Knowledge that Transforms

In the longitudinal study reported here, we examined genetic and caregiving-based contributions to individual differences in infant attachment classifications. For 154 mother-infant pairs, we rated mothers' responsiveness to their 6-month-old infants during naturalistic interactions and classified infants' attachment organization at 12 and 18 months using the Strange Situation procedure. These infants were later genotyped with respect to the serotonin-transporter-linked polymorphic region (5-HTTLPR). Maternal responsiveness uniquely predicted infants' attachment security. Infants' 5-HTTLPR variation uniquely predicted their subtype of attachment security at 12 months and their subtype of attachment insecurity at 12 and 18 months. The short allele for 5-HTTLPR was associated with attachment classifications characterized by higher emotional distress. These findings suggest that 5-HTTLPR variation contributes to infants' emotional reactivity and that the degree to which caregivers are responsive influences how effectively infants use their caregivers for emotion regulation. Theoretical implications for the study of genetic and caregiving influences are discussed.

How do words affect generalization, and how do these effects change during development? One theory posits that even early in development, linguistic labels function as category markers and thus are different from the features of the stimuli they represent. Another theory holds that early in development, labels are akin to other features, but that they may become category markers in the course of development. We addressed this issue in two experiments with 4- to 5-year-olds and adults. In both experiments, participants performed a categorization task (in which they predicted a category label) and an induction task (in which they predicted a missing feature). In the latter task, the category label was pitted against a highly salient feature, such that reliance on the label and reliance on the salient feature would result in different patterns of responses. Results indicated that children relied on the salient feature when performing induction, whereas many adults relied on the category label. These results suggest that early in development, labels are no more than features, but that they may become category markers in the course of development.

In October of 2011, the U.S. Preventive Services Task Force released a draft report in which they recommended against using the prostate-specific antigen (PSA) test to screen for prostate cancer. We attempt to show that four factors documented by psychological research can help explain the furor that followed the release of the task force's report. These factors are the persuasive power of anecdotal (as opposed to statistical) evidence, the influence of personal experience, the improper evaluation of data, and the influence of low base rates on the efficacy of screening tests. We suggest that augmenting statistics with facts boxes or pictographs might help such committees communicate more effectively with the public and with the U.S. Congress.

Adaptation and attention are two mechanisms by which sensory systems manage limited bioenergetic resources: Whereas adaptation decreases sensitivity to stimuli just encountered, attention increases sensitivity to behaviorally relevant stimuli. In the visual system, these changes in sensitivity are accompanied by a change in the appearance of different stimulus dimensions, such as speed. Adaptation causes an underestimation of speed, whereas attention leads to an overestimation of speed. In the two experiments reported here, we investigated whether the effects of these mechanisms interact and how they affect the appearance of stimulus features. We tested the effects of adaptation and the subsequent allocation of attention on perceived speed. A quickly moving adaptor decreased the perceived speed of subsequent stimuli, whereas a slow adaptor did not alter perceived speed. Attention increased perceived speed regardless of the adaptation effect, which indicates that adaptation and attention affect perceived speed independently. Moreover, the finding that attention can alter perceived speed after adaptation indicates that adaptation is not merely a by-product of neuronal fatigue.

We propose that in social interactions, appreciation of a helper depends on that helper's instrumentality: The more motivated one is to accomplish a goal, and the more one perceives a helper as able to facilitate that goal, the more appreciation one will feel for that helper. Four experiments supported this instrumentality-boost hypothesis by showing that beneficiaries felt more appreciation of their helpers while they were receiving help toward an ongoing task than after that task was completed or after the helper was deemed no longer instrumental. This finding held for both the positive side of appreciation (gratitude) and the negative side (feelings of indebtedness) and also across a range of relationships (complete strangers, newly acquainted partners, and friends). This pattern of appreciation is counterintuitive for helpers, and so a mismatch arises between the time courses of beneficiaries' experienced appreciation and helpers' expectations of appreciation.

Self-affirmation produces large effects: Even a simple reminder of one's core values reduces defensiveness against threatening information. But how, exactly, does self-affirmation work? We explored this question by examining the impact of self-affirmation on neurophysiological responses to threatening events. We hypothesized that because self-affirmation increases openness to threat and enhances approachability of unfavorable feedback, it should augment attention and emotional receptivity to performance errors. We further hypothesized that this augmentation could be assessed directly, at the level of the brain. We measured self-affirmed and nonaffirmed participants' electrophysiological responses to making errors on a task. As we anticipated, self-affirmation elicited greater error responsiveness than did nonaffirmation, as indexed by the error-related negativity, a neural signal of error monitoring. Self-affirmed participants also performed better on the task than did nonaffirmed participants. We offer novel brain evidence that self-affirmation increases openness to threat and discuss the role of error detection in the link between self-affirmation and performance.

After amputation, individuals often have vivid experiences of their absent limb (i.e., a phantom limb). Therefore, one’s conscious image of one’s body cannot depend on peripheral input only (Ramachandran & Hirstein, 1998). However, the origin of phantom sensations is hotly debated. Reports of vivid phantoms in the case of congenital absence of the limb show that memory of former body state is not necessary (Brugger et al., 2000). According to one view, phantoms may reflect innate organization of sensorimotor cortices (Melzack, 1990). Alternatively, phantoms could reflect generalization from viewing other people’s bodies (Brugger et al., 2000), a sensorimotor example of the classic theory that understanding oneself follows from understanding the “generalized other” (Mead, 1934, p. 154). Because phantom limbs cannot be stimulated, sensory testing cannot directly compare visual and somatosensory influences on representations of phantom limbs. Consequently, empirical investigation of phantoms is limited.

Theories of why humans forget have been challenged by the newly discovered list-length/output-interference paradox, in which--under certain testing conditions--learning is not harmed by the amount of verbal material studied, whereas retrieval of that material becomes more difficult with increases in the number of items tested. The latter finding is known as output interference, and the results of the experiment reported here indicate that a release from output interference is obtained when the nature of the items is changed during testing. Specifically, when participants are asked to recognize items from two categories, output interference is minimized when items from each category are tested separately in large blocks. This finding supports models of forgetting that assume interference arises from information about the to-be-learned material that is stored in memory; in contrast, this finding is difficult to explain using models that assume forgetting is the result only of changing context.

This study tested whether the timing of first sexual intercourse in adolescence predicts romantic outcomes in adulthood, including union formation, number of romantic partners, and relationship dissatisfaction. Participants were 1,659 same-sex sibling pairs from the National Longitudinal Study of Adolescent Health, who were followed from adolescence (mean age = 16 years) to young adulthood (mean age = 29 years). The timing of participants' first sexual intercourse was classified as early (at age 14 or earlier), on time (between the ages of 15 and 19), or late (at age 19 or older). Compared with early and on-time age at first sex, late age at first sex was associated with decreased odds of marriage or nonmarital cohabitation and fewer romantic partners in adulthood. Among individuals who had married or cohabited with a partner, late timing of first sex was associated with significantly reduced levels of relationship dissatisfaction, even after controlling for genetic and environmental differences between families (using a sibling-comparison model), demographic outcomes in adulthood, and involvement in dating during adolescence. These results underscore the contribution of a life-span approach to our understanding of romantic relationships.