Clark Van Den Berghe and Drs. Chris Porter and Ross Flom, Psychology Department
Without even realizing it, our brain is constantly taking in information from our external environment. While some things take conscious effort, others happen with little or no thought. Vision is an enormous input, and our brain processes what it sees in order for us to do many of our daily activities. One of the things that we process constantly is the number of objects in our field of view. This is the same for both infants and adults, since we both have to navigate the world we live in. The purpose of my research project was to examine more deeply into how exactly our brain processes this information, and to see specifically if this process is similar for infants and adults.
Prior to this project I did some research with Daniel Hyde at Harvard University that initially looked into this question. In one study we discovered using electroencephalography (EEG)/ electric related potentials (ERP) that both adults and infants seem to have two different processes when evaluating numbers: one that is exact for smaller sets of numbers up to three, and another that approximates the exact number for amounts greater than three. In other words, when presented with 1,2, or 3 objects, our brains individually represent those objects, but with higher values the brain approximates the value. The responses also proved to be quite similar between adults and infants, showing that even at an early age, our brains are capable of minimal numerical processing.
This study was very interesting, but it had the limitation of only exploring numbers that were squarely in the range of small number (1,2, and 3) or large number (8 and higher). The specific question I had for my project was: How does the brain process numbers in between, such as 4 and 6?
To examine the question we measured the physiological response to stimuli using electroencephalography (EEG)/event-related potentials (ERP), a commonly used method that passively measures the natural electrical activity on the scalp produced by brain activity. Subjects participated in a 3-minute audio-visual presentation that successively displayed arrays of dots. These arrays varied in number of dots from one to eight and were shown in random sequence. The subsequent event-related response of brain activity following each stimulus presentation was recorded using a net of electrodes placed on the subjects’s head. We did this with two sets of subjects: a group of 16 adults and a group of 16 infants.
The data collection for the adult cohort was relatively simple and easy because it was easy to find volunteers and adults are much more cooperative. However, it was a little more difficult to obtain all the data for the infants. The presentation was not very exciting for 6-month olds, thus we had a high failure rate (about 50%). When this was compounded by other studies going on in the lab, we were not able to finish data collection until early summer after I had already graduated.
Luckily I was able to continue on the project long enough for the data to be collected and prepared for further processing. The results for both groups were averaged and analyzed to examine whether different EEG signatures exist for numerical quantities that surpass the hypothesized boundary of 3, and examined to see how these EEG profiles change in relationship to the change in quantity.
Although the results have not been fully elucidated, the evidence we have at this point is encouraging. With the help of Daniel Hyde we have seen that in adults there is an early response that becomes increasingly larger as the number gets bigger. However, when you break down the EEG into different frequencies you see very high frequency activity (GAMMA) for numbers 1-3 only, not for 4 and 6. Gamma has been traditionally linked to object representation suggesting that something more is going on with the numbers 1-3 compared to larger numbers even though attention is deployed increasingly with number throughout the range.
For infants we see an increase in response as the number increases from 1-3, but 4 and 6 look like the response for 1. This is actually what we predicted to happen, but if they exhibit similar gamma activity to adults, it will provide an interesting insight into how even the infant brain can interpret numbers. If all of these results hold it may suggest that while 1-6 items can be identified separately by the brain, only 1-3 items are being further represented as individual objects.
Participating in this project has been a great experience for me. Not only is there a possible publication that can come from the results, but it has taught me a lot about doing research. Even when you have a good idea, it is not always straightforward in getting the data collected and interpreted. Nonetheless it is a rewarding process and is something I hope to continue to do throughout my career. I am currently in my first year of medical school at Northwestern University, and I am participating in a research project right now. Although it is a different area of study, the research that I did at BYU has helped me cultivate the skills needed to help me be successful.