Does unpacking CO2 emissions and visualization of travel itinerary impact travel choice?

How the presentation of information influences human judgment and choice is a central question in cognitive science. Understanding these effects is particularly relevant in contexts such as sustainable decision-making, where individuals often must navigate complex information and uncertain trade-offs. This study investigated how Support Theory and visual specificity can affect willingness to switch from travelling by plane to train. In a smartphone-based experiment, participants (N = 343) first viewed a mock-up booking itinerary for a flight, then estimated global mobility-related CO2 emissions in either a packed or unpacked question format. Subsequently, they were shown a train alternative varying in number of transfers (1 vs. 3) and in visual specificity (step-by-step details vs. no details). Participants in the unpacked condition estimated emissions to be significantly higher than those in the packed condition (F[1, 341] = 79.6; p < .001). Further analysis revealed that, within the 3-transfer condition, those with high confidence were especially responsive to the experimental manipulations, such that highly confident participants were more likely to switch when step-by-step details were shown (M = 55.2% vs. M = 34.0%), t(63) = 3.00, p = .006. A similar effect was observed for unpacking (M = 57.2% vs. 37.9%), t(52) = 3.00, p = .01. These findings suggest that individuals’ confidence in their own judgments plays a critical role in whether unpacking and visual specificity of information translates into actual behavior. While unpacking increases perceived environmental impact, only those confident of their judgment act on this information. Similarly, explicit visual specificity appears to support action among highly confident individuals, potentially by making the journey more concrete and thus actionable. This highlights the importance of tailoring interventions not only to what is presented, but also to how people relate to what they know.