The attraction effect emerges when adding a seemingly irrelevant option (decoy) to a binary choice shifts preference towards a target option. This suggests that choice behaviour is dynamic, i.e., choice values are developed during deliberation, rather than manifesting some pre-existing preference set. Whereas several models of multialternative and multiattribute decision making consider dynamic choice processes as crucial to explain the attraction effect, empirically investigating the exact nature of such processes requires complementing choice output with other data. In this study, we focused on asymmetrically dominated decoys (i.e., decoys that are clearly dominated only by the target option) to examine the attentional and comparative processes responsible for the attraction effect. Through an eye-tracker paradigm, we showed that the decoy option can affect subjects’ preferences in two different and not mutually exclusive ways: by focusing the attention on the salient option and the dominance attribute, and by increasing comparisons with the choice dominant pattern. Although conceptually and procedurally distinct, both pathways for decoy effects produce an increase in preferences for the target option, in line with attentional and dynamic models of decision making. Eye-tracking data provide further details to the verification of such models, by highlighting the context-dependent nature of attention and the development of similarity-driven competitive decisional processes.

Two experiments examined the impact on the decoy effect of making salient thepossibility of post-decision regret, a manipulation that has been shown inseveral earlier studies to stimulate critical examination and improvement ofdecision process. Experiment 1 (N = 62) showed that making regret salienteliminated the decoy effect in a personal preference task. Experiment 2 (N =242) replicated this finding for a different personal preference task and for aprediction task. It also replicated previous findings that externalaccountability demands do not reduce, and may exacerbate, the decoy effect. Weinterpret both effects in terms of decision justification, with differentjustification standards operating for different audiences. The decoy effect, inthis account, turns on accepting a weak justification, which may be seen asadequate for an external audience or one’s own inattentive self butinadequate under the more critical review triggered by making regretpossibilities salient. Seeking justification to others (responding toaccountability demands) thus maintains or exacerbates the decoy effect; seekingjustification to oneself (responding to regret salience) reduces or eliminatesit. The proposed mechanism provides a theoretical account both of the decoyeffect itself and of how regret priming provides an effective debiasingprocedure for it.

Many activities in the new product development requires the decision making to find the final solution from multiple alternatives and make an evaluation. Even methods to support decision maker are available, the decision can go to the wrong direction because of heuristics. “Decoy effect” is a heuristic that appears in a comparison when 2 of 3 alternatives are similar but different in quality. The alternative that is similar but better in quality is possibly selected. The paper aims to understand the decoy effect by investigating it in the pairwise comparison that is a powerful technique for comparing alternatives. In an experiment, 3 ideas for the next generation of apple peeler are compared in pairs with different sequences. An impact of the decoy alternative on the comparison between other two alternatives, is investigated. Results show low impact of the decoy effect in the pairwise comparison, but this effect induces a high chance of selecting the decoy alternative when comparing the results from this study and the previous study by proposing 3 alternatives in the same sequence. Applying pairwise comparison to avoid decoy effect is thus an idea that will be further investigated.

The effect of experimental non-host snail (NHS) communities on the infection of Lymnaea truncatula with Paramphistomum daubneyi and Fasciola hepatica miracidia was studied. The results obtained indicated that NHS had variable effects on basic population parameters of host infection. Specifically, NHS were able to produce aggregation of sporocyst number/snail in the experimental host populations. Proposed hypotheses for decoy effect mechanisms failed to explain completely the experimental results. A new mechanism is suggested, based on a distance response of miracidia to snail chemo-attractants, to explain effects of NHS on miracidial host finding behaviour. It is assumed that miracidia have evolved the ability to discriminate among individual snail chemical attractants in a community already at a distance. This attribute of miracidial behaviour allows NHS to induce variations in the effectiveness of individual host localization by miracidia. The resulting aggregation of successful infections/host is assumed to be the specific component of snail decoy effect at the community level. It was also established that NHS affected trematode reproduction in the host inducing a compensatory increase in the intramolluscan population. Intraspecific competition among developmental stages is suggested to be the mechanism of this compensatory reaction.