London Judgment & Decision Making Group
Spring term 2014 – 2015
Organizers
Neil Bramley
University College London
Contact details:
Department of Experimental Psychology
Room 201, 26 Bedford Way, London, WC1H 0AP
UK
Telephone: +44 (0) 79 1441 9386
E-mail: neil.bramley.10@ucl.ac.uk
Leonardo Weiss-Cohen
University College London
Contact details:
Department of Experimental Psychology
Room 200, 26 Bedford Way, London, WC1H 0AP
UK
Telephone: +44 (0) 20 7679 7570
E-mail: l.cohen.12@ucl.ac.uk
Eric Schulz
University College London
Contact details:
Department of Experimental Psychology
Room 204c, 26 Bedford Way, London, WC1H 0AP
UK
Telephone: +44 (0) 20 7679 7570
E-mail: eric.schulz.13@ucl.ac.uk
LJDM website
http://www.ljdm.info
LJDM members’ (Risk & Decision) list
Contact: Dr Marianne Promberger (marianne.promberger@kcl.ac.uk)
Seminar Schedule
January - March 2015
Wednesdays, 5:00 pm in Room 313, 26 Bedford Way, UCL Psychology
14th January
Effort and values in decision making
Magda Osman
Queen Mary, University of London
21st January
Choice proliferation increases risk-taking and reduces choice deferral
Thomas Hills
University of Warwick
28th January
Do humans make good decisions?
Chris Summerfield
University of Oxford
4th February
Separable processes in the generation of random sequences: Data and a model
Rick Cooper
Birkbeck, University of London
11th February
TBC (Modelling confidence and social interaction from a decision-theoretic
perspective)
Dan Bang
University of Oxford
18th February
READING WEEK (NO SEMINAR)
25th February
The joint effect of the classic choice phenomena and the role of experience
Ido Erev
Technion and University of Warwick
4th March
How do risk attitudes affect measured confidence?
Chris Starmer
University of Nottingham
11th March
TBC (The automatic statistician)
James Lloyd
University of Cambridge
18th March
TBC
Nathan Ashby
Carnegie Mellon
25th March
Memory biases in risky decisions from experience
Elliot Ludvig
University of Warwick
Abstracts
14.01.15
Effort and values in decision-making
Magda Osman
Queen Mary, University of London
Do we make the same decisions when faced with mentally effortful contexts as the ones we make
in physically effortful contexts? Several value-based decision making theories make broadly
similar assumptions that there should not be any fundamental differences between decisions in
these two contexts. However, there is remarkably little work directly comparing mental-effortbased decision-making with physical-effort-based decision-making. The present set of
experiments address this gap in the literature, and show that 1) the relationship between values
and effort-based decision making is by no means straightforward, and 2) that mental and physical
effort based decisions differ.
21.01.2015
Choice proliferation increases risk-taking and reduces choice deferral
Thomas Hills
University of Warwick
Choices can be risky. Unfortunately, more choices can be riskier. We present research showing
that in choices between monetary gambles, choice enriched environments increase risk taking and
lead to less choice deferral. Specifically, we compared decisions from experience with decisions
from description. In decisions from experience, when people sample a gamble they experience
individual outcomes; people must repeatedly sample gambles to learn about the gamble's
outcomes and probabilities. In decisions from description, information about the probabilities and
outcomes are provided at the same time and repeated sampling is unnecessary. A typical finding
is that people underweight rare events in decisions from experience and overweight rare events in
decisions from description: a phenomenon called the description-experience gap. To investigate
the influence of set size on choice, we increased the number of alternatives (to more than 30
options) in two standard choice paradigms: The sampling-paradigm (decision from experience),
where people can sample freely over alternatives before making a final decision, and the decision
from description paradigm, where people can deliberate over complete information about
outcomes and probabilities at the same time before choosing. In the first experiment, gambles
were either very risky or fairly safe and payoffs were sampled from similar distributions.
Increasing set size increased the sample size in both conditions, but led to fewer samples per
gamble. In the sampling paradigm this increased the likelihood of experiencing rare, risky events.
When choice was over gains, this led to increased choice for riskier options; people tended to
choose options associated with large (rare) gains. Over losses, set size had no influence on risky
choice; encountering rare events led participants to favor other risky gambles where rare events
were not encountered, as they do for small set sizes. Importantly, the observation that decisions
from experience leads to underweighting of rare events was reversed for large set sizes in the
gains domain; instead, people chose as if they overweighted rare events. In a second experiment,
we gave participants £1 for showing up and then offered them the opportunity to buy gambles
with positive payoffs. We added a button to allow participants to, after free sampling of
alternatives, either keep their money (defer choice) or to choose one of the alternatives. In both
decisions from description and decisions from experience choice deferral went down as set sizes
increased. Moreover, in both experiments, choices were not chosen at random but were predicted
by what the participants saw when they sampled alternatives. Overall, our results indicate that
context effects associated with increasing set sizes are not always readily apparent from twoalternative decisions. However, the increase in risky choice associated with experienced gains is
predicted from standard choice models. These effects also extend to questions of choice deferral
and information overload, for which we found no evidence of either.
28.01.2015
Do humans make good decisions?
Chris Summerfield
University of Oxford
Human performance on perceptual classification tasks approaches that of an ideal observer, but
economic decisions are often inconsistent and intransitive, with preferences reversing according to
the local context. I will discuss the view that suboptimal choices may result from the efficient
coding of decision-relevant information, a strategy that allows expected inputs to be processed
with higher gain than unexpected inputs. Efficient coding leads to 'robust' decisions that depart
from optimality but maximise the information transmitted by a limited-capacity system in a
rapidly-changing world. I will consider recent work from my lab and elsewhere showing that
when perceptual environments are variable or volatile, perceptual decisions exhibit the same
suboptimal context-dependence as economic choices, and we propose a general computational
framework that accounts for findings across the two domains.
04.02.2015
Separable processes in the generation of random sequences: Data and a model
Rick Cooper
Birkbeck, University of London
When participants are required to generate “random” sequences of responses their behaviour
typically betrays a number of well-known biases, such as the avoidance of immediate repeats and
a tendency to produce stereotyped sub-sequences. These have been accounted for within verbal
models in which executive processes modulate schema-based behaviour. In this talk I will first
present data from a dual-task study which fractionates the involvement of at least two executive
processes in random generation. Following this, I will demonstrate how participant behaviour
within the dual-task study can be captured by a general computational model of the interaction of
executive sub-processes.
11.02.2015
TBC (Modelling confidence and social interaction from a decision-theoretic perspective)
Dan Bang
University of Oxford
TBC
25.02.2015
The joint effect of the classic choice phenomena and the role of experience
Ido Erev
Technion and University of Warwick
TBC
04.03.2015
How do risk attitudes affect measured confidence?
Chris Starmer
University of Nottingham
We examine confidence in own absolute performance using two elicitation procedures: selfreported (non-incentivised) confidence and an incentivised procedure that elicits the certainty
equivalent of a bet based on performance. The former procedure reproduces the “hard-easy effect”
(overconfidence in easy tasks and underconfidence in hard tasks) found in a large number of
studies
using
non-incentivised
self-reports.
The
latter
procedure
produces
general
underconfidence, which is somewhat reduced when we filter out the effects of risk attitudes.
However, even after controlling for risk attitudes our incentivised procedure leads to significant
underconfidence, and does not lead to better calibration between confidence and performance than
non-incentivised self-reports. Finally, we find that self-reported confidence correlates significantly
with features of individual risk attitudes including parameters of individual probability weighting.
11.03.2015
TBC (The Automatic Statistician)
James Lloyd
University of Cambridge
TBC
18.03.2015
TBC
Nathan Ashby
Carnegie Mellon
TBC
24.03.2015
Memory biases in risky decisions from experience
Elliot Ludvig
University of Warwick
TBC