In this third instalment of the Sir David Amess UK Children’s Parliament on animal welfare, Professor Gillian Forrester, a leading research scientist, joins young MPs to explore the psychology and emotions of animals. Drawing on her studies of great apes, she explains how species such as gorillas, chimpanzees, and orangutans experience fear, stress, and even post-traumatic stress disorder, often hidden behind behaviours mistaken for calm or even smiles. She highlights the deep evolutionary connections between humans and other primates, emphasising our shared capacity for suffering and the urgent need for empathy. Forrester discusses the rehabilitation of traumatised animals, the importance of enrichment and sanctuary care, and voices her support for Herbie’s Law, a proposed roadmap to end live animal testing in the UK. Blending science, compassion and children’s probing questions, this episode reveals how understanding animal minds can reshape how society treats them.