Relevance Rule in Adding Up Non-Given Attributes in Travel Stated Choices: A Consideration Under Anchoring Perspective

This study is among the first studies investigating how non-given attributes are used in deciding stated choices for daily travel under anchoring perspective. Our theoretical work leads us to a conceptual model that non-given attributes are systematically included in the choice making process based on their relevance to the choice decision. The relevant rule for re-packing of the attribute set is activated in a way that the involvement of non-given attributes does not eliminate the influence of given attributes on choices. Notably, more non-given attributes are involved in choice decision when respondents deal with cases that are more difficult to trade-off between given attributes. To obtain empirical supports, a paper-based questionnaire interview was conducted. Findings based on 649 individual responses of travellers in Can Tho city, Vietnam successfully showed that travel time and travel cost significantly influence the stated choice between bus and motorcycle regardless of the involvement of respondents’ travel experiences. In addition, it was observed that all the investigated travel experiences were associated with stated choices in more difficult cases (more efforts to trade-off between travel time and travel cost) while fewer travel experiences were associated with stated choices in less difficult cases (less efforts to trade-off between travel time and travel cost). The positive association between the judgement difficulty based on given attributes and the number of anchors associated with stated choices suggests that the search engine of respondents is task-dependent and it tends to expand its searching scope accordingly to the task difficulty. This implies that the anchoring effect is more complicated in more difficult cases, and that stated scenarios are not equally treated by respondents. As such, any conclusion of stated choices should be made in full awareness of this important phenomenon.