An experiment that I found to be particularly interesting was written by researchers Guttman and Kalish in 1956 entitled Discriminability and Stimulus Generalization. Twenty-four pigeons that were never involved in any previous studies were used during experimentation. An automatic key-pecking box was used as an apparatus. The twenty-four pigeons were divided into groups of six. The researchers trained pigeons to respond to a single, a green-colored key for food. The reinforcement schedule was an average 1-minute variable interval schedule. The pigeon’s pecking behavior was reinforced in the presence of one wavelength light, or hue of colors, on the key. After skill acquisition, they tested the amount of responding to other key colors gradients. Ten wavelengths ranged from blue-green to yellow. When presented with a color that was not very similar to the initial stimulus, responding decreased. When color was similar to the initial stimulus, responding increased.
Guttman and Kalish reported that pigeons were unable to thoroughly discriminate between wavelengths. The Guttman and Kalish experiment demonstrated stimulus generalization, which means that there was responding in the presence of a stimulus that was similar to the initial stimulus used in skill acquisition. The researchers graphed a generalization gradient which showed the relationship between the degree of change in the original stimulus and response strength. They found that responses were highest at the original training stimulus in the generalization