sesgo de proporcion

8/12/2019 Sesgo de Proporcion

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Psicologa del Pensamiento

Prctica sobre:

EL SESGO DE PROPORCIN

Material complementario:

Fernnde!"errocal# P$ % Se&'ra# S$ ()**+,$ El ses&o de porporci-n$ En P$

Fernnde!"errocal % C$ Santamar.a (Eds$,# Manual prctico de

psicologa del pensamiento$ (P&s$ +)/!+0/,$ "arcelona: 1riel$


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EL SESGO DE PROPORCIN

Diego Alonso (Universidad de Almera)

yPablo Fernndez Berrocal(Universidad de Mlaa)

23ere are di44erent 5a%s o4 e6pressin& t3e probabilit% o4 an e7ent$ One o4

t3em consists o4 t3e 'se o4 ratios$ 23's# one can sa% 4or e6ample# t3at t3e

probabilit% o4 8 3appenin& is 9+ in )*9$ 23is can &i7e place to a ratio bein&

e6pressed b% means o4 di44erent n'mbers: 9+ in +*9# +* in +**9# etc$ In spite o4

t3e mat3ematical e'i7alence o4 t3e t5o pre7io's ratios# a s'rprisin&

p3enomenon 3as been obser7ed 53en ;'d&in& t3e probabilit% o4 a lo5

probabilit% e7ent: man% people ;'d&e it as less probable 53en it is e6pressed as

a ratio o4 small n'mbers (e$ &$# + in )*, t3an o4 lar&e n'mbers (e$ &$# +* in )**,$

23is p3enomenon is


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5innin& t3an ba& 1 (4or e6ample# A in +** 7s$ + in +*B Denes!Ra; ? Epstein#

+@@,$ In t3is st'd% o4 Denes!Ra; and Epstein# almost 3al4 o4 t3e participants

pre4erred t3e option 9A in +**9 to t3e option 9+ in +*9$ Still


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t5o in4ormation!processin& s%stems$ In most sit'ations# t3e t5o s%stems

operate s%nc3rono'sl%# people bein& onl% a5are o4 53at seems to be a sin&le

process# and in ot3er circ'mstances t3eir di44erences come to li&3t# as 3appens

in t3e R" paradi&m$

1ccordin& to CES2# t3e R" e44ect 5o'ld be attrib'ted to t5o 4acets o4 t3e

concrete processin& t3at carries o't t3e e6periential s%stem (Pacini and

Epstein# +@@@b,: t3e n'merosit% e44ect and t3e small!n'mbers e44ect$ In

accordance 5it3 t3e 4irst 4acet# t3e e6periential s%stem codes and 'nderstands

better 53ole n'mbers t3at ratios# beca'se n'mbers are more concrete t3an

relations bet5een n'mbers# 53ic3 is co3erent 5it3 ot3er 4indin&s s3o5in& t3at

t3e sensibilit% to 4re'encies !n'mbers ! is one o4 t3e more important co&niti7e

operations (Gallistel# +@@*B Gear%# +@@/B Staddon# +@AA,$ People code

a'tomaticall% t3e in4ormation abo't 4re'encies# pre7ailin& o7er ot3er more

rational considerations# s'c3 as ratios# 53ic3 can constit'te an important so'rce

o4 errors in probabilistic ;'d&ements (Pel3am# S'marta# and M%a


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a&ainst a &ro'nd o4 man% more 53ite balls# and (0, t3e a't3ors ass'me t3e

a44irmati7e representation principle# accordin& to 53ic3 t3e e6periential s%stem

can code t3e positi7e representations (in t3is case# 9to e6tract a red ball9, more

easil% t3an t3e ne&ati7e representations (t3at is to sa%# 9not to e6tract a 53ite

ball9,# beca'se t3e a44irmation is more concrete t3an t3e ne&ation$

23e second 4acet# t3e small!n'mbers e44ect# consists in t3at# at t3e

e6periential le7el# small n'mbers are easier to 'nderstand t3an lar&e n'mbers

beca'se t3e% are more concrete (easier to 7is'alieB Pai7io# +@A,$ 23en# 53en

t5o e'i7alent lo5 probabilit% ratios are presented# one e6pressed 5it3 small

n'mbers and t3e ot3er 5it3 lar&e n'mbers# people 5ill 'nderstand better (at t3e

e6periential le7el, t3at t3e e7ent 3as a 7er% lo5 probabilit% o4 3appenin& 53en

t3e ratio is e6pressed 5it3 smaller n'mbers (Pacini and Epstein# +@@@aB

Gallistel# +@@*B Sie&ler# +@A+B S'rber ? aines# +@AH,$ 23at is to sa%# 4or

e6ample# t3e ratio +)* is more 'nderstandable and t3ere4ore more con7incin&

t3at it represents an e7ent o4 7er% lo5 probabilit% t3an t3e ratio +*)**# 53ic3

5ill ca'se t3at t3e s'b;ecti7e probabilit% in t3e 4irst case to be smaller t3an in

t3e second one$

1ccordin& to t3e e6planation pro7ided b% CES2# t3ese t5o 4acets o4 t3e

concrete t3in


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ratio @*+**# t3e small!n'mbers e44ect 5o'ld ind'ce 's to c3oose @+* since

t3ese small n'mbers 5o'ld e6press more clearl% (4rom t3e e6periential s%stem,

t3e idea o4 a 3i&3 probabilit% 4or t3eir occ'rrence (Pacini and Epstein# +@@@b,$

>ir


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1C2IID1D PRC2IC1

2' tarea 7a a consistir en comprobar el ses&o de proporci-n con otros

contenidos$ Para ello debes de pasar# de 4orma indi7id'al# a )* personas elsi&'iente c'estionario (7er 3o;a ad;'nta, en el 'e se describe 'na 3ipotticasit'aci-n de elecci-n$

Debes de leerle a cada participante el te6to completo % comprobar 'ese 3a comprendido$

na 7e terminada la reco&ida de datos (de los )* participantes,# debesanaliarlos estad.sticamente ('tiliando el estad.stico C3i!c'adrado, %4inalmente elaborar 'n in4orme en el 'e se e6pon&a con claridad % precisi-n('tiliando el 4ormato con7encional de presentaci-n de res'ltados

e6perimentales, el est'dio realiado$

Esta prctica p'ede 3acerse indi7id'almente o en &r'po (0 al'mnosascomo m6imo,


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Ima&.nate 'e tienes delante de ti dos ca;as 'e contienen dos

tipos de 4i&'ras: coraones % trboles$

La ca;a pe'ea contiene +* 4i&'ras: @ coraones % + trbol(+* son trboles, La ca;a &rande contiene +** 4i&'ras: @* coraones % +*

trboles (+* son trboles,

Debes co&er# sin mirar# 'na 4i&'ra de 'na de las ca;as$ La ca;a'e tQ pre4ieras$ Si co&es 'n trbol &anas +** e'ros$

Lo interesante de esta sit'aci-n es 'e# a pesar de 'e la

probabilidad de &anar es la misma en las dos ca;as# al&'naspersonas pre4ieren 'na ca;a a otra$

Por 4a7or# contesta a las si&'ientes pre&'ntas (selalas con 'na8,:

+,' ca;a ele&ir.as tQ=

TTT la ca;a pe'ea

TTT la ca;a &rande

),' ca;a crees 'e eli&en la ma%or.a de las personas=

TTT la ca;a pe'ea

TTT la ca;a &rande

0,' ca;a crees 'e ele&ir.a 'na persona totalmente l-&ica=

TTT la ca;a pe'ea

TTT la ca;a &rande

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