Metodi sperimentali applicati alla domanda di trasporto

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Metodi sperimentali
applicati alla domanda di trasporto  

•  
• Alessandro Innocenti
• Università di Siena
• in collaborazione con
• Patrizia Lattarulo (IRPET) e Maria Grazia
  Pazienza (Università di Firenze)
• Seminario interno IRPET Toscana
• Firenze 26 ottobre 2011

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The view of a cognitive economist

• Many experimental economists seem to view their
  enterprise as akin to silicon chip production.
  Subjects are removed from all familiar contextual
  cues. Like the characters 'thing one' and 'thing
  two' in Dr. Suess' Cat in the Hat, buyers and
  sellers become 'persons A and B', and all other
  information that might make the situation
  familiar and provide a clue about how to behave
  is removed.
• George Loewenstein (1999)

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The context free experiment

• The context-free experiment is an elusive goal
  and
• not necessarily a good thing
• Games in the laboratory are usually played
  without labels but subjects inevitably apply
  their own labels
• A major discovery of cognitive psychology is how
  all forms of thinking and problem solving are
  context-dependent (language comprehension)
• The laboratory is not a socially neutral context,
  but is itself an institution with its own formal
  or informal, explicit or tacit, rules

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The context free experiment
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Label matters - Wasons test

• Jones-Sudgen (2001)
• Wasons selection task to test positive bias
  confirmation tendency, when testing an existing
  belief, to search for evidence which could
  confirm that belief, rather than for evidence
  which could disconfirm it
•  
• Correct response is facilitated by adding
  thematic content to the task, i.e. by providing
  a cover story which accounts for the statement
  and gives some point to the selection task
  subjects become more rational and not less
  rational

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Travel mode choice

• Aim to extend previous experimental evidence on
  travel mode choice by providing subject not only
  with information acquired through personal
  experience, but also with actual travel times of
  the alternative non chosen travel modes
• Key Findings
• subjects show a marked preference for cars
• are inclined to confirm their first choices
• exhibit a low propensity to change travel mode

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Background literature

• Experimental literature on travel mode choice
  relies widely on studies on route choice
• Common object coordination games, i.e. the
  payoff each traveler can achieve is conditional
  on her/his ability to diverge from or to converge
  with other travelers choices
• Selten et al. (2007), Ziegelmeyer et al. (2008),
  Razzolini-Dutta (2009) provide laboratory
  evidence that choices between route A and route B
  generate Nash equilibria

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Background literature

• Evidence from the field shows that these learning
  processes are affected by cognitive biases
  (Kareev et al. 1997, VerplankenAarts 1999)
• To provide travelers with more accurate
  information on actual travel times does not
  necessarily increase their propensity to minimize
  travel costs (Avineri-Prashker 2006)
• Information is better processed when travelers
  lack long-term experience on travel time
  distribution (Ben EliaErev-Shiftan 2008)

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Background literature

• Cars are generally perceived as travel means
  giving people the sensation of freedom and
  independence
• The costs associated to car use are undervalued
  because they not paid contextually with car use
• Pollution or social costs due to car accidents
  are often neglected and not easily computable
• These factors explain the presence of a general
  propensity to use private cars and of a
  psychological resistance to reduce it
• Van Vugt et al. 1995, Tertoolen et al. 1998,
  Bamberg et al. 2003

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The design

• 62 undergraduate students (31 women and 31 men)
  from the University of Firenze
• Computerized experiment
• Between subject
• Each session lasted approximately an hour
• Average earnings 18.4 euro

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The design

• 1) Choice between car or metro
• Metro travel costs are fixed, while car costs
  are uncertain and determined by the joint effect
  of casual events and traffic congestion
• 2) Choice between car or bus
• Car and bus are both uncertain and determined by
  the combination of casual events and traffic
  congestion.
• Travelers utility only depends on travel times,
  which are converted in monetary costs. After each
  choice, subjects are informed of actual times of
  both available modes, but not of the probability
  distributions determining casual events

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The design
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The design

• Metro Car treatment- the expected total costs of
  car and metro were equivalent if the share of car
  users was not greater than 55
• Bus 1.0 Car treatment - the expected total costs
  of car and bus were equivalent if the share of
  car users was not greater than 55
• Bus 0.8 Car treatment- the expected total cost of
  the bus was 20 lower than car expected total
  costs if the share of car users was not greater
  than 55.

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Results Preference for Cars

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Results Preference for cars

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Results Preference for cars

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Results Preference for cars

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Results Preference for cars

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Results First Choice Effect

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Results First Choice Effect

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Results Travel Mode Stickiness

• The first choice effect decreases the propensity
  to change travel mode
• Only 28.6 of the subjects in the metro treatment
  and 39 of the subjects in the bus treatments
  change more than 20 times over 50 periods.
• On average, subjects change mode 17.7 times in
  the metro treatment and 18.0 times in the bus
  treatments

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Conclusions

• Travel mode choice is significantly affected by
  heuristics and biases that lead to robust
  deviations from rational behaviour
• Travelers choose modes using behavioural rules
  that do not necessarily involve the minimization
  of total travel costs.
• Subjects show a marked preference for cars, are
  inclined to confirm their first choice and
  exhibit a low propensity to change travel mode.

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Conclusions

• In repeated travel mode choice, available
  information is not properly processed, cognitive
  efforts are generally low and rational
  calculation play a limited role
• The habit of using cars should be assumed to be
  relatively resistant, to the effect of economic
  incentives
• Little progress can be expected by asking
  travelers to voluntarily reduce the use of a car
  or even by subsidizing public transport costs

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Back to Methodology

• One of the basic tenets of laboratory methodology
  is that the use of non-professional subjects and
  monetary incentives allows making subjects
  innate characteristics largely irrelevant
• In our experiment, it is as if subjects take into
  the lab the preferences applied to real choices
  and stick to them with high probability
• This inclination to prefer cars tends to override
  the incentives effect
• Labels give subjects clues to become less and not
  more rational

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Internal vs. External Validity

• Internal validity - ability to draw confident
  causal conclusions from one's research
• External validity - ability to generalise from
  the research context to the settings that the
  research is intended to approximate
• Experiments have the reputation of being high in
  internal validity but low in external validity
• Field studies of being low in internal validity
  but high in external validity

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The power of labels

• In our experiment, subjects behavior depends
  more on prior learning outside the laboratory
  than on expected gains in the laboratory
• Labels have the power to increase external
  validity with a minimal sacrifice of the internal
  validity
• To test learning and cognitive models, it is
  necessary to remind and to evoke contexts which
  may activate emotions, association, similarities
  in the laboratory

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Some examples

• Tram
• http//www.youtube.com/watch?vH1XrL_U38-c
• Metro
• http//www.youtube.com/watch?vdYmsmWqCV0A
• Car
• http//www.youtube.com/watch?NR1vSk-WlKTtExA
• Progetto ALBO
• http//www.progettoalbo.it/images/video/trailer.mp
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