March Social Decision Scheme Davis a theory of social decision scheme n AA An pp pn pppn r AA An PP Pn d d dn d d dn PPPn πππm dm dmdmn r πi rrrn pr p r pn rn r AA An rr rn rr rnr nr r m nr m r nr m pp pn r m i πi pp pnr m n m AA An D D D m n Davis social decision scheme SDS SDS π π πm PP Pn Davis Pp.Pp. SDS SDSsocial decision scheme

SDS rn rn D D D D D A A A A A A A A A A A A DLorgeSolomon AA DProportionality Aj Aj DEquiprobability DMajority, equiprobability otherwise DMajority if Aproportionality otherwise A vs. vs. vs. vs. vs. majority plurality proportionality equiprobabilitylorgesolomon LorgeSolomon majority plurality proportionality

March ABCD A B C D A B C D pppp Pi p p p P P majority plurality LorgeSolomon p

p A A A A B B B B p χ P P A A A A P B B B B P p P P Majority Plurality Proportionality Equiprobability LorgeSolomon P P Majority Plurality Proportionality Equiprobability LorgeSolomon P p p A Lorge Solomon LorgeSolomon

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Majority Plurality Proportionality Equiprobability LorgeSolomon LorgeSolomon A LorgeSolomon r LorgeSolomon t LorgeSolomon LorgeSolomon LorgeSolomon

SDS SDS LorgeSolomon LorgeSolomon p p p p p March

LorgeSolomon majority equiprobability pi A A B ABC A B C A B C AB A B B A A B B A SD SD A B p

March A B t A B p A A A B B B p P Majority Proportionality Equiprobability LorgeSolomon P

P Majority Proportionality Equiprobability LorgeSolomon P P P A LorgeSolomon majority B majority majority, proportionality, equiprobability ad hoc A LorgeSolomon B A B Majority Proportionality Equiprobability LorgeSolomon

March B A t LorgeSolomon SDS LorgeSolomon SDS A B

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March LorgeSolomon LorgeSolomon Lorge Solomon LorgeSolomon Davis, J. H. social decision scheme Davis SDS Pp. Pp. Davis, J.H.1973Group discussion and social interaction: A theory of social decision schemes. Psychological Review,,. Pp. Pp.

Experimental Studies on Group Decision-Making in terms of Davis SDS Theory ABSTRACT Two experiments were conducted in terms of J.H.Davis SDS (social decision scheme) theory. Experiment I dealt with the effects of task type (true-or-false type vs. preferance type) and group size3-person vs. 8-person groups) upon the decision schemes (majority, plurality, proportionality, equiprobability, or LorgeSolomon=truth-win) adopted by the groups. Subjects were recruited from junior high school352 pupils in total) and assigned to sex-homogeneous groups. Results showed: (1) 8-person groups working on a true-or-false task deliberated according to a LorgeSolomon scheme, while 3-person groups tended to adopt a majority scheme, and (2) groups of both sizes with a preferance type task adopted a scheme which was an indiscernible mixture of majority, proportionality and equiprobability, but when they were asked in post-experiment questionnaires, 3-person groups answered that their decision scheme had been closer to equiprobable whereas 8- person groups were closer to majority. Experiment with 22 3-person sex-homogeneous groups of college students studied the effect of time pressure on group decision-making. Results showed: (3) groups with a task of true-or-false type adopted a LorgeSolomon scheme when they could afford plenty of time for work, but they resorted to a majority scheme under time pressure and (4) groups with a task of preferance type made their decisions with a majority scheme when enough time was given, but under time pressure they shifted to a conflict-avoiding scheme of decision-making, a term which we coined to explain our particular result. Key Words: group decision-making, social decision scheme, group size, type of task, time pressure