The generalist genes hypothesis implies that general cognitive ability (g) is an essential target for understanding how genetic polymorphisms influence the development of the human brain. Using 8791 twin pairs from the Twins Early Development Study, we examine genetic stability and change in the etiology of g assessed by diverse measures during the critical transition from early to middle childhood. The heritability of a latent g factor in early childhood is 23%, while shared environment accounts for 74% of the variance. In contrast, in middle childhood, heritability is 62% and shared environment accounts for 33%. Despite increasing importance of genetic influences and declining influence of shared environment, similar genetic and shared environmental factors affect g from early to middle childhood, as indicated by a cross-age genetic correlation of 0.57 and a shared environmental correlation of 0.65. These findings set constraints on how genetic and environmental variation affects the developing brain.
Cognitive Ability; Genetics; Intelligence; Childhood Development
Existing stereotypes about Black Americans may influence perceptions of intent during financial negotiations. In this study, we explored whether the influence of race on economic decisions extends to choices that are costly to the decision maker. We investigated whether racial group membership contributes to differential likelihood of rejection of objectively equal unfair monetary offers. In the Ultimatum Game, players accept or reject proposed splits of money. Players keep accepted splits, but if a player rejects an offer, both the player and the proposer receive nothing. We found that participants accepted more offers and lower offer amounts from White proposers than from Black proposers, and that this pattern was accentuated for participants with higher implicit race bias. These findings indicate that participants are willing to discriminate against Black proposers even at a cost to their own financial gain.
decision making; implicit race bias; behavioral economics; Ultimatum Game; racial and ethnic attitudes and relations; intergroup dynamics; prejudice; social behavior
Evidence suggests that children’s self-perceptions of their abilities predict their school achievement even after one accounts for their tested cognitive ability (IQ). However, the roles of nature and nurture in the association between school achievement and self-perceived abilities (SPAs), independent of IQ, is unknown. Here we reveal that there are substantial genetic influences on SPAs and that there is genetic covariance between SPAs and achievement independent of IQ. Although it has been assumed that the origins of SPAs are environmental, this first genetic analysis of SPAs yielded a heritability of 51% in a sample of 3,785 pairs of twins, whereas shared environment accounted for only 2% of the variance in SPAs. Moreover, multivariate genetic analyses indicated that SPAs predict school achievement independently of IQ for genetic rather than environmental reasons. It should therefore be possible to identify "SPA genes" that predict school achievement independently of "IQ genes."
Caregiving touch has been shown to be essential for the growth and development of human infants. However, the physiological and behavioral mechanisms that underpin infants’ sensitivity to pleasant touch are still poorly understood. In human adults, a subclass of unmyelinated peripheral nerve fibers has been shown to respond preferentially to medium-velocity soft brushing. It has been theorized that this privileged pathway for pleasant touch is used for close affiliative interactions with conspecific individuals, especially between caregivers and infants. To test whether human infants are sensitive to pleasant touch, we examined arousal (heart rate) and attentional engagement (gaze shifts and duration of looks) to varying velocities of brushing (slow, medium, and fast) in 9-month-old infants. Our results provide physiological and behavioral evidence that sensitivity to pleasant touch emerges early in development and therefore plays an important role in regulating human social interactions.
infant development; cognitive development; social interaction
Research on the “emotional brain” remains centered around the idea that emotions like fear, happiness, and sadness result from specialized and distinct neural circuitry. Accumulating behavioral and physiological evidence suggests, instead, that emotions are grounded in core affect – a person's fluctuating level of pleasant or unpleasant arousal. A neuroimaging study revealed that participants' subjective ratings of valence (i.e., pleasure/displeasure) and of arousal evoked by various fear, happiness, and sadness experiences correlated with neural activity in specific brain regions (orbitofrontal cortex and amygdala, respectively). We observed these correlations across diverse instances within each emotion category, as well as across instances from all three categories. Consistent with a psychological construction approach to emotion, the results suggest that neural circuitry realizes more basic processes across discrete emotions. The implicated brain regions regulate the body to deal with the world, producing the affective changes at the core of emotions and many other psychological phenomena.
Metacognition can be defined as knowing what one knows, and the question of whether nonhuman animals are metacognitive has driven an intense debate. We tested three language-trained chimpanzees in an information-seeking task in which the identity of a food item was the critical piece of information needed to obtain the food. In two experiments, the chimpanzees were significantly more likely to visit a container first on trials in which they could not know its contents but were more likely to just name the item without looking into the container on trials in which they had earlier seen the contents of that container. Thus, chimpanzees showed efficient information-seeking behavior that suggested they knew what they had or had not already seen when it was time to name a hidden item.
metacognition; chimpanzees; Pan troglodytes; information-seeking
Visual working memory (VWM) representations influence attention and gaze control in complex tasks, such as visual search, that require top-down selection to resolve stimulus competition. VWM and visual attention clearly interact, but the mechanism of that interaction is not well understood. Here we demonstrate that VWM representations of object features influence the spatiotemporal dynamics of extremely simple eye movements, in the absence of stimulus competition or goal-level biases. The reach of VWM therefore extends into the most basic operations of the oculomotor system.
Visual Memory; Eye Movements; Visual Attention; Visual Perception
Researchers assert that affective responses to seemingly minor daily events have long-term implications for mental health, yet this phenomenon has rarely been investigated. In the current study, we examined how levels of daily negative affect and affective reactivity in response to daily stressors predicted general affective distress and self-reported anxiety and depressive disorders 10 years after they were first assessed. Across eight consecutive evenings, participants (N = 711; age = 25 to 74 years) reported their daily stressors and their daily negative affect. Increased levels of negative affect on nonstressor days were related to general affective distress and symptoms of an affective disorder 10 years later. Heightened affective reactivity to daily stressors predicted greater general affective distress and increased likelihood of reporting an affective disorder. These findings suggest that the average levels of negative affect that people experience and how they respond to seemingly minor events in their daily lives have long-term implications for their mental health.
Some individuals have very specific and differentiated emotional experiences, such as anger, shame, excitement, and happiness, whereas others have more general affective experiences of pleasure or discomfort that are not as highly differentiated. Considering that individuals with major depressive disorder (MDD) have cognitive deficits for negative information, we predicted that people with MDD would have less differentiated negative emotional experiences than would healthy people. To test this hypothesis, we assessed participants' emotional experiences using a 7-day experience-sampling protocol. Depression was assessed using structured clinical interviews and the Beck Depression Inventory-II. As predicted, individuals with MDD had less differentiated emotional experiences than did healthy participants, but only for negative emotions. These differences were above and beyond the effects of emotional intensity and variability.
emotions; depression; happiness; emotional control; individual differences
Recurrent uncontrollable negative thoughts are a hallmark of depressive episodes. Deficits in cognitive control have been proposed to underlie this debilitating aspect of depression. Here, we used functional neuroimaging during an emotional working memory (WM) task to elucidate the neural correlates of these difficulties in cognitive control. In a WM manipulation involving depressed participants, the dorsal anterior cingulate and parietal and bilateral insular cortices were activated significantly more when negative words were removed from WM than when they were maintained in WM; in contrast, nondepressed participants exhibited stronger neural activations in these regions for positive than for negative material. These findings implicate anomalous activation of components of the task-positive network, known to be modulated by cognitive effort, in depression-associated difficulties in expelling negative material from WM. Future studies should examine the association between these aberrations and the maintenance of depressive symptoms.
depression; functional MRI; working memory; dorsal anterior cingulate cortex; insula; neuroimaging; brain
Children use syntax to guide verb learning. We asked whether the syntactic structure in which a novel verb occurs is meaningful to children even without a concurrent scene from which to infer the verb’s semantic content. In two experiments, 2-year-olds observed dialogues in which interlocutors used a new verb in transitive (“Jane blicked the baby!”) or intransitive sentences (“Jane blicked!”). Children later heard the verb in isolation (“Find blicking!”) while watching a one-participant and a two-participant event presented side-by-side. Children who had heard transitive dialogues looked reliably longer at the two-participant event than did those who had heard intransitive dialogues. This effect persisted even when children were tested on a different day, but disappeared when no novel verb accompanied the test events (Experiment 2). Thus, 2-year-olds gather useful combinatorial information about a novel verb based simply on hearing it in sentences, and later retrieve that information to guide verb interpretation.
Control over interference is a pervasive feature of cognitive life. Central to research on interference control has been the identification of its underlying mechanisms. Investigations have focused on processes that filter out distracting perceptual information, leading to negative priming, and processes that discard intruding memories that cause proactive interference. Theories differ regarding whether or not a single process during episodic retrieval underlies both negative priming and the resolution of proactive interference. Using functional magnetic resonance imaging, we combined both phenomena into a single paradigm and found that occipital cortex shows activation uniquely related to negative priming, whereas activation increases in left lateral prefrontal cortex are uniquely associated with proactive interference. This pattern of results contradicts theories that rely on a single process to account for both phenomena. However, results also showed common recruitment of right dorsolateral prefrontal cortex and parietal regions and therefore suggest that some control processes are shared.
Recent experiments suggest that infants’ expectations about agents’ actions are guided by a principle of rationality: in particular, infants expect agents to pursue their goals efficiently, expending as little effort as possible. However, these experiments have all presented infants with infrequent or odd actions, leaving the results open to alternative interpretations and making it difficult to determine whether infants possess a general expectation of efficiency. Here we devised a critical test of the rationality principle that did not involve infrequent or odd actions. In two experiments, 16-month-olds watched events in which an agent faced two identical goal objects; although both objects could be reached by typical, everyday actions, one object was physically (Experiment 1) or mentally (Experiment 2) more accessible than the other. In both experiments, infants expected the agent to select the more accessible object, providing new evidence that infants possess a general and robust expectation of efficiency.
Rationality; Efficiency; Goals; Psychological reasoning; Infant cognition
Recent studies have demonstrated that brief periods of training facilitate the ability to overcome distraction upon future encounters with a given task, and these effects have been proposed to rely on relational memory systems that enable individuals to link specific attentional states to their learned context. In the current work we examined whether medial temporal lobe (MTL) structures critical for relational and contextual learning participate in driving these effects. A group of amnesic patients with bilateral MTL damage and a group of matched comparisons both completed an attentional capture task in which a brief training session typically leads to decreased distraction in a subsequent testing session. Whereas comparisons showed normal training-related decreases in distractibility, amnesic patients did not, indicating that MTL-mediated learning plays a critical role in the ability to use past experience to overcome distraction. This suggests a tight linkage between MTL-dependent relational learning mechanisms and cognitive control.
Attentional Capture; Relational Memory; Medial-Temporal Lobe; Distraction; Amnesia
Could you find one of your 1000 Facebook friends in a crowd of 100? Even at rates of 20–40 comparisons/sec, determining that no friends were in the crowd would take ~40–50 minutes if memory and visual search interacted linearly. Our observers memorized pictures of 1–100 targets and then searched for any target in visual displays of 1–16 objects. Response times varied linearly with visual set size but l–16 accurately predicted response times for different observers holding 100 objects in memory. The results could support a binary representation of visual objects in memory and are relevant to applied searches in which experts look for any of many items of interest (e.g. medical or airport screening tasks).
Physical activity enhances cognitive performance, yet individual variability in its effectiveness limits its widespread therapeutic application. Genetic differences might be one source of this variation. For example, carriers of the methionine-specifying (Met) allele of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have reduced secretion of BDNF and poorer memory, yet physical activity increases BDNF levels. To determine whether the BDNF polymorphism moderated an association of physical activity with cognitive functioning among 1,032 midlife volunteers (mean age = 44.59 years), we evaluated participants’ performance on a battery of tests assessing memory, learning, and executive processes, and evaluated their physical activity with the Paffenbarger Physical Activity Questionnaire. BDNF genotype interacted robustly with physical activity to affect working memory, but not other areas of cognitive functioning. In particular, greater levels of physical activity offset a deleterious effect of the Met allele on working memory performance. These findings suggest that physical activity can modulate domain-specific genetic (BDNF) effects on cognition.
BDNF; physical activity; working memory; executive function; genetics; visual memory; episodic memory
This research evaluated how well overall levels of positive engagement in adolescents’ families of origin, as well as adolescents’ unique expressions of positive engagement in observed family interactions, statistically predicted marital outcomes approximately 20 years later. Data for family-of-origin positive engagement were drawn from approximately 400 families participating in the Iowa Youth and Families Project (IYFP) during three waves of data collection from 1989 to 1991. The primary outcomes were based on data from the IYFP in 2007 to 2008 and included marital behavior from 288 individuals and their spouses. Individuals’ unique family-of-origin expressions of positive engagement were linked to the degree of positive engagement they exhibited towards their spouses. A positive family climate during adolescence for one partner was also associated with marital outcomes for both partners. Overall, the results suggest that a positive climate in the family of origin may have long-term significance for subsequent interpersonal relationships.
Marital distress and conflict are linked to poor physical health. Here, we used behavior genetic modeling to determine the etiology of this association. Biometric moderation models were used to estimate gene-by-environment interaction in the presence of gene-environment correlation between marital satisfaction and self-reported health. Using a sample of 347 married twin pairs from the Midlife in the United States study, we found that genetic influences on the variation in self-reported health were greatest at both high (h2 = .30) and low (h2 = .38) levels of marital satisfaction, with the lowest levels of heritability estimated for participants at the average level of marital satisfaction (h2 = .10). These findings are evidence of the orchid effect: the idea that genetic influences on a phenotype such as physical health are enhanced in nonnormative—both unusually positive and unusually negative—environmental contexts.
health; relationship quality; behavior genetics
Although evidence suggests that attachment anxiety may increase risk for health problems, the mechanisms are not well understood. Married couples (N = 85, Mage = 38.67) provided saliva samples over three days and blood samples on two occasions. Participants with higher attachment anxiety produced more cortisol and had fewer numbers of CD3+ T-cells, CD45+ T-cells, CD3+CD4+ helper T-cells, and CD3+CD8+ cytotoxic T-cells than those with lower attachment anxiety. Higher cortisol was also related to fewer numbers of CD3+, CD45+, CD3+CD4+, and CD3+CD8+, which is mechanistically consistent with research showing that cortisol alters the cellular immune response. These data suggest that attachment anxiety may have physiological costs and provide a glimpse into the pathways through which social relationships impact health. The current study also extends attachment theory in an important new direction by utilizing a psychoneuroimmunological approach to the study of attachment anxiety, stress, and health.
Attachment theory; attachment anxiety; marriage; chronic stress; cortisol; psychoneuroimmunology; psychoneuroendocrinology
Deficits in memory for everyday activities are common complaints among healthy and demented older adults. The medial temporal lobes and dorsolateral prefrontal cortex are both affected by aging and early-stage Alzheimer's disease, and are known to influence performance on laboratory memory tasks. We investigated whether the volume of these structures predicts everyday memory. Cognitively healthy older adults and older adults with mild Alzheimer's-type dementia watched movies of everyday activities and completed memory tests on the activities. Structural MRI was used to measure brain volume. Medial temporal but not prefrontal volume strongly predicted subsequent memory. Everyday memory depends on segmenting activity into discrete events during perception, and medial temporal volume partially accounted for the relationship between performance on the memory tests and performance on an event-segmentation task. The everyday-memory measures used in this study involve retrieval of episodic and semantic information as well as working memory updating. Thus, the current findings suggest that during perception, the medial temporal lobes support the construction of event representations that determine subsequent memory.
perception; memory; cognitive neuroscience; aging
Optimistic expectancies affect many psychosocial outcomes and may also predict immune system changes and health, but the nature and mechanisms of any such physiological effects have not been identified. The present study related law-school expectancies to cell-mediated immunity (CMI), examining the within- and between-person components of this relationship and affective mediators. First-year law students (N = 124) completed questionnaire measures of expectancies and affect and received delayed-type hypersensitivity skin tests at five time points. A positive relationship between optimistic expectancies and CMI occurred, in which that changes in optimism correlated with changes in CMI. Likewise, changes in optimism predicted changes in positive and, to a lesser degree, negative affect, but the relationship between optimism and immunity was partially accounted for only by positive affect. This dynamic relationship between expectancies and immunity has positive implications for psychological interventions to improve health, particularly those that increase positive affect.
optimism; expectancy; affect; cell-mediated immunity
Language and math are intertwined during children’s learning of arithmetic concepts, but the importance of language in adult arithmetic processing is less clear. To determine whether early learning plays a critical role in the math-language connection in adults, we tested retrieval of simple multiplication in adult bilinguals who learned arithmetic in only one language. We measured electrophysiological and behavioral responses during correctness judgments for problems presented as digits or as number words in Spanish or English. Problems presented in the language in which participants learned arithmetic elicited larger, more graded, and qualitatively different brain responses than did problems presented in participants’ other language, and these responses more closely resembled responses for digits, even when participants’ other language was more dominant. These findings suggest that the memory networks for simple multiplication are established when arithmetic concepts are first learned and are independent of language dominance in adulthood.
bilingualism; mathematical ability; evoked potentials; language; cognitive neuroscience
Communication is aided greatly when speakers and listeners take advantage of mutually shared knowledge (i.e., common ground). How such information is represented in memory is not well known. Using a neuropsychological-psycholinguistic approach to real-time language understanding, we investigated the ability to form and use common ground during conversation in memory-impaired participants with hippocampal amnesia. Analyses of amnesics’ eye fixations as they interpreted their partner's utterances about a set of objects demonstrated successful use of common ground when the amnesics had immediate access to common-ground information, but dramatic failures when they did not. These findings indicate a clear role for declarative memory in maintenance of common-ground representations. Even when amnesics were successful, however, the eye movement record revealed subtle deficits in resolving potential ambiguity among competing intended referents; this finding suggests that declarative memory may be critical to more basic aspects of the on-line resolution of linguistic ambiguity.
language; memory; cognitive neuroscience
In two experiments, we examined whether observers’ eye movements distinguish studied faces from highly similar novel faces. Participants’ eye movements were monitored while they viewed three-face displays. Target-present displays contained a studied face and two morphed faces that were visually similar to it; target-absent displays contained three morphed faces that were visually similar to a studied, but not tested, face. On each trial in a test session, participants were instructed to choose the studied face if it was present or a random face if it was not and then to indicate whether the chosen face was studied. Whereas manipulating visual similarity in target-absent displays influenced the rate of false endorsements of nonstudied items as studied, eye movements proved impervious to this manipulation. Studied faces were viewed disproportionately from 1,000 to 2,000 ms after display onset and from 1,000 to 500 ms before explicit identification. Early viewing also distinguished studied faces from faces incorrectly endorsed as studied. Our findings show that eye movements provide a relatively pure index of past experience that is uninfluenced by explicit response strategies, and suggest that eye movement measures may be of practical use in applied settings.
eye movements; false memory; episodic memory; visual memory