Theresa E. Robertson

The influence of mortality and socioeconomic status on risk and delayed rewards: a life history theory approach.

Why do some people take risks and live for the present, whereas others avoid risks and save for the future? The evolutionary framework of life history theory predicts that preferences for risk and delay in gratification should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced decisions involving risk preference (e.g.,

Environmental Contingency in Life History Strategies: The Influence of Mortality and Socioeconomic Status on Reproductive Timing

10 for sure vs. 50% chance of

Environmental Contingency in Life History Strategies

20) and temporal discounting (e.g.,

When the Economy Falters, Do People Spend or Save? Responses to Resource Scarcity Depend on Childhood Environments

5 now vs.

The financial consequences of too many men: sex ratio effects on saving, borrowing, and spending.

10 later). The effect of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals who grew up relatively poor, mortality cues led them to value the present and gamble for big immediate rewards. Conversely, for individuals who grew up relatively wealthy, mortality cues led them to value the future and avoid risky gambles. Overall, mortality cues appear to propel individuals toward diverging life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors influence economic decisions and risky behaviors.

Facing the future: Memory as an evolved system for planning future acts

Why do some people have children early, whereas others delay reproduction? By considering the trade-offs between using ones resources for reproduction versus other tasks, the evolutionary framework of life history theory predicts that reproductive timing should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced the desire to have children sooner rather than later. The effects of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals growing up relatively poor, mortality cues produced a desire to reproduce sooner--to want children now, even at the cost of furthering ones education or career. Conversely, for individuals growing up relatively wealthy, mortality cues produced a desire to delay reproduction--to further ones education or career before starting a family. Overall, mortality cues appear to shift individuals into different life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors can influence fertility and family size.

The psychosemantics of free riding: dissecting the architecture of a moral concept.

Why do some people have children early, whereas others delay reproduction? By considering the trade-offs between using ones resources for reproduction versus other tasks, the evolutionary framework of life history theory predicts that reproductive timing should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced the desire to have children sooner rather than later. The effects of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals growing up relatively poor, mortality cues produced a desire to reproduce sooner--to want children now, even at the cost of furthering ones education or career. Conversely, for individuals growing up relatively wealthy, mortality cues produced a desire to delay reproduction--to further ones education or career before starting a family. Overall, mortality cues appear to shift individuals into different life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors can influence fertility and family size.

Cross-cultural differences and similarities in proneness to shame: an adaptationist and ecological approach.

Just as modern economies undergo periods of boom and bust, human ancestors experienced cycles of abundance and famine. Is the adaptive response when resources become scarce to save for the future or to spend money on immediate gains? Drawing on life-history theory, we propose that people’s responses to resource scarcity depend on the harshness of their early-life environment, as reflected by childhood socioeconomic status (SES). In the three experiments reported here, we tested how people from different childhood environments responded to resource scarcity. We found that people who grew up in lower-SES environments were more impulsive, took more risks, and approached temptations more quickly. Conversely, people who grew up in higher-SES environments were less impulsive, took fewer risks, and approached temptations more slowly. Responses similarly diverged according to people’s oxidative-stress levels—a urinary biomarker of cumulative stress exposure. Overall, whereas tendencies associated with early-life environments were dormant in benign conditions, they emerged under conditions of economic uncertainty.

The future-orientation of memory: Planning as a key component mediating the high levels of recall found with survival processing

The ratio of males to females in a population is an important factor in determining behavior in animals. We propose that sex ratio also has pervasive effects in humans, such as by influencing economic decisions. Using both historical data and experiments, we examined how sex ratio influences saving, borrowing, and spending in the United States. Findings show that male-biased sex ratios (an abundance of men) lead men to discount the future and desire immediate rewards. Male-biased sex ratios decreased mens desire to save for the future and increased their willingness to incur debt for immediate expenditures. Sex ratio appears to influence behavior by increasing the intensity of same-sex competition for mates. Accordingly, a scarcity of women led people to expect men to spend more money during courtship, such as by paying more for engagement rings. These findings demonstrate experimentally that sex ratio influences human decision making in ways consistent with evolutionary biological theory. Implications for sex ratio effects across cultures are discussed.

The functional independence of trait self-knowledge: Commentary on Sakaki (2007)

All organisms capable of long-term memory are necessarily oriented toward the future. We propose that one of the most important adaptive functions of long-term episodic memory is to store information about the past in the service of planning for the personal future. Because a system should have especially efficient performance when engaged in a task that makes maximal use of its evolved machinery, we predicted that future-oriented planning would result in especially good memory relative to other memory tasks. We tested recall performance of a word list, using encoding tasks with different temporal perspectives (e.g., past, future) but a similar context. Consistent with our hypothesis, future-oriented encoding produced superior recall. We discuss these findings in light of their implications for the thesis that memory evolved to enable its possessor to anticipate and respond to future contingencies that cannot be known with certainty.