The American baseball player Satchel Paige, who pitched professionally well into his 40s at a time when that was unheard of, used to ask a simple question: "How old would you be if you didn't know how old you were?"
I have been asking myself that question for years. The honest answer keeps changing. At 35, I felt about 28, still surprised to find myself with adult responsibilities. At 45, I felt closer to 50: heavier somehow, more aware of time. At 52, something strange happened and I felt younger again, more curious, less self-conscious, lighter. The number on my birth certificate and the number I felt myself to be kept diverging.
This is not just a personal curiosity. It is, as it turns out, a significant area of research.
Developmental psychology distinguishes at least four distinct senses of "age." Understanding the differences between them can be genuinely illuminating.
Mental Age is the traditional measure: cognitive ability, IQ, accumulated knowledge, and what we'd now call emotional intelligence. Mental age does not track chronological age in any simple way. Some 70-year-olds have more mental flexibility than some 30-year-olds. Intellectual curiosity, it turns out, is one of the strongest predictors of cognitive longevity.
Biological Age is what's happening inside the body: telomere length, inflammation markers, cardiovascular health, metabolic rate. This is the age your doctor is really measuring. Fauja Singh completed a marathon at 101. His biological age, the age his cells, heart, and lungs were operating at, was plainly not 101 in any meaningful sense. Biological age can be meaningfully altered by lifestyle, stress, sleep, and exercise in ways that chronological age cannot.
Sociocultural Age concerns the roles you occupy and whether they match cultural expectations. Bernice Neugarten's "social clock," the widely shared sense of when things should happen, shapes how "old" or "young" we feel in relation to our milestones. A 35-year-old who has not yet had children in a culture where that is the norm may feel "behind." A 35-year-old in a culture where this is unremarkable may feel entirely on time. The clock is cultural, not biological.
Felt Age / Perceived Age is the age you actually experience yourself to be, influenced by health, mental state, vitality, and how you're treated by others. Research consistently shows that most adults, once past about 25, feel younger than their chronological age. The gap tends to widen with time: people in their 60s often feel 10–15 years younger than they are. This is not denial. It may, in fact, be good health.
One of the most consistent and counterintuitive findings in gerontology is that subjective wellbeing often improves with age, even as objective health declines. Older adults develop more sophisticated strategies for emotional regulation. They invest in fewer, higher-quality relationships. They care less about what strangers think of them. The inner life gets richer even as the outer life contracts. The felt age data reflects this: most older adults feel better about themselves than middle-aged adults do, which is exactly the opposite of what younger people predict.
The Blobs of Six framework is built around chronological age, the most objective measure available for a framework meant to be broadly applicable. But the four ages are a useful reminder that the Blob you're in chronologically is not necessarily the Blob you're living.
Some people in their early 50s are biologically and mentally decades younger than their birth certificates suggest. Some people in their late 30s are carrying the weight of a much longer life. The framework is a starting point, not a verdict.
Satchel Paige's question, then, is actually the right one to start with: How old would you be if you didn't know how old you were? And what does that gap between the number and the feeling tell you about how you're living?