Compare methods

	Lawton Ecological Model of Aging	Characteristics Approach to Population Aging
Field	Social Gerontology	Social Gerontology
Family	Process / pipeline	Survival analysis
Year of origin	1973	2013
Originator	M. Powell Lawton & Lucille Nahemow	Warren C. Sanderson and Sergei Scherbov
Type	Ecological theoretical framework for aging and adaptation	Framework for measuring population aging by characteristics rather than chronological age
Seminal source	Lawton, M. P., & Nahemow, L. (1973). Ecology and the aging process. In C. Eisdorfer & M. P. Lawton (Eds.), The psychology of adult development and aging (pp. 619-674). American Psychological Association.	Sanderson, W. C., & Scherbov, S. (2013). The characteristics approach to the measurement of population aging. Population and Development Review, 39(4), 673-685.
Aliases	Competence-Press Model, Ecological Model of Aging, Person-Environment Fit Model, Environmental Docility Hypothesis	Characteristics-Based Aging Measures, Sanderson-Scherbov Characteristics Approach, Alpha-Age Approach, Equivalent-Age Method
Related	3	3
Summary	The Lawton and Nahemow ecological model of aging, also called the competence-press model, is a theoretical framework that explains the behavior and emotional wellbeing of older people as a joint product of their personal capacities and the demands of their environment. Introduced in 1973, it holds that adaptive behavior arises when the level of environmental press matches a person's level of competence, and that mismatches in either direction produce maladaptive behavior and negative affect. Its most famous proposition, the environmental docility hypothesis, states that as individual competence declines the environment exerts proportionally greater influence on behavior, so settings matter most for the most vulnerable. The model introduced the ideas of adaptation level and zones of maximum comfort and maximum performance, giving environmental gerontology a way to think about optimal challenge. It reframed aging not as a property of the person alone but as a transaction between person and place, with direct implications for designing housing, care settings, and communities. The framework remains foundational for environmental and applied gerontology.	The characteristics approach reconceptualizes what it means to be 'old' by measuring age through people's characteristics rather than the number of years since birth. Developed by Warren Sanderson and Sergei Scherbov and set out comprehensively in their 2013 Population and Development Review article, it responds to the fact that conventional aging measures treat a fixed chronological age, such as 65, as a permanent marker of old age even though people at 65 today are healthier and longer-lived than their counterparts decades ago. The core idea is that many relevant attributes, such as remaining life expectancy, health, cognitive function, and disability, vary with both age and time, so old age should be defined by reaching a given level of such a characteristic rather than a fixed birthday. The approach computes equivalent or 'alpha' ages, the ages at which a characteristic takes a chosen reference value, and uses them to build characteristic-based aging indicators. Comparing these with conventional measures often shows that populations are aging more slowly, or even getting younger on some dimensions, than chronological measures suggest. The framework has reshaped how demographers assess the consequences of population aging.