Answer/ Explanation: Scientists can test infants' ability to distinguish different sounds using various methods. Here are a few common approaches:
1. Habituation-Dishabituation: This method involves exposing infants to a repeated sound until they become habituated, meaning they become less interested or responsive to the sound. Then, a new sound is introduced, and if the infant shows renewed interest or a change in response, it suggests that they were able to distinguish between the two sounds.
2. High-Amplitude Sucking (HAS) Procedure: In this procedure, infants are given a pacifier connected to a pressure-sensitive device. The infants' sucking behavior is measured, and they are exposed to different sounds. If the infants show a change in sucking rate in response to different sounds, it indicates their ability to discriminate between the sounds.
3. Head-Turn Preference Procedure: This method relies on infants' natural tendency to turn their heads towards new or interesting stimuli. Infants are presented with different sounds coming from different directions, and their head-turning responses are observed. If the infants consistently turn their heads towards a specific sound, it suggests that they can discriminate between the different sounds.
4. Brain Imaging Techniques: Advanced techniques like electroencephalography (EEG) or functional magnetic resonance imaging (fMRI) can be used to measure brain activity in response to different sounds. By analyzing the neural responses, scientists can determine whether infants can differentiate between various speech sounds.
These methods, along with others, allow scientists to study and understand the development of infants' ability to perceive speech and distinguish different sounds.