Knowledge that Transforms

With datafrom the NICHD Study of Early Child Care, we used structural equation modeling to test paths from structural indicators of child-care quality, specifically caregiver training and child-staff ratio, through a process indicator to child outcomes. There were three main findings: (a) Quality of maternal caregiving was the strongest predictor of cognitive competence, as well as caregivers' ratings of social competence; (b) quality of nonmaternal caregiving was associated with cognitive competence and caregivers' ratings of social competence; and (c) there was a mediated path from both caregiver training and child-staff ratio through quality of nonmaternal caregiving to cognitive competence, as well as to caregivers' ratings of social competence, that was not accounted for entirely by family variables. These findings provide empirical support for policies that improve state regulations for caregiver training and child-staff ratios.

Auditory sequences of tones were used to examine a form of stimulus-driven attending that involves temporal expectancies and is influenced by stimulus rhythm. Three experiments examined the influence of sequence timing on comparative pitch judgments of two tones (standard, comparison) separated by interpolated pitches. In two of the experiments, interpolated tones were regularly timed, with onset times of comparison tones varied relative to this rhythm. Listeners were most accurate judging the pitch of rhythmically expected tones and least accurate with very unexpected ones. This effect persisted over time, but disappeared when the rhythm of interpolated tones was either missing or irregular.

By the age of 3, children easily learn to name new objects, extending new names for unfamiliar objects by similarity in shape. Two experiments tested the proposal that experience in learning object names tunes children's attention to the properties relevant for naming--in the present case, to the property of shape--and thus facilitates the learning of more object names. In Experiment 1, a 9-week longitudinal study, 17-month-old children who repeatedly played with and heard names for members of unfamiliar object categories well organized by shapeformed the generalization that only objects with ith similar shapes have the same name. Trained children also showed a dramatic increase in acquisition of new object names outside of the laboratory during the course of the study. Experiment 2 replicated these findings and showed that they depended on children's learning both a coherent category structure and object names. Thus, children who learn specific names for specific things in categories with a common organizing property--in this case, shape--also learn to attend to just the right property--in this case, shape--for learning more object names.

A new choice task was used to explore infants' spontaneous representations of more and less. Ten- and 12-month-old infants saw crackers placed sequentially into two containers, then were allowed to crawl and obtain the crackers from the container they chose. Infants chose the larger quantity with comparisons of 1 versus 2 and 2 versus 3, but failed with comparisons of 3 versus 4, 2 versus 4, and 3 versus 6. Success with visible arrays ruled out a motivational explanation for failure in the occluded 3-versus-6 condition. Control tasks ruled out the possibility that presentation duration guided choice, and showed that presentation complexity was not responsible for the failure with larger numbers. When crackers were different sizes, total surface area or volume determined choice. The infants 'pattern of success and failure supports the hypothesis that they relied on object-file representations, comparing mental models via total volume or surface area rather than via one-to-one correspondence between objectfiles.

Two experiments investigated learning of nonadjacent dependencies by adults and 18-month-olds. Each learner was exposed to three-element strings (e.g., pel-kicey-jic) produced by one of two artificial languages. Both languages contained the same adjacent dependencies, so learners could distinguish the languages only by acquiring dependencies between the first and third elements (the nonadjacent dependencies). The size of the pool from which the middle elements were drawn was systematically varied to investigate whether increasing variability (in theform of decreasing predictability between adjacent elements) would lead to better detection of nonadjacent dependencies. Infants and adults acquired nonadjacent dependencies only when adjacent dependencies were least predictable. The results point to conditions that might lead learners to focus on nonadjacent versus adjacent dependencies and are importantfor suggesting how learning might be dynamically guided by statistical structure.

How are people able to think about things they have never seen or touched? We demonstrate that abstract knowledge can be built analogically from more experience-based knowledge. People's understanding of the abstract domain of time, for example, is so intimately dependent on the more experience-based domain of space that when people make an air journey or wait in a lunch line, they also unwittingly (and dramatically) change their thinking about time. Further, our results suggest that it is not sensorimotor spatial experience per se that influences people's thinking about time, but rather people's representations of and thinking about their spatial experience.

We examined the prediction that people activate perceptual symbols during language comprehension. Subjects read sentences describing an animal or object in a certain location. The shape of the object or animal changed as a function of its location (e.g., eagle in the sky, eagle in a nest). However, this change was only implied by the sentences. After reading a sentence, subjects were presented with a line drawing of the object in question. They judged whether the object had been mentioned in the sentence (Experiment 1) or simply named the object (Experiment 2). In both cases, responses were faster when the pictured object's shape matched the shape implied by the sentence than when there was a mismatch. These results support the hypothesis that perceptual symbols are routinely activated in language comprehension.

Functional decay theory proposes that decay and interference, historically viewed as competing accounts of forgetting, are instead functionally related. The theory posits that (a) when an attribute must be updated frequently in memory, its current value decays to prevent interference with later values, and (b) the decay rate adapts to the rate of memory updates. Behavioral predictions of the theory were tested in a task-switching paradigm in which memory for the current task had to be updated every few seconds, hundreds of times. Reaction times and error rates both increased gradually between updates, reflecting decay of memory for the current task. This performance decline was slower when updates were less frequent, reflecting a decrease in the decay rate following a decrease in the update rate. A candidate mechanism for controlled decay is proposed, the data are reconciled with practice effects, and implications for models of executive control are discussed.

Loneliness predicts morbidity and mortality from broad-based causes, but the reasons for this effect remain unclear. Few differences in traditional health behaviors (e.g., smoking, exercise, nutrition) have been found to differentiate lonely and nonlonely individuals. We present evidence that a prototypic restorative behavior--sleep--does make such a differentiation, not through differences in time in bed or in sleep duration, but through differences in efficacy: In the study we report here, lonely individuals evinced poorer sleep efficiency and more time awake after sleep onset than nonlonely individuals. These results, which were observed in controlled laboratory conditions and were found to generalize to the home, suggest that lonely individuals may be less resilient than nonlonely individuals in part because they sleep more poorly. These results also raise the possibility that social factors such as loneliness not only may influence the selection of health behaviors but also may modulate the salubrity of restorative behaviors.

A sample of 222 undergraduates was screened for high happiness using multiple confirming assessment filters. We compared the upper 10% of consistently very happy people with average and very unhappy people. The very happy people were highly social, and had stronger romantic and other social relationships than less happy groups. They were more extraverted, more agreeable, and less neurotic, and scored lower on several psychopathology scales of the Minnesota Multiphasic Personality Inventory. Compared with the less happy groups, the happiest respondents did not exercise significantly more, participate in religious activities significantly more, or experience more objectively defined good events. No variable was sufficient for happiness, but good social relations were necessary. Members of the happiest group experienced positive, but not ecstatic, feelings most of the time, and they reported occasional negative moods. This suggests that very happy people do have a functioning emotion system that can react appropriately to life events.