Abstract: HAROLD model (Hemispheric Asymmetry Reduction in Older Adults) refers to the phenomenon that brain activation during cognitive performance tends to be less lateralized in older adults than in younger adults. Since the proposal of the model, a lot of studies have been elicited. In recent years, a series of studies have provided much evidence in support of this model from different fields, such as memory, inhibition, language, sense-motor process and brain structure. However, other studies have argued against the model, in particular its explanation of the compensation hypothesis. By analyzing the literatures in light of these two aspects, it is suggested that HAROLD is a task-specific model and that other hypotheses other than the compensation view can also explain the age-related differences in functional brain imaging. A unified operational definition of brain activation could be useful in further clarifying these issues

Key words: cognitive aging, HAROLD, compensation hypothesis, brain imaging