ワークショップ
2008年度 第2回 意思決定班ワークショップ
- 日時
- 2008年8月18日(金) 14:15-16:00
- 場所
- 早稲田大学戸山校舎 第3会議室(34号館2階)
- 参加人数
- 17人
- 報告概要
Petko Kusev (City University London)
Memory-biased preferences: The influence of accessibility on risky decision-making and judgments
Abstract:
We studied precautionary decisions where participants decided
whether or not to adopt a specified precaution with a known cost
in the face of a described risk. We compared the risks taken for
precautionary decisions with those taken for equivalent monetary
gambles. Applying Tversky and Kahneman's (1992) prospect theory
to these data we find that the weighting function required to
model precautionary decisions exhibit different properties than
those required to model choices between monetary gambles. This
result indicates a failure of the descriptive invariance axiom
of expected utility theory. For risky prospects with moderate
and high probabilities overweighting of probability is observed
- a finding not anticipated by prospect theory. We hypothesize
that precautionary decisions differ from monetary gambles
because the former cue accessible features in memory.
Accordingly, we report evidence that the accessibility of risky
prospects influences participants' preferences and decision
weights. Our results highlight a need for theories which
differentiate between decisions about monetary gambles and other
types of decision-making under risk and uncertainty. For
judgments, the experiments show that judged frequencies of
sequentially encountered stimuli are affected by certain
properties of the sequence configuration. We find (a) a
first-run effect whereby people overestimate the frequency of a
given category when that category is the first repeated category
to occur in the sequence and (b) a dissociation between
judgments and recall; respondents may judge one event more
likely than the other and yet recall more instances of the
latter. Judged frequency of categories of items is influenced by
the first run - which may reflect the operation of a judgment
heuristic. The distribution of recalled individual items does
not correspond to the frequency estimates, indicating that
participants do not make frequency judgments by sampling their
memory for individual items. We propose a simple strategy
whereby respondents use the first run as a cue to frequency that
accounts for this observation and other context effects on
memory and judgment.--
- 報告風景