Wednesday, December 3, 2008

Testing the Memory of Goldfish


I have worked in a pet store for almost all of my adolescence. My job is knowing all the details surrounding the pets that we sell in our store. The one question that a few customers had asked was: exactly how long is the memory of a goldfish? I had no idea. I was given many different answers from different people. One person told me that they had a memory of six minutes. Another said that is was only thirty seconds. I found this all very surprising and that is why I decided to test it myself.

Over the course of three weeks I tested the memory of my goldfish by using two different colored dividers with openings at different locations. I alternated the dividers the first two weeks and then combined them the final week. I wanted to see if the goldfish could first find the opening in the divider, and then remember the position of the opening by associating it with a certain color. If the goldfish were successful in remembering the dividers, they could easily pass through and reach their food on the other side. By recording their times each day I was able to tell if the fish truly recognized each divider and remembered how to get passed them.

Hypothesis: My hypothesis was that the goldfish would not be able to remember the things they learned from the previous day.

Materials and Methods

The subjects in my experiment consisted of eight goldfish ranging in size from 0.7” to 1.5”. Each fish had a unique length and coloration which made them easily distinguishable. They were housed in a ten gallon freshwater aquarium. The pH was at a safe level of 7.0 and the temperature of the water remained at a constant 71 degrees Fahrenheit. Before I began the experiment I wanted the fish to associate the presence of light with their feeding time. Every morning at 9 a.m. when I went to give the fish their food, I would first turn on the fish tank light, and then drop their food in the water on the left side of the fish tank. I proceeded to do this for two weeks prior to the experiment.

The first week of the experiment I continued to feed the fish every morning at approximately 9 a.m. In order to begin the experiment I needed to introduce the first divider into the tank. The first divider was the color green. Its opening was at the bottom right hand corner. First, I placed the divider in the middle of the tank with all eight goldfish on the right side of the divider. Then I proceeded to turn on the fish tank light and drop the fish food on the left side of the divider. I observed the goldfish for a period of fifteen minutes. One by one the goldfish slowly found the opening in the divider and reached their food on the other side. If a goldfish did not find the opening in the designated time, they were forced through the opening with the use of a small fish net. I continued the experiment each morning at approximately the same time for seven days straight.

The second week of the experiment I followed the same procedure of the previous week. The only difference is that I introduced the second divider before feeding. The second divider was the color blue. Its opening was located directly in the center of the divider.

The third and final week of the experiment I followed the same procedure. Instead of introducing a different divider, I placed both dividers one and two into the tank. I placed divider one closest to the goldfish, and divider two closest to the food.

Results and Discussion

I found that the outcome of my experiment to be very successful. Not only did I learn about the fish’s memory, but I learned about how they communicate with one another. I also found that the goldfish even worked in teams to find their food.
In the two weeks before the experiment began, the fish quickly associated the presence of light with feeding time. Each morning, as soon as I turned the light on, all eight fish would be patiently waiting at the left side of the tank.

The first day I introduced the first divider, the fish were a little confused. However after a little bit of time and investigation, the first fish found its way through the opening. After it found food on the other side, it would return to the other fish and signal them to follow. Fishes 2, 3 and 4 observed the first fish’s actions and followed him through the opening. Fishes 5 and 7 stuck together and also investigated the divider. Although they took a little more time, they too found the location of the opening and passed through. Fishes 6 and 8 did not appear to have interest in finding the opening. After the first couple of days I noticed that the fish tended to stay in these same groups each day. Fishes 1,2,3,4 would always stay together. Fishes 5 and 7 would swim together almost every day. Fishes 6 and 8 stuck together for the first few days, but fish 6 decided to leave the eighth fish in order to pursue food. As each day passed, their times seemed to improve. They seemed to remember where the opening was and had no trouble finding food. The only fish that never found the opening was fish number 8.

Table 1. Amount of time it took each fish to reach the opposite side of the tank during the first week of experimentation.

The second week was very interesting. I thought the fish would investigate the new divider, find the new opening and repeat a process similar to the first week. I was very surprised that the goldfish did not investigate the new divider at all. Instead they all remained put in the same corner that the opening of the first divider was located. It seemed as though they were convinced that an opening should have been right where they were swimming. After a few minutes passed, fish number 1 squeezed through a small space between the right side of the divider and the tank wall. The other fish observed this strategy and soon they all followed. Although fish 7 continually tried to fit through the space between the divider and the wall, his body was too large to fit. He did somehow manage to squeeze through two days of the week. Fish 8 still seemed to have no interest in finding food.

Table 2. Amount of time it took each fish to reach the opposite side of the tank during the second week of experimentation.

The third week presented a very tough challenge. The goldfish would have to remember how to pass through both dividers 1 and 2. I really did not think that the fish would be successful in completing this task. I was proved wrong on the very first day. Although it took a longer amount of time, fishes 1,2 and 3 all made their way through both dividers. It took a day or two for the other fish to catch onto the idea, but eventually they all did. The time it took for them to find their way past both dividers improved each day. The only fishes that did not make it through the dividers at all that week were fishes 7 and 8.

Table 3. Amount of time it took each fish to reach opposite time in the third week of experimentation

Not only did my observations confirm that the goldfish had a lasting memory, but the times that I recorded each day seemed to prove it as well. Each day it took the fish less and less time to find their way through the divider. Although the fish did not technically go through the intended opening of the second divider, they still managed to find a way through, and they remembered it each day. When the third week came along, fishes 1,2 and 3 did not only remember how to pass the first divider, but they remembered the second divider as well. Fishes 4,5 and 6 observed their actions and quickly followed the same path. I think this experiment proves that goldfish must have a memory that can last up to weeks and even months. I think it also proves that colors that are present in their environment help them to successfully find food.