When Alice speaks to her six-month-old nephew, her voice immediately takes on a higher pitch, her speech becomes slower, and she begins to use more simplistic words and phrases. This change in Alice's language behavior provides an example of:

Answer: Child-directed speech

Explanation: Child-directed speech is a speech patterns used by parents when communicating with young children, particularly infants, that usually involves simple vocabulary, melodic pitch, repetitive questioning, and a slow or deliberate tempo. However, Child-Directed Speech simply means the physically exaggerated and tonally high-pitched style of speech that adults use when talking to babies and young children.