Fish and dyscalculia

In this video, we will look further into fish and their role in understanding dyscalculia. As was mentioned in the previous step, if you want to study the genetics behind mathematical abilities you might benefit from a faster growing species, such as fish! Scandalous. Not at all!. Did you know that we did zebrafish, we share at least 70% of our genes? Less than 30% make the difference between Einstein and a small fish! Let’s see some advantages in using fish as a model. They have sufficient physiological complexity and high physiological homology to humans. There is ease of genetic manipulation. Fish reproduce quickly and abundantly.

They experience a rapid development, as they hatch in less than three days and become mature by day 90, making them helpful in studying neurodevelopmental disorders There is high space and the cost-efficiency and excellent potential for screening. And lastly fish have smaller brains which can be better assessed using the newest imaging techniques. Most studies of numerical abilities in fish have been done at the University of Padua. Everything started during my PhD in 2004.

Let’s see how we taught fish to distinguish between the number 2 versus the number 3 Fish were inserted a small tank with two doors and the only way to join their conspecifics was by passing through the door marked with three elements rather than the one we only two (where they couldn’t pass) If they wanted to reach the conspecifics outside, they would have to learn that only one tunnel the one associated to a given numerosity of dots is the one that would permit them to rejoin their social companions! We then controlled for non-numerical variables So some stimuli were controlled for the overall area of the objects Which means that the quantity of Black was the same in both groups.

Another set was controlled for the overall luminance. A third set was controlled for the overall perimeter And others for the convex hull which is the overall space occupied by the most lateral items. By using this procedure, we found for the very first time in the literature that fish can use numerical information! While showing that a fish has numerical abilities is important it still isn’t enough to develop an animal model model for dyscalculia. We need more. We need to show that the cognitive mechanisms underlying fish and humans or at least similar How? By looking at their performance in similar tasks! What does this mean?

If something is easy for human and easy for fish, and something else is difficult for both species. we may suppose that the two species share similar cognitive skills. For this reason, we compared fish and human performance by presenting exactly the same stimuli. We had the two experiments. In the experiment one we studied the role of total numerosity of the items. Basically, we always had the same numerical ratio 1 is to 2. Based on this ratio we presented 4 vs 8 15 vs 30 and 100 vs 200. So what’ changes is the total numerosity of the items. We want to see whether the performance decreases while increasing the total numerosity whether there is an upper limit.

In another experiment, we presented a similar number of items from 20 to 21,

but we change the numerical ratio, from a 1:2 ratio where you have 7 vs 14

to a 3:4 ratio where you have 9 vs 12.

And we found that for fish and the total numerosity is irrelevant meaning that the discriminating 4 vs 8 is as easy as 100 vs 200- But in contrast, numerical ratio is important and discriminating a 1:2 ratio is easier than 3:4 ratio. Once we were able to observe the performance of fish we then presented to humans exactly the same stimuli using a fast numerosity judgment to prevent the use of verbal counting. And these were the results. the numerical systems of humans and fish don’t have an upper limit, meaning that we can discriminate even hundreds of element

with a 1:2 ratio while our accuracy depends on the numerical ratio. See? Fish can not only use numbers but they also apparently use a similar mechanism to quantify objects a fact that has been covered by important media such as the National Geographic! Another way to assess similarities in numerical competence between humans and animals consists in assessing whether animals also have ordinal abilities. Ordinality is the capacity to locate an object on the basis of its numerical position This ability can be very useful in nature.

For instance a bear can find ffood either by using spatial information such as the overall distance from the starting point or by enumerating the trees So food is not behind the first tree nor behind the second one but behind The third tree. We investigated this issue in guppies. This was the apparatus. We wanted to see if they could find a particular feeder in a series of identical ones using only ordinal information. This was the view from above In detail in experiment 1 feeders were placed one after the other in the direction of the current. Food was inserted only in the third feeder.

So we inserted the yellow plates above all the feeders and fish were free to enter the experimental area and remove only one plate. To prevent the possibility that fish could have used spatial cues different special arrangements were presented, so that fish could only use ordinal information. We changed the orientation of the feeders this time in a row perpendicular to the subjects. And the results were much clearer. Subjects selected the third feeder more than by chance And they did NOT select the second or the fourth feeder. So here, guppies seemed to use ordinal information. But we didn’t stop here. We then asked which information is spontaneously encoded by fish.

I mean, in the previous experiment, fish were prevented from using spatial cues. But maybe in nature they use them. So which is spontaneous for fish touse? Spatial or ordinal cues? To address this issue, we set up an experiment where in the training phase, both ordinal and spatial cues were available (by keeping feeders at the same distance). Then in test phase we put in contrast ordinal and spatial information to see which information they use. For example, in the test phase, if guppies use ordinal information they were expected to select this one or this one, if they use spatial information. And we found that fish use both information, although they seem to prefer ordianal information… …

And indeed there is a significant difference between the two conditions. In summary guppies can be trained to use ordinal information. When left free to use ordinal and/or spatial cues they show the ability to use both. The University of Trento with Prof. Vallortigara and the Queen Mary University of London with Prof. Brennan have combined their efforts to study the genetics of numerical abilities in this species model zebrafish. The project is still in progress and unfortunately we cannot summarize the details here. But anyway what is clear is that fish have become the current experimental tool to understand the genetics of dyscalculia. We need to identify genes and assess the relative contribution of the environment in controlled laboratory conditions.

This is the main contribution of fish in the comprehension of the building blocks of our mathematical abilities. The road is long but I believe we are on the right path!