Pain assessment in children is often challenging due to limitations in developmental level, cognitive ability, or their previous pain experiences. Clinicians must observe physiological and behavioral cues exhibited by the child to make an assessment. Self-report, if possible, is the most accurate measure of pain. Self-report pain scales involve younger kids matching their pain intensity to photographs of other children's faces, such as the Oucher Scale, pointing to schematics of faces showing different pain levels, or pointing out the location of pain on a body outline. Questionnaires for older children and adolescents include the Varni-Thompson Pediatric Pain Questionnaire (PPQ) and the Children’s Comprehensive Pain Questionnaire. They are often utilized for individuals with chronic or persistent pain.