If you’ve ever found yourself looking at a lengthy restaurant menu and you have not been able to decide what to order for lunch, you have experienced what psychologists call “choice overload”. The brain, in the face of an overwhelming amount of similar choices, struggles to make a decision.

A study conducted at the California Institute of Technology in the United States (Caltech) published in Nature Human Behaviour, with the participation of various institutions including Pompeu Fabra University, reveals new ideas about choice overload, including the parts of the brain responsible for this phenomenon and the options that the brain prefers when making a choice.

“Choice overload can have serious consequences”, says the principal author of the study, Colin Camerer, a professor of Behavioural Economics at Caltech and full professor of the T&C Chen Center for Social and Decision Neuroscience.

Participating with Colin Camerer was Rosemarie Nagel, ICREA research professor with the Department of Economics and Business at UPF, also linked to the Barcelona GSE, an expert in experimental and neuro-economics; Elena Reutskaja, PhD in Economics, Finance and Management from UPF and currently a professor at the IESE Business School; Axel Lindner (Hertie Institute for Clinical Brain Research in Grüneburgweg, Germany), and Richard A.  Andersen (T&C Brain-Machine Interface Center, Caltech).

> Video about the study published by Caltech

Seeking a balance between mental effort and the reward obtained

The study presented to several volunteers images of scenic landscapes that could be printed on an item such as a coffee cup. Each participant was offered a variety of sets of pictures to choose from, containing six, 12 or 24 images.

They were asked to take their decisions while a functional magnetic resonance imaging (fMRI) device recorded brain activity. As a control, volunteers were asked to browse through the images again, but this time the selection of images was made randomly by a computer.

The fMRI scans revealed brain activity in two regions while the participants took decisions: the anterior cingulate cortex (ACC), where the potential costs and benefits of decisions are assessed; and the striatum, a part of the brain responsible for determining the value of things.

The researchers saw that during this activity in the two regions mentioned above was highest in subjects who had twelve options to choose from, and lowest in those with six or 24 items to choose from.

Camerer affirms that the pattern of activity is probably the result of the interaction of the striatum and the ACC and influences the increasing potential of reward (getting an image they really like for their cup) against the increasing amount of effort that the brain will have to make in order to evaluate the possible outcomes.

As the number of options increases, the potential reward increases, but it starts to decrease due to the decrease in profitability. “The idea is that choosing the best of 12 alternatives is probably pretty good, while the jump to choosing from among 24 does not imply a great improvement”, says Camerer. As the options to choose from increase, the effort required to evaluate them increases.

Jointly, the mental effort and the potential reward are located in an agreeable place when the reward is not too low and the effort not too high. This pattern was not seen when the subject only browsed through images because there was no chance of reward and, therefore, it required less effort to evaluate the options.

"The ideal number of options to choose from probably at between 8 and 15, depending on the perceived reward, the difficulty of evaluating these options and the characteristics of each person"

Camerer points out that 12 is not a magic number for human decision-making, but an mechanism of the experimental design. He estimates the ideal number of options to choose from probably at between 8 and 15, depending on the perceived reward, the difficulty of evaluating these options and the characteristics of each person”.

“People tend to feel freer, as if they had more control over their lives, when they have more options to choose from. Essentially, our eyes are bigger than our stomachs”, he says. When we think of how many choices we want, mentally we may not represent the frustrations of making the decision”. Future research in this area could explore and attempt to quantify the mental costs of making a decision. “What is the mental effort? What is the cost of thought? are misunderstood”, claim the researchers.

Adding technology to help understand our decisions

Through the Human Frontier Science Program, which funded a stage at Caltech by Rosemarie Nagel (UPF) and Elena Reutskaja (currently at the IESE Business School) who was then her doctoral student, both co-authors of the study, formed an interdisciplinary group that went ahead with studying this area.

“Even before going to Caltech, by means of questionnaires with undergraduate students on choice overloads Elena Reutskaja and Robin Hoggarth (UPF) developed a theoretical study that posited an increase in the number of choices: subtracting the costs that this posed from the benefits led to an inverted U-shape”, says Rosemarie Nagel.

“Based on the work with Axel Lindner (now a biologist at Tuebingen) and Colin Camerer (Caltech), one of the instigators of neuroeconomics, we have added behavioural study technologies used in medicine to the research, such as magnetic resonance imaging (MRI), to understand these biological aspects of choice overload”, she states.

“Finally, we are now at a stage where we can understand some of our decisions, not only through behavioural choices (revealed preference) or verbal explanations of why we do what we do. In fact, the brain tells us (we already know this from questionnaires or surveys in supermarkets) that it “suffers” from too many choices. fMRI technologies give us more objective data”, concludes Rosemarie Nagel.

Reference work: Elena Reutskaja, Axel Lindner, Rosemarie Nagel, Richard A. Andersen & Colin F. Camerer (October 2018). ”Choice overload reduces neural signatures of choice set value in dorsal striatum and anterior cingulate cortex”. Nature Human Behaviour.