle.. . n�ك��]� �{ֶ��\"��i�@�AV��܎go�ˑ�è�7�� W}"��'�&�R\��@է��u+�T��T�{�̃7E$EI��x6+&��L��S.ܜ�7e8��JFX�`V��D��]�T��D�A!_"��G�K��e�&��mH��X,�q��ٯ5�N��i��ǎ�E�8TZ�,��jtq��Kj�zTg��%�V��<7;�l~ȏ+��yS�K_��)-n%yّ%�4��Nz ��X��G�F&�(zэg��Q3�S�>��xJ&�@ ��Nlg��_�u�׆��e��G�;Y��L��_�w�^F7��y&x4w2$5��OK��y��L*�E��W� \s�a�_��_ �!��t�G)}�ʬq��;mJO��/W�u�h�6��J�W�D |抹 �pol��`�(Tc��#c��/��MlLJM�(X"P�M-M��5�4��p�� rU.��Zq��R3k�}�B��?��x�ˬr��$Zrâ�r�e��՟��y��96�l�$}��mk�0�۳��=GIyRWhG��fڹ�3A��Ȍ�__֭��ǀ��ɈC�1x~L�MrO�vm�c0��5� �*"٩F"R��Ǌt'��@u�5ʉ�U�,w��[$��3/%4²&|bF=�/��$$��Ec�� d*�.�p��=�x�_Hxq�P�H��ě�"��]��X��킶�n9��t�F�KΰpF�ˆS��#tg/Pu�ƽ�۴-tN�PH|��#i��T��$Pʒ��*��R� x��A�7��ko��x?\?$탣|��9;Y��V8��L�FCk�j�MKG��B��{�_m�K�3;�ʄLj��溣��n��3�MRB"w�,=~oB 'ȶăII�黙SSA¬��j�RWV_B�d��/��䭭C+#��F�z�vMpu� :p��A��Q�II��rF[��d�zx��@�� Extensive form can be converted to normal form, so previous results carry over But there are additional results that depend on the temporal structure In a perfect-information game, the extensive form is a game tree: Nonterminal node = place where an agent chooses an action Edge = … Cancel. Terms LFԁi-˳� �Eh�Q��X̄�Y_^BLŁHΑ�V�2��w��kQ@U�OM�R#%�Q� In the depicted matrix, if player 1 chooses strategy A and player 2 chooses strategy B, the set of payoffs given by the outcome would be p 1A,p 2B.If player 1 chooses strategy B and player 2 chooses strategy A, the set of payoffs would be p 1B,p 2A.. (See the right panel of Figure 1.) The strategic form of an extensive-form game Recall that when we studied strategic-form games we specified a game by a triple: (I,S,u), where I was the player set, S was the space of strategy profiles, and u was an n-tuple of player utility functions ... For, every finite extensive form game $\Gamma^E$, there exists a single strategic form representation $\Gamma^N =[I^N,\{S^N_i\},\{u^N_i(\cdot)\}]$ (up to … The strategic form allows us to quickly analyse each possible outcome of a game. . 2 The converse the statement, however, is not true: A normal form game will very likely have more than one extensive form representations. I am teaching myself game theory and I am just confused on how to convert extensive form to normal form when there are different stategies for player 2' depending on the player 1's stretegie. Every finite extensive form game is associated with a unique strategic form representation. This should not be surprising: after all, we obtained Another copy of the game tree is provided here for your benefit. Now extensive form games will be discussed. That is, at the beginning of the game, there is a random selection of whether Player 1 or Player 2 gets to move, each being chosen with … Every extensive-form game can be expressed as a strategic-form game. Confirm. A pure strategy assigns an action to every information set controlled by the player. ?�� @�Q ��M�ܗ=P'(��?d��}��R�Ct�)��e�;��2'��趀��`��$�R��ɇ�r��H��=�DF�J�M ��~F� Y�2 ��ϧ;�-΄�k��og��x��[�[��t��dZ��ˉ3TP��T�R>��T9��r:�r"��ҫtT��P�a">ʢM��i,6�ް��0�W��䕿��5��Q��G脺�6��ōQ��m��5�׈�Z׾|�'�vm��A ёaU��Q>��x��U�s�t(�\�Q�qf;LF�m��9��bӧ��+��XcӚ��n�EW��G��wPK�k��.��Z��}�X$� ,�=�i:L䪼��f2LQU��΅��j{X_�y��cs�G֙%*�qv2+��=Zo5�d�gn��G�-Sb��V�W�r�l�Ym��c��2O�z�ym��=��&�R�AgW�;�\�j�U�j�J\�F�)�e�a��?H^�hs�#�-�1=��ϳ��U27��$�,Z8��#�E��l�F*T �վ)�m�p��tT�!V�Ec�q��Gk�r�AV? : I i ⊂ X a. 0000005454 00000 n 0000018538 00000 n Extensive form game is a game tree when players make decision one by one, so the time matters, and players play sequentially. In a normal form representation of the sequential game you have to show every possible move available to every player, even the moves that do not exist. For the class of extensive form games considered here the pure strategy abstraction assumption results in 2×2 bimatrix strategic form games. View desktop site, Problem #3: Convert extensive-form to strategie-form, find Nash equilibria and subgame perfect Nash equilibria (12pts) Consider the following extensive-form game 1 Don't Veto Veto Y 2 2 1, 1 1, 1 2,0 0,2 2,0 In this game, Players 1 and 2 are deciding on a course of action, which may be X, Y, or Z. 2. ˊ˪F��f��~H"�Yۛ�� 52�OF��Wz�i� ~� The strategic form allows us to quickly analyse each possible outcome of a game. extensive form representation of a social situation into the strategic form. Obviously the Same - if unique strategic form from single extensive form Not so Sure - if we get the same strategic for from two different extensive form games Kohlberg & Mertens - based on 50s literature; published in Econometrica; looked at transformations in extensive form that are … I A sequential equilibrium is a Nash equilibrium. 0000002066 00000 n There are at least three basic forms of strategy in the business world and it helps to keep them straight.