The Color Discrimination Experiment

Week 1

Today we began light training the three rats using the red colored light bulb as the color for the rats to associate with food. We placed one rat into the cardboard box at a time. When the rat was not next to the hole where the food was presented, we would turn the lamp on and the rat would slowly come over to the hole where the food was. Once the rat started eating, we would turn the light off.

The first couple of days, the rats were not showing any concept of the relationship between the food and the red light.  By day four, there was some major progress in all of the rats. They appeared to make the association between the red light and the food because they would approach the hole a lot quicker when the light was turned on.

Here is a clip of the rats at work. This video shows the rat learning that the food is coming from that corner and won’t move from it

This clip is showing the rat responding to the red light and making the association between that and the food

Week 2

This week, we began using the blue light to train Anastasia. (We decided to use only one rat in the experiment since power was not a concern in this research and we did not have the time to train all three rats for one hour each a day so we chose to work with Anastasia). On the third day of training, we recorded how many responses were correct and incorrect out of 50 trials. Anastasia was able to make 42 correct responses (shown by the blue) and 8 incorrect responses (shown by the red). Here is a pie chart representing the number of correct and incorrect responses made out of  the 50 trials:

rat chart

Here is a video clip of Anastasia responding to the blue light:

After a few days, Anastasia began to show quick responses to the blue light by going to the correct hole to receive the food. So we began  to train her with the yellow light. Here is a clip of Anastasia on her first day with yellow light training:

Week 3

This week we began running our experiment. We have noticed that Anastasia switches each day for the color she will respond to correctly. On the first day, she had the highest response rate for the blue light which was a 70% correct response. The second day, her highest response was tied between blue and yellow with a 60% correct response. On the third day, her highest response was to the yellow light with a 70% correct response (the blue had only a 30% correct response rate). On the fourth day, she had a 90% correct response rate for the yellow and a 30% response rate for the blue. It is important to note that out of all four days, the color red has never had a high response rate. This changed only on the fourth day where she responded correctly to the red light 60% of the time.  Here is a picture of the apparatus we are using in the lab:

This video is showing an incorrect response to the blue light. When she responds incorrectly, we will punish her by picking her up and holding her in the air for a few seconds. Then we place her into the box, positioning her at the correct hole for that light to receive the pellet of food.

This video shows Anastasia responding to the yellow light at the wrong hole. She is responding to the hole where she was last fed (which was the red light hole)

This video shows her correctly responding to the red and yellow lights!

Here is a graph of the data we have compiled from our experiment:

 Our rat did not meet the 80% criterion for any of the colors that we had set up early on in the experiment. However, she was able to discriminate yellow more times than blue and blue more times than red. These results show that she was able to make a discrimination between the yellow and blue lights, but not with the red light since her percentage was below 50%. This indicates that it was most likely due to chance that she went to the red light hole.

According to Bills Samuels, Ph.D., most animals either see no colors, or only see the world as shades of blues and yellows. This can now be applied to a rat’s vision due to the results of our experiment.  Similar to a red-green colorblind human, rat’s can much more easily distinguish between blue and yellow than red. Rats have what is known as dichromatic vision (only green and blue cones) as opposed to humans who have trichromatic vision (blue, green, and red cones). This deficit in their retina is what causes them not to see the red light that we used in our experiment; therefore, yielding these results.

For future research on this topic, it would be nice to have more time to complete the study which would in turn allow more rats to be used. Also, if newer and more equipped technology existed, such as a brain scan, than better understanding of a rat’s eye would be accomplished.

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