Imen Bouhlel

Topic: Individual search 


When to stop searching in a highly uncertain world? A theoretical and experimental investigation of “two-way” sequential search tasks.

with Michela Chessa,  Agnès Festré and Eric Guerci.

In Journal of Economic Behavior and Organization

When to stop exploring is crucial in contexts where learning to manage time and uncertainty is critical for carrying out successful initiatives (e.g., innovation, personnel recruitment, vaccine discovery). We investigate analytically and experimentally the exploration-exploitation trade-offs in such contexts. A “two-way” sequential search task is proposed, where the classical exploration-exploitation trade-off in sequential decisions with finite-horizon is coupled with a further one about discovering the real value of each alternative. The longer the time spent on a specific alternative, the higher the certainty about its expected value but at the higher cost of an under-exploitation of the best alternative so far explored. People learn better when to stop the more certain the information is. A potential behavioral trap in the exploration of “two-way” search tasks is identified that brings towards local optima. We recommend policies that induce people to reduce the time spent exploring the alternatives.


Working papers

Inattention in multi-attribute search : an experiment.

with Bora Lancee and Stephanie Rosenkranz.

Humans do not have infinite attention. Contrary to what traditional economic models would predict, only a subset of all available alternatives are considered for most decisions one makes in a lifetime. On top of this, only a limited number of attributes of these alternatives are taken into account. We study how choices between alternatives and the associated search behavior change when an optimal search strategy is communicated. We do so by implementing a treatment manipulation targeting the amount of search and studying inattention as a moderator. Our experimental study expands the recent work on inattention. We design and implement an online search experiment with a representative UK sample, in which we study the relationship between inattention and the amount of search, and research if we can adjust the amount of search by the communication of an optimal strategy. We find that search behavior is better predicted with partial attention. Additionally, the level of inattention depends on the attribute's importance—the more important the attribute, the higher the level of attention allocated. Secondly, our intervention has a converging effect on search behavior, where so-called "over-searchers" diminish their search while "under-searchers" increase their search levels towards the communicated optimum. Lastly, we find that inattention levels have a moderating role in the shift of search behavior for the group of over-searchers.    


In progress

Theoretical modeling of individual two-attributes sequential search with recall: Example of air-travelling booking behavior.

with Zakaria Babutsidze and Michela Chessa.

We extend the multi-attributes search model of Lim et al (2006, Sequential Search with Multi-Attribute Options, DecisionAnalysis), in which we incorporate the possibility of recalling previously rejected alternatives. We then compare the results of our theoretical model to optimization-based numerical simulations using hill-climbing with random restarts algorithm. Our model can be applied to describe air-traveling booking behavior.

Topic: Collective search


Sharing is not erring : How environments can encourage pseudo-reciprocity in collective human search.

with Charley M. Wu, Nobuyuki Hanaki and Robert L. Goldstone,

In Rogers, M. Rau, X. Zhu, & C. W. Kalish (Eds.) , Proceedings of the 40th Annual Conference of the Cognitive Science Society (pp. 156-161).

Information sharing in competitive environments may seem counterintuitive, yet it is widely observed in humans and other animals. Companies often release technologies under open source license and scientists openly publish their research, often sharing free-to-access versions of their papers, rather than only publishing in restricted access journals. What drives this behavior and in which environments can it be beneficial ? Using simulations in both static and dynamic environments, we show that sharing information can lead to individual benefits through the mechanisms of pseudo-reciprocity, whereby shared information leads to by-product benefits for an individual without the need for explicit reciprocation. Crucially, imitation with a certain level of innovation is required to avoid Roger’s paradox, while the novel mechanism of an local visibility radius allowed for the coordination of self-organizing collectives of agents. When these two mechanisms are present, we find robust evidence for the benefits of sharing–even when others do not reciprocate.


The Evolutionary Dynamics of Cooperation in Collective Search.

with Alan N. Tump, Charley M. Wu and Robert L. Goldstone,

In A. K. Goel, C. M. Seifert, & C. Freksa (Eds.) , Proceedings of the 41th Annual Conference of the Cognitive Science Society (pp. 883–889).

How does cooperation arise in an evolutionary context ? We approach this problem using a collective search paradigm where interactions are dynamic and there is competition for rewards. Using evolutionary simulations, we find that the unconditional sharing of information can be an evolutionary advantageous strategy without the need for conditional strategies or explicit reciprocation. Shared information acts as a recruitment signal and facilitates the formation of a self-organized group. Thus, the improved search efficiency of the collective bestows byproduct benefits onto the original sharer. A key mechanism is a visibility radius, where individuals have unconditional access to information about neighbors within a limited distance. Our results show that for a variety of initial conditions—including populations initially devoid of prosocial individuals—and across both static and dynamic fitness landscapes, we find strong selection pressure to evolve unconditional sharing.


In progress

Now you see me, now you don’t : Effect of local visibility on information sharing behavior in competitive collective search.

With Alan N. Tump, Charley M. Wu, Nobuyuki Hanaki and Robert L. Goldstone.

Information sharing in competitive environments is a phenomenon observed in both humans and animals. Companies often release their technologies and innovations under an open-source license, allowing free access to their work, and taking the risk to see others benefiting from it by copying or building upon it, without bearing its costs. Many animal species also signal the location of the food that they find to their conspecifics, increasing the competition for it. We study the drivers and determinants of this behavior.  Using agent-based simulations, we show that sharing information can lead to individual benefits through the mechanisms of pseudo-reciprocity, without the need for explicit reciprocation, as long as the followed search strategy entails imitation with a certain level of innovation.  We also find using evolutionary simulations that the unconditional sharing of information can be an evolutionary advantageous strategy without the need for conditional strategies or explicit reciprocation. We test the results of the model experimentally with human subjects and find the local visibility mechanism improves individual performance and gives rise to sharing benefits. Learning is however essential in order to observe these benefits.  We also find that participants sharing behavior is conditional on the observed rewards, where they tend to withhold information about higher rewards. 

Topic: Innovation Diffusion

Working Papers

Competitive diffusion and sustainable transitions: the case of plastics recycling technologies.

with Nathalie Lazaric and Paolo Zeppini.

Climate change confronts modern societies with numerous challenges requiring the emergence of innovative technologies. Often, emerging sustainable technologies face the barrier of mature and environmentally unsustainable counterparts. Even novel sustainable concepts and practices, such as recycling, can be hindered by the adoption and diffusion of outdated polluting technologies, jeopardizing the widespread adoption of innovative sustainable solutions. It is crucial to understand the mechanism of diffusion to design policies enabling the establishment of promising yet underdeveloped technologies. We propose an agent-based model of competitive diffusion with learning based on percolation theory, where adoption occurs in a social network through word-of-mouth. We investigate how learning affects diffusion and competition and find that small differences in technology costs lead to large differences in diffusion size. Most importantly, increasing the number of initial adopters may hamper overall diffusion, due to competition. Our model captures several stylized facts of plastics waste recycling, where mechanical and physical/chemical technologies are being adopted as alternative solutions.


In progress

Modelling innovation diffusion using non-monotonic percolation.

with Nathalie Lazaric and Paolo Zeppini.

Diffusion is a crucial element of structural change in the economy and in societies in general. Indeed, the success of an innovation depends not only on its intrinsic properties, but also on its diffusion process. Diffusion processes are pervasive to many realms of society, from technological change to people behaviours. Social structure is a key element driving diffusion process, and the academic literature on networks has shown how the non-linearity of diffusion matters for the adoption of innovative products or behaviours by potential adopters. This is true at different stages of the value chain of an economy, so in particular for consumers but also for producers. We propose a model of diffusion based on the percolation framework, which is inspired from physics, and which has proven to be meaningful to show the criticality of diffusion processes by characterising their features of phase transitions. We build on the work of Zeppini and Frenken (2018,  Artificial Societies and Social Simulation) to model the adoption and diffusion of an innovative product, as an alternative of its competitor, already adopted by the social network of producers. We introduce additional dimensions for adoption by a node in the network and we allow for trade-offs between the different dimensions. Introducing such trade-offs causes a non-monotonic behaviour of the model, where the percolation critical transition is experienced twice, first in one direction, going through the diffusion phase, and then in the opposite direction, falling back in the no-diffusion regime.

Other topics

Working Papers

Cognitive hysteresis in a repeated ultimatum game.

with Eric Guerci and Alan Kirman.

Decision inertia is a widely observed phenomenon in many real life situations, particularly under uncertainty. It consists of the tendency to repeat previous choices regardless of whether their past outcome was advantageous or not (Alós-Ferrer et al., 2016; Dutt and Gonzalez, 2012; Sautua, 2017; Jung and Dorner, 2018). This reluctance to incorporate new information in choices thus gives rise to perseveration in the same, possibly suboptimal choices. This phenomenon is a well-known phenomenon in judgement and decision-making research (Erev and Haruvy, 2016), and a number of studies show that decision inertia can explain many decision-making anomalies and suboptimal economic decision-making such as disadvantageous economic belief-updating (Alós-Ferrer et al., 2016; Charness and Levin, 2005), suboptimal investment decisions (Sandri et al., 2010), or the competitive sale dilemma (Liu, 2018).  Our interest is in the mechanisms at work in the short term and how these may lead people to persist in certain judgments or decisions depending on their own recent decisions and their related experience. More particularly, we focus on inertia in a particular type of decision-making, that is decision-making in the presence of strategic interactions, and we are interested in how the perception of fairness can be context-dependent. In a series of experiments, we want to analyze subjects’ judgments as to what they judge to be acceptable offers in repeated ultimatum games and analyze the extent to which there is evidence of adaptation to previous experience resulting in short-term hysteresis or inertia .

In progress

Consumers' willingness-to-pay for recycled plastic products: a choice experiment

with Nathalie Lazaric and Michela Chessa.

We study consumers' willingness-to-pay for plastics-based products depending on a set of attributes such as the type of plastics, whether it is recycled, and the recycling technology. To do that, we use a lab-in-the-field choice experiment with both hypothetical and real choices. We manipulate the presence of trade-offs between the quality of the recycled material and its environmental impact.

Changing eating habits while preserving ecological biodiversity: results from an international survey on Sarpa salpa

with Nathalie Lazaric, Antonia Chiaino, Valentina Asnaghi, Mariachiara Chiantore, Stela Ruci, Sajmir Beqiraj, Cécile Sabourault, Simona Bussotti and Luisa Mangialajo.

The aim of this paper is to observe consumer’s trade-off between environmental values and disposition to change their eating habits. Thus, the conservation of large brown algae forests is a key issue for marine local biological ecosystems as well as the desire to consume local fish and test the willingness of citizens to change their eating habits. Faced with the enormous challenges of biodiversity loss, due to the increase (in number of species and abundance) of herbivorous fish, regulation of their populations must be considered. One solution is to valorise herbivorous fish locally by promoting their consumption, including all stakeholders from the local chain involved and fisheries activities (from fishermen to restaurants and supermarkets, among others). Conservation of Mediterranean Cystoseira sensu lato forests may locally depend on a better and sustainable regulation of Salemas (Sarpa salpa), the only native strict herbivorous fish. An increase in consumption of this local fish with a change in eating habits, together with the awareness to make a sustainable choice, is a way to regulate the population and decrease pressure on large brown algae forests (Gianni et al., 2017). To face this challenge, we carried out a survey in the Mediterranean basin of southern France (Nice region), northern Italy (Genoa region) and Albania (Tirana, Durres and Vlora regions) to observe the knowledge and willingness of citizens to change eating habits in favour of local fish, and more particularly, their knowledge and potential consumption of Sarpa salpa.