Ivan Pavlov performed experiments on dogs in which he presented food to them accompanied by the sound of a bell. After doing this repeatedly, the dogs began to salivate when a bell was rung, even if no food was being presented.
In a similar fashion, scientists perform an experiment in which a harmless-looking machine with electrodes is attached to each human participant in the study. Pleasant images are shown to each participant accompanied by a slightly painful electric shock. The participants then react with fear when they see the pleasant images again even if there is no machine to deliver an electric shock.
The researchers find that one participant, Catalina, remembers the images very well but is not afraid when they are presented again. She has not been conditioned. Which of the following is the most valid hypothesis the scientists would want to investigate about Catalina’s brain?