Experiments on the web

This term I finally set some time aside to materialise the interest I have in programming in an experiment on the web. The objective was to explore the potential of conducting experiments online including ‘complex’ interactions with the participants, such as the introduction of games requiring instant calculations such as ‘rock-paper-scissors’ or the provision of feedback from previous rounds. For an example please click here.

The project started with the coding of the experiment ‘from scratch’ on PHP and the associated revision of the data stored on MySQL. Once I finished creating it, I proceeded to ask my 96 first-year students to participate in preparation for a class. It was quite rewarding to find out that all worked as planned and 59 participants took part in this pilot.

Encouraged by the results I then made a few modifications to the code in an effort to make it more efficient and useful on smartphones. Consequently, I then asked to 12 of my second-year students to participate all together at the same time in the experiment on their smartphones. It all worked smoothly! This enables me to set new targets for the next term; that is, integrate new experiments with our recruitment system and conduct proper sessions with the right incentives.

Although the results from the pilot are merely anecdotal, it is always good to find out that they match the predicted behaviour and some might offer new routes for research. In particular, the above-mentioned experiment was on cooperation with heterogeneous endowments and consisted of three stages and two treatments: “Your” and “Another”.

In the first stage, subjects were asked to play 9 rounds of ‘rock-paper-scissors’ and for each time they beat the computer they received one chocolate. In the second stage they were matched with another participant and had to decide whether to send their earnings to this person or not (depending on the treatment this person was from another group or the same group they were).

If anyone decided to send their earnings the amount was doubled. In the third stage the participants only needed to flip a coin twice to earn more chocolates.


There were no treatment differences as about half of the participants on both samples decided to send their endowments. This might be because most of the first-year participants did not have close ties with their colleagues in the group. Moreover, as can be seen in the adjacent Figure the decision to send chocolates was clearly influenced by the amount of chocolates earned in the first stage.


Finally, results from the third stage reveal that the distribution of ‘heads’ reported is biased towards higher numbers (35% in two vs. 25% predicted; 54% in one vs. 50% predicted and 11% in zero vs. 25% predicted).  This clearly might show that participants indeed decided to cheat in this part in an effort to gain more chocolates or compensate for their decision in the second stage.

In retrospect, I think that efforts of this kind should be performed more regularly in Experimental Economics. I am looking forward to the next term when I hope I can conduct new experiments. I will keep you posted!


Antisocial Punishment in Spanish

Have you ever wondered whether culture has an impact on cooperation? When somebody drops rubbish in the streets or plays loud music till late night, would this person be more likely to be told off in Boston or in Athens?

In a recent experiment, Herrmann, Thöni, and Gächter (2008) show that different societies punish peer members differently depending on their inherent social norms for cooperation. For example, in Melbourne people often decide to punish the least cooperative individuals whereas in Muscat punishment is directed at anyone regardless of their cooperative efforts. As a consequence, the benefits of punishment on cooperation appear only in those places where antisocial punishment, i.e. sanctioning of people who behave pro-socially, is relatively low.

Notably, among the 16 cities from their global sample none had a Hispanic background. Given the recent events in those societies involving economic crises, unemployment, violence and the loss of social values and identity, I believe that it is important to quantify how punishment is administered in the region in an effort to understand how cooperation could be improved.

Therefore, this project seeks to replicate the experiment mentioned above in Hispanic societies to gain insights into the cultural differences of the region. It started with an experiment run in Aguascalientes, Mexico, and has continued with one in Granada, Spain.

lab 002

The challenges of conducting research abroad are many, but I believe that particularly in Mexico the fact of not having a dedicated lab was among the greatest. From the recruitment of the participants to the construction of the cubicles and installation of the software on an unstable network of computers that always put the sessions in danger, my experience was rather thrilling.

In the end, thanks to the kind assistance of the Staff at the University of Aguascalientes, the results were even better than expected and 60 subjects took part in the experiment. On the other hand, in Granada the experience was much smoother and the experiment had a total of 48 participants.

cooperationResults show that cooperation differs significantly between the two venues. The first ten periods of this experiment were conducted without punishment available and as it can be seen, the trend is non-increasing in both places. However, once punishment is allowed in the next ten periods, only in Granada cooperation does not take off.


Regarding punishment, the adjacent Figure shows that antisocial punishment surprisingly appears more often in Aguascalientes than in Granada.

Indeed, those results combined might illustrate how the relationship between punishment and cooperation is not linear and that there are many cultural norms that take part in the equation. For instance, punishment does not seem to be effective in Spain regardless of its use whereas in Mexico it tends to boost cooperation regardless of the presence of antisocial punishment. Nevertheless, identifying the potential reasons for such behaviour is something I plan to explore in the associated paper I am currently preparing.


May Fest 2013

In 2013 CeDEx had again the task of representing the School of Economics in the May Fest. This time, we presented two adapted experiments to the visiting families: The Winner’s curse and the Tragedy of the Commons.

2013-05-18 17.08.38

For the first experiment, I worked with my colleague Zahra Murad in an improved version of the experiment presented last year. On this occasion, we posted offers not accepted, profits and losses of the day on a board behind our ‘experimenting desk’. Participants were quite surprised when learning that most of the people attending were actually making losses.

We then explained to our visitors with the aid of a poster what the Winner’s curse was and how it can be related to real-world scenarios.

2013-05-18 12.37.12On the other stand, my colleagues Francesco Fallucci and Simone Quercia presented an adapted version of the Tragedy of the Commons using a fish pond. Here, chocolates represented fish that could double if not taken by the current participant. It was quite fun to see how some parents were trying to (unsuccessfully) persuade their children to not take more than the optimal number of chocolates. In the end, families learned also the importance of a sustainable consumption with some stylized examples presented on a poster.

All in all, this year the May Fest was even more successful than the last one; indeed, I believe that with the right motivation and examples Experimental Economics can be very interesting not only to people within academia. Hopefully, this effort can be improved next year with new experiments and visitors!


Social Structure Summer School

From the 3rd to the 8th of September 2012, I had the opportunity to attend the Social Structure Summer School at the Courant Research Centre “Evolution of Social Behavior”, University of Göttingen, Germany.

In this week-long workshop, Ph.D. students from a wide diversity of fields (such as Biology, Anthropology, Mathematics, Economics and Ethology) had the chance to learn, discuss and integrate their theoretical, observational and experimental approaches for the study of sociality and cooperation.

During the time there, I learned new techniques for the analysis of cooperation that can definitely benefit my own research. Among those, agent-based modelling stood as the most interesting to me.


By receiving training in the use of NetLogo, we were able to create simple models capable of simulating common situations involving cooperation dilemmas. In my case, I worked on a model which tests the survival of strategies in typical coordination-failure games.

For example, the Figure attached shows a starting population of subjects with the following strategies: ‘cooperate’, i.e. always cooperate; ‘defect’, i.e. always defect; ‘tit-for-tat’ and ‘random’. After some iterations, the subjects with the strategy ‘defect’ are the only survivors. This is a common result in the empirical literature.

If you’d like to modify the model’s parameters to test your own hypotheses please go here.

In retrospect, I was glad to meet and interact with Professors and other students who study the evolution of cooperation and are not related to Experimental Economics. There is so much to learn from other approaches! Not surprisingly, the potential for future collaborations is appealing.

SSSS 2012

May Fest

On Saturday 19 May 2012, The University of Nottingham opened its doors for the fourth May Fest, an annual event which aimed to present innovative research from diverse fields to a broader non-academic community.

This year, the School of Economics invited the Centre for Decision Research and Experimental Economics (CeDEx) to participate with some hands-on experiments that could give a glimpse of what we usually study in the lab.

On one of the stands we got assigned, Jeroen Nieboer and I had the opportunity to exemplify with a simple experiment what the Winner’s curse was about.

Specifically, the game designed gave participants the chance to bid for a hypothetical company with the following characteristics:

  • Its current value was equally likely to be an integer number in the 0-100 range and its actual value was determined by a draw from a bingo cage.
  • Purchases occurred only when a bid was greater than the current value.
  • If acquired, the company’s value would increase 1 1/2 times.

Once children and their parents submitted their bids, it was not rare to see them overbid and fall prey of the winner’s curse for reasoning like this: “My guess of the current value of the company  is 50. The value to me will then be one-and-half times this figure, so 75. If I put in a bid below 75 but above 50, say 60, the bid will probably be accepted and I will probably make a profit.”

We then showed them that such logic was not right by presenting examples of the kind: “If your bid of 60 is accepted, that means that the current value of the company is 60 or less. Given this extra information and that each value between 0 and 60 is equally likely, the bidderʼs best guess of the current value is 30. So the expected value to the bidder is 45 and the bidder should expect to make a loss of 15.”

Most of the participants were surprised when they realised that in this game, making a loss was more likely than a profit. But they were even more surprised when some real-world examples were shown.

I think that this was a great experience and also a fantastic opportunity to show to a non-academic community how Behavioural Economics tries to model and experiment with certain anomalies of our choices. Looking forward to the next one!