This is a clear example of positive reinforcement. Positive reinforcement involves the addition of a positive stimulus that act as a reinforcement to a desired behavior in order to make the behavior more likely happen again in the future. When Jemma praises and hugs his baby, she is using positive reinforcement, so her baby associates the behavior of saying “thank you” with a reward making him more inclined to say thank you again in the future.
We can conclude that Jemma's reinforcement schedule is positive reinforcement.