By Dino Carpentras

Centre for Social Issues Research, Department of Psychology, University of Limerick

The loop of isolation

One of the problems discussed during the last public meeting of the European Social Simulation Association (ESSA) at the Social Simulation Conference 2021 was the problem of reaching different communities outside the ABM one. This is a serious problem as we are risking getting trapped in a vicious cycle of isolation.

The cycle can be explained as follows. (a) Many fields are not familiar with ABM methods and standards. This results in the fact that (b) both reviewers and editors will struggle in understanding and evaluating the quality of an ABM paper. In general, this translates in a higher rejection rate and way longer time before publication. As results (c) fewer researchers in ABM will be willing to send their work to other communities, and, in general, fewer ABM works will be published in journals of other communities. Fewer articles using ABM makes it such that (d) fewer people would be aware of ABM, understand their methods and standards and even consider it an established research method.

Another point to consider is that, as time passes, each field evolves and develops new standards and procedures. Unfortunately, if two fields are not enough aware of each other, the new procedures will appear even more alien to members of the other community reinforcing the previously discussed cycle. A schematic of this is offered in figure 1.

Figure 1: Vicious cycle of isolation

The challenge

Of course, a “brute force” solution would be to keep sending articles to journals in different fields until they get published. However, this would be extremely expensive in terms of time, and probably most researchers will not be happy of following this path.

A more elaborated solution could be framed as “progressively getting to know each other.” This would consist in modellers getting more familiar with the target community and vice versa. In this way, people from ABM would be able to better understand the jargon, the assumptions and even what is interesting enough to be the main result of a paper in a specific discipline. This would make it easier for members of our community to communicate research results using the language and methods familiar to the other field.

At the same time, researchers in the other field could slowly integrate ABM into their work, showing the potential of ABM and making it appear less alien to their peers. All of this would revert the previously discussed vicious cycle, by producing a virtuous one which would bring the two fields closer and closer.

Unfortunately, such goal cannot be obtained overnight, as it probably will require several events, collaborations, publications and probably several years (or even decades!). However, as result, our field would be familiar to and recognized by multiple other fields, enormously increasing the scientific impact of our research as well as the number of people working in ABM.

In this short communication, I would like to, firstly, highlight the importance and the challenges of reaching out other fields and, secondly, show a practical example with the field of psychology. I have chosen this field for no particular reason, besides the fact that I am currently working in the department of psychology. This gave me the opportunity of interacting with several researchers in this field.

In the next sections, I will summarize the main points of several informal discussions with these researchers. Specifically, I will try to highlight what they reported to be promising or interesting in ABM and also what felt alien or problematic to them.

Let me also stress that this does not want to be a complete overview, nor it should be thought as a summary of “what every psychologist think about ABM.” Instead, this is simply a summary of the discussions I had so far. What I hope, is that this will be at least a little useful to our community for building better connections with other fields.

The elephant in the room

Before moving to the list of comments on ABM I have collected, I want to address one point which appeared almost every time I discussed ABM with psychologists. Actually, it appeared almost every time I discuss ABM with people outside our field. This is the problem of experiments and validation.

I know there was recently a massive discussion on the SimSoc mailing list on opinion dynamics and validation, and this discussion will probably continue. Therefore, I am not going to discuss if all models should be tested, if a validated model should be considered superior, etc. Indeed, I do not want to discuss at all if validation should be considered important within our community. Instead, I want to discuss how important this is while interacting with other communities.

Indeed, many other fields give empirical data and validation a key role, having even developed different methods to test the quality of a hypothesis or a model when comparing it to empirical data (e.g. calculation of p-value, Krishnaiah 1980). Also, I repeatedly experienced disappointment or even mockery when I explained to non-ABM people that the model I was explaining them about was not empirically validated (e.g. the Deffuant model of opinion dynamics). In one single case, I even had a person laughing at me for this.

Unfortunately, many people which are not familiar with ABM end up considering it almost like a “nice exercise,” and even “not a real science.” This could be extremely dangerous for our field. Indeed, if multiple researchers will start thinking of ABM as a lesser science, communication with other fields – as well as obtaining funding for research – would get exponentially harder for our community.

Also, please, let me stress again to not “confuse the message with the messenger.” Here, I am not claiming that an unvalidated model should be considered inferior, or anything like that. What I am saying is that many people outside our field think in a similar fashion and this may eventually turn into a way bigger problem for us.

I will further discuss this point in the conclusion section, however, I will not claim that we should get rid of “pure models,” or that every model should be validated. What I will claim is that we should promote more empirical works as they will allow us to interact more easily with other fields.

Further points

In this section, I have collected (in no particular order) different comments and suggestions I have received from psychologist on the topic ABM. All of them had at least some experience of working side to side with a researcher developing ABMs.

Also in this case, please, remember that this are not my claims, but feedbacks I received. Furthermore, they should not be analysed as “what ABM is,” but more as “how ABM may look like to people in another field.”

1. Some psychologists showed interest in the possibility of having loops in ABMs, which allow for relationships which go beyond simple cause and effect. Indeed, several models in psychology are structured in the form of “parameter X influences parameter Y” (and Y cannot influence X, forming a loop). While this approach is very common in psychology, many researchers are not satisfied with it, making ABMs are a very good opportunity for the development of more realistic models.
2. Some psychologists said that at first impact, ABM looks very interesting. However, the extensive use of equations can confuse or even scare people who are not very used to them.
3. Some praised Schelling’s model (Schelling 1971). Especially the approach of developing a hypothesis and then using an ABM to falsify it.
4. Some criticized that often is not clear what an ABM should be used for or what such a model “is telling us.”
5. Similarly, the use of models with a big number of parameters was criticized as “[these models] can eventually produce any result.”
6. Another confusion that appeared multiple times was that often it is not clear if the model should be analysed and interpreted at the individual level (e.g. agents which start from state A often end up in state B) or at the more global level (e.g. distribution A results in distribution B).
7. Another major complaint was that psychological measures are nominal or ordinal, while many models suppose interval-like variables.
8. Another criticism was based on the fact that often agents behave all in the same way without including personal differences.
9. In psychology there is a lot of attention on the sample size and if this is big enough to produce significant results. Some stressed that in many ABM works it is often not clear if the sample size (i.e. the number of agents) is sufficient for supporting the analysis.

Conclusion

I would like to stress again that these comments are not supposed to represent the thoughts of every psychologist, nor that I am suggesting that all the ABM literature should adapt to them or that they are always correct. For example, to my personal opinion, point 5 and 8 are pushing towards opposite directions; one aiming at simpler models and the other pushing towards complexity. Similarly, I do not think we should decrease the number of equations in our works to meet point 2. However, I think we should consider these feedbacks when planning interactions with the psychology community.

As mentioned before, a crucial role when interacting with other communities is played by experiments and validations. Even points 6 and especially points 7 and 9 suggest how member of this community often try to look for 1-to-1 relationships between agents of simulations and people in the real world.

Figure 2: (left) Empirical ABM acting as a bridge between theoretical ABM and other research fields. (Right) as the relationship between ABM and the other field matures, people become familiar with ABM standards and a direct link to theoretical ABM can be established.

As suggested by someone during the already mentioned discussion in the SimSoc mailing list, this could be solved by introducing a new figure (or, equivalently, a new research field) dedicated to empirical work in ABM. Following this solution, theoretical modellers could keep developing models without having to worry about validation. This would be similar to the work carried out by theoretical researchers in physics. At the same time, we would have also a stream of research dedicated to “experimental ABM.” People working on this topic will further explore the connection between models and the empirical world through experiments and validation processes. Of course, the two should not be mutually exclusive, as a researcher (or a piece of research) may still fall in both categories. However, having this distinction may help in giving more space to empirical work.

I believe that the role of experimental ABM could be crucial for developing good interactions between ABM and other communities. Indeed, this type of research could be accepted much more easily by other communities, producing better interactions with ABM. Especially, mentioning experiments and validation, could strongly decrease the initial mistrust that many people show when discussing ABM. Furthermore, as ABM develops stronger connections with another field, and our methods and standards become more familiar, we would probably also observe more people from the other community which would start looking into more theoretical ABM approaches and what-if scenarios (see fig 2).

References

Krishnaiah, P. R. (Ed.). (1980). A Hand Book of Statistics (Vol. 1). Motilal Banarsidass Publishe.

Schelling, T. C. (1971). Dynamic models of segregation. Journal of Mathematical Sociology, 1(2), 143-186.

Edmonds, B. and Moss, S. (2005) From KISS to KIDS – an ‘anti-simplistic’ modelling approach. In P. Davidsson et al. (Eds.): Multi Agent Based Simulation 2004. Springer, Lecture Notes in Artificial Intelligence, 3415:130–144.

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Carpentras, D. (2020) Challenges and opportunities in expanding ABM to other fields: the example of psychology. Review of Artificial Societies and Social Simulation, 20th December 2021. https://rofasss.org/2021/12/20/challenges/

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© The authors under the Creative Commons’ Attribution-NoDerivs (CC BY-ND) Licence (v4.0)