Method to our madness


            Participant will be one female albino Sprague-Dawley lab rat.  She will be twelve weeks old when used in the experiment. She will be housed individually in a small rat cage and she will receive 10 grams of food instead of 15 grams to increase responding during the experiment. The participant will be treated according to APA ethical guidelines.


            For this study, we will use a 25 cm. by 30 cm. cardboard box with a height of 45 cm. It will have a 1 cm. diameter hole on each side, with the exception of one side. We will also use three different colored 60 watt light bulbs, which will be red, blue, and yellow. The perception of red light compared to the perception of yellow light of the same intensity makes the red light seem much less bright than the yellow even though they are equally intense due to the varying wavelengths. The same diminished perception of blue light applies at the other end of the spectrum. The light bulbs will be positioned 50 cm. above the floor of the box. The experiment will also require food pellets.


            The independent variable of this experiment will be the brightness of the light bulb used, which we will control by using the different wavelengths of color. The dependant variable will be responses made by the rat at the hole that has been paired with each wavelength. Responses will be defined by the rat touching any of the holes with her nose and mouth.

            The rat will be conditioned to associate the different wavelengths (red, yellow, and blue) of each light bulb with a different location within the cardboard box from which to receive food. As each light is on, food will be presented through a specified hole; the light gets turned off once the rat receives her reinforcement. Each light (red, yellow, and blue) will be designated to a specific hole. For one week, the rat will be trained to associate one light with its specified hole. This will be done through 50 trials sessions per day where the light is turned on until the rat responds to the correct hole to receive her food. After the three weeks (one week for each light) of training are complete, the researchers will begin presenting all three color wavelengths. There will be 33% of trials with the red (neutral) light, 33% with blue (least bright) light, and 33% with yellow (brightest) light; they will be presented in no particular order. Trials in which the rat responds appetitively at the incorrect hole for the brightness of light will result in no reinforcement (food pellet) for the rat. Successful discrimination between wavelengths will be defined by a criterion of 80% correct responses.

This is a picture of the apparatus used:


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