We show that several factors explain an investor's "style," i.e., the value versus growth orienta­tion of the investor's stock portfolio. First, an investor's style has a biological basis – a pref­erence for value versus growth stocks is partially ingrained in an investor already from birth. Second, investors who a priori are expected to take more financial risk (e.g., men and wealth­ier individuals) have a preference for growth, not value, which may be surprising if the value premium reflects risk. Finally, an investor's style is explained by "life course theory" in that experiences, both earlier and later in life, explain investment style. Investors with adverse macroeco­nomic experiences (e.g., growing up during the Great Depression or entering the job market during a significant economic downturn) and those from a family with lower socio-economic status show a stronger preferences for value investing several decades later in their lives. Our research contributes a new perspective to the long-standing value/growth debate in finance.