This research has two purposes: (1) to study developmental changes and differences in visual and movement imagery in male and female children and adults; (2) to investigate whether systematic differences in imagery vividness can be measured in specialist groups. In Study 1, the Vividness of Visual Imagery Questionnaire and the Vividness of Movement Imagery Questionnaire were administered to 547 individuals in age groups from 7-8 to 50+ years of age. Significant increases in imagery vividness were found in females at 8-9 and in males at 10-11 years. In general females report more vivid imagery than males but at about 50 females' movement imagery reduced in vividness. In Studies 2-5 imagery differences in specialist groups were examined using the same two questionnaires with a total of 655 participants. In Study 2, children aged 7-15 years with poor movement control were found to be extremely poor imagers with 42 per cent reporting no imagery at all. In Study 3, physical education students reported more vivid imagery than students specializing in physics, English, and surveying. In Study 4, significant differences were found between elite athletes' imagery and that of matched controls. In Study 5, air traffic controllers and pilots were found to have significantly more vivid imagery than matched control groups. Introspective reports of imagery experience show a systematic pattern of relationships with age, gender, and specialization requiring high-level performance of perceptual motor skills. These findings support the theory that mental imagery plays a key role in the planning and implementation of action.