Psychiatrists Alexander Thomas and Stella Chess categorized infant temperament into three primary types: easy, difficult, and slow-to-warm-up. Children with an easy temperament generally exhibit positive emotions, adapt well to change, and can effectively regulate their emotions. Conversely, children with a difficult temperament demonstrate negative emotions and struggle with both adapting to change and emotion regulation; these children are significantly more likely to challenge parents, teachers, and other caregivers (Thomas, 1984).