International Choice Modelling Conference, International Choice Modelling Conference 2015

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Measuring Attribute Non-Attendance in Stated Choice Experiments using statements, inference and eye-tracking – Does presentation format matter?
Søren Bøye Olsen, Kennet Uggeldahl, Catrine Jacobsen, Thomas Hedemark Lundhede

Last modified: 11 May 2015

Abstract


While many different decision processing strategies have been identified in the Stated Choice Experiment (SCE) literature (see for example Hensher (2010) for an overview), one that has received significant attention is attribute non-attendance, i.e. when respondents ignore one or more attributes of the alternatives when making their choices. Attribute non-attendance has been measured in different ways. An often used approach in practice is to simply ask respondents a follow-up question regarding which attributes they ignored, if any. This is referred to as stated non-attendance (SNA), and the obtained information can subsequently be taken into account in modelling by adjusting the likelihood function accordingly. A somewhat more sophisticated approach is instead to infer non-attendance from econometric models based on observed choices. This is referred to as inferred non-attendance (INA). Despite aiming at the same thing, several comparisons have found that the SNA and INA approach do not reach the same conclusions (Scarpa et al. 2013), and it seems like the majority of papers dealing with non-attendance have taken the view that INA is superior to SNA since respondents might make mistakes when answering the non-attendance statements. However, as highlighted by Alemu et al. (2013), this could be explained by the fact that the typical way of asking the non-attendance follow-up question in the SNA approach is actually ambiguous in the sense that respondents may interpret the question in a different way than the analyst. Furthermore, the SNA approach is prone to strategic answering. The INA approach is not flawless either. As well as any other model attempting to infer behavior from choices, the INA approach rests on a number of modeling assumptions that are subject to uncertainty and the statistical power of the available data.

Against this backdrop, a new non-attendance approach has recently emerged – one that would appear to overcome some of the problems with SNA and INA by providing an exogenous and objective measure of non-attendance. As eye-tracking technology has improved markedly in recent years and has now become affordable to most researchers, a new path of investigating response behavior and attribute processing in SCE has emerged. Scarpa et al. (2013) suggests that this should also prove useful in relation to non-attendance. So far, only two papers (Balcombe et al. 2014, van Loo et al. 2014) have utilized this by measuring the so-called visual non-attendance (VNA) which may be defined as visually ignoring information about attribute levels. We continue this line of investigation by conducting an empirical CE using eye-tracking technology. Specifically, we compare the SNA, INA and VNA approaches, hypothesizing that the VNA will prove to be the more reliable measure since it is beyond the control of the respondent, and no modelling assumptions are needed. Furthermore, we test for impacts of presentation format, hypothesizing that picture presentations of alternatives will lead to less non-attendance than table presentations of the same alternatives. If so, this also allows investigating whether there are differences in the differences across the three non-attendance approaches.

In one of the biggest eye-tracking SCE studies so far, a total of 193 respondents answered a food choice experiment about minced meat packages varying in environmental and ethical labelling. Respondents were placed in front of a screen with an eye-tracking device which recorded their eye movements during the process. The eye-tracker sampled the respondent’s eyes 60 times a second, measuring e.g. gaze location. By defining areas of interest based on the on-screen location of each attribute in the choice tasks, we are able to objectively assess whether or not each respondent has (visually) paid attention to all attributes in all choice sets. We will present and compare models and WTP estimates where a) SNA is incorporated through dummies adjusting the likelihood contributions, b) INA is assessed using the coefficients of variation approach as well as the latent class approach, and c) VNA is incorporated through dummies adjusting the likelihood contributions. We will do this for two split samples: One half of the respondents were presented with photos of the alternatives while the other half of the sample only saw table representations of the alternatives. Besides testing for differences in non-attendance, the split samples will be tested for differences in a range of descriptive statistics (focusing particularly on eye-tracking related measures) as well as for differences in error variance. The data has been collected but the final analysis has yet to be done.

 

References:

Alemu, M. H., M. R. Mørkbak, S. B. Olsen, and C. L. Jensen. (2013). Attending to the reasons for attribute non-attendance in Choice Experiments. Environmental and Resource Economics 54(3):333-359

Balcombe, K., Fraser, I. and McSorley, E. (2014) Visual attention and attribute attendance in multi-attribute choice experiments. Journal of Applied Econometrics. ISSN 1099-1255 (In Press)

Campbell D, Hutchinson WG, Scarpa R (2008) Incorporating discontinuous preferences in to the analysis of discrete choice experiments. Environ Resource Econ 41(3):401–417

Hensher DA (2010) Attribute Processing, Heuristics and Preference Construction in Choice Analysis. (Invitational Keynote Paper for Choice Modelling Conference, Leeds UK, March 30-April 1 2009). In Hess S, Daly A (eds.) State-of Art and State-of Practice in Choice Modelling, Emerald Press, UK,pp.35-70.

Scarpa, R., R. Zanoli, V. Bruschi, and S. Naspetti. (2013). Inferred and stated attribute non-attendance in food choice experiments. American Journal of Agricultural Economics, 95(1): 165-180.

van Loo, E. J., Nayga Jr, R. M., Seo, H. S., & Verbeke, W. (2014). Visual Attribute Non-Attendance in a Food Choice Experiment: Results From an Eye-tracking Study. Selected Paper prepared for presentation at the 2014 AAEA Annual Meeting, Minneapolis, July 27-29, 2014.

 

 


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