The Effect of Learning and Fatigue on Preferences and WTP in a ...

they all are larger than one, <strong>and</strong> hence the error variance is smaller than one, suggestive <strong>of</strong> the
already established learning effect. What is also important to note is that it appears, from the bottom
row <strong>of</strong> the table, that the learning effect only takes place primarily in the first CS, <strong>and</strong> not as much
successively through the following CS as can be seen from the insignificant differences between the
scale factors. This is in contrast to the findings by Bateman et al. (2008b), where the most reliable
estimates are found during the first 4 <strong>and</strong> last 4 CS, whereas the middle 8 CS somewhat surprisingly
are the least reliable estimates. <strong>The</strong> results are however largely in accordance with Ladenburg &
Olsen (2008) who find evidence that preferences become stable after the first three CS, supporting
the notion <strong>of</strong> learning effects taking place.
6. Conclusion
This paper addresses the issues <strong>of</strong> how learning <strong>and</strong> fatigue effects related to the repeated choices
potentially affect respondents’ stated preferences in a Choice Experiment setting. <strong>The</strong> main focus is
on changes in preference structure, error variance <strong>and</strong> willingness-to-pay. To the best <strong>of</strong> the
authors’ knowledge this paper is the first to provide an internal test across all these three measures
in one study. In a case study concerning food quality attributes in chicken breast filet, the results
show that a learning effect is indeed present in a sequence <strong>of</strong> 16 choice sets, whereas there is no
evidence <strong>of</strong> fatigue effects. This conclusion is based on an observed reduction in the error variance
for the last 8 choice sets relative to the first 8 choice sets – a result implying that preferences have
become relatively more stable in the last half <strong>of</strong> the choice set sequence which is in accordance with
the Discovered Preference Hypothesis <strong>and</strong> the concept <strong>of</strong> learning. An analysis incorporating choice
set specific scale factors reveals that the main part <strong>of</strong> the observed learning process takes place in
the first choice set. <strong>The</strong> overall preference structure is found to differ significantly between the two
sequences <strong>of</strong> choice sets. This suggests that the learning effect leads to changes in overall
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