When even arbitrary order becomes important: developments in reliable temporal sequencing of arbitrarily ordered events.

By late in the first year of life, children show temporally ordered recall of event sequences, the orders of which are constrained by enabling relations; they do not reliably recall arbitrarily ordered events. Using elicited imitation, in two experiments, we examined age- and experience-related changes in young children's recall of events, the orders of which are arbitrary. The changes were found to have implications for the efficacy of verbal reminding and to be related to developments in language. Specifically, on the basis of a single experience, 16-month-olds did not accurately recall arbitrarily ordered event sequences either immediately or after a two-week delay (Experiment 1); 22-month-olds recalled the events immediately, but not after the delay; by 28 months, children recalled the events even after the delay (Experiment 2A). This development was accompanied by changes in the ability to benefit from verbal reminders: 28-month-olds' recall was facilitated by provision of verbal reminders, whereas that of the younger children was not. Moreover, age-related changes in accurate reproduction of lengthy arbitrarily ordered event sequences were found to be related to developments in language (Experiment 2B). Critically, the limitations on 1-year-olds' performance that are overcome with age are not absolute: After three experiences, 16-month-olds accurately recalled the events after a two-week delay; their recall was facilitated by verbal reminders (Experiment 1). The implications of these findings are discussed.

Adrenocortical responses to the strange situation in infants with disorganized/disoriented attachment relationships.

Salivary cortisol levels were assessed in 19-month-old infants following the Ainsworth Strange Situation procedure. 38 infants participating in Project STEEP at the University of Minnesota served as subjects. Project STEEP is a longitudinal intervention program designed to promote healthy parent-child relationships and to prevent emotional problems among children born to mothers who are at high risk for parenting problems. Following the Strange Situation, saliva samples were collected and assayed for cortisol, a steroid hormone frequently examined in studies of stress. Behavior during the Strange Situation was coded by trained coders, and attachment classifications were determined for each infant. Cortisol concentrations did not differ between the 6 Avoidant/Resistant (A/C) and 17 Securely Attached (B) toddlers. Toddlers (n = 11) who were classified as having Disorganized/Disoriented (Type D) attachments exhibited higher cortisol concentrations than toddlers in the traditional (ABC) classifications. Results of this study were consistent with a model of stress reactivity that conceptualizes the organization of coping behaviors as a factor that mediates physiological stress responses.

Effects of experience and reminding on long-term recall in infancy: remembering not to forget.

We examined whether some of the factors that facilitate recall in older children also extend to 1- to 2-years-olds. Using elicited imitation we assessed the efficacy of verbal (Experiment 1), and verbal plus nonverbal (Experiment 2) reminding on 15-month-olds' recall after a 1-week delay. Reminding ameliorated forgetting: Performance at delayed and immediate recall was equivalent. The addition of nonverbal information did not enhance recall above verbal information alone. In Experiment 3 we investigated the influence of verbal reminding, repeated experience, and mode of experience (i.e., imitate vs watch only) on recall after 1 month. The effects of reminding depended on event type: Reminding facilitated recall of events with enabling relations, but not of events lacking them. Repeated experience and the opportunity to imitate facilitated recall; children who watched events only once nevertheless recalled them. Results suggest that the strength of organization of an event representation, rather than retention interval, is a major determinant of remembering during the second year of life.

After 8 months have passed: long-term recall of events by 1- to 2-year-old children.

The time course of development of the ability to remember specific past events is a matter of considerable curiosity and debate. Traditional and contemporary theories alike suggest that infants are unable to consolidate and stabilise event knowledge for recall after a long time period. In two experiments, we used elicited imitation, a nonverbal analogue to cued verbal recall, to test 21-, 24-, and 29-month-old children's recall of events they had experienced eight months previously. At the time of original exposure some of the events were novel, whereas others depicted activities familiar to 1-year-olds. At the eight-month retention test, performance of the experienced children was compared to that of matched naive controls. In both experiments the experienced children produced a greater number of the novel events; there were no differences between the groups on the familiar events. The results demonstrate long-term recall of specific past events by 1- to 2-year-olds. They thus challenge the suggestion that the absence of memories from infancy and early childhood is attributable to the inability to form memories that are enduring and accessible over time.

Increasing steps in recall of events: factors facilitating immediate and long-term memory in 13.5- and 16.5-month-old children.

Children late in the second year of life show patterns of event recall similar to those of older children: (a) well-ordered immediate and delayed recall, and (b) facilitation of recall by familiarity and by enabling relations. We used elicited imitation to test whether the patterns extend to children early in the second year. In Experiment 1, 13.5- and 16.5-month-olds accurately recalled familiar and novel 2-act sequences immediately and after a 1-week delay. For 16.5-month-olds, recall was facilitated by familiarity and by enabling relations; for 13.5-month-olds, only enabling relations facilitated recall. In Experiment 2, verbal cues were used to test immediate and 1-week delayed recall of 3-act sequences. For both ages, recall was facilitated by familiarity and by enabling relations. Experiment 3 verified that the verbal information served to cue recall of previously experienced events, not to "suggest" sequences that could be performed. Together the results demonstrate that children as young as 13 months can recall specific events after a delay. They also suggest development in sensitivity to factors that facilitate recall.

First time experiences in infancy: when they appear to be pleasant, do they activate the adrenocortical stress response?

The effect of a positive first-time experience on adrenocortical activity was examined in 48 6- to 13-month-old infants who took part in two sessions of a YMCA-like mother-infant swim class. Experience was manipulated by comparing Novice swimmers with infants who previously had taken a swim class, and by examining responses to first versus second class session. In addition, the effects of temperamental fear of novelty were examined by maternal report prior to the first session. Preswim and Postswim cortisol levels were compared to measures obtained at the same time of day in two comparison groups, one tested at home and one tested in a playroom at the University. The results yielded no evidence of an adrenocortical stress response (elevated cortisol) to the swim sessions for either the Novice or Experienced swimmers. Infant temperamental fearfulness predicted behavioral but not adrenocortical responses during swimming. Postswim cortisol levels were significantly lower than posttest levels in the two baseline comparison groups, and lower postswim cortisol levels were associated with less negative and more positive emotional behavior and engagement of the swimming experience. These results are consistent with the hypothesis that emotions serve as a major pathway influencing adrenocortical activity, and provide no support for the uncertainty hypothesis of adrenocortical activation.

The stressfulness of separation among nine-month-old infants: effects of social context variables and infant temperament.

This manuscript reports on the results of 2 experiments dealing with behavioral and adrenocortical responses to separation among 9-month-old human infants. In both experiments the social context of separation was manipulated. The results of Experiment 1 yielded evidence of a statistically significant adrenocortical response to 30 min of separation under conditions in which the substitute caregiver responded sensitivity to infant distress, but was busy and relatively noninteractive when babies were not distressed during the separation period. Altering the behavior of the substitute caregiver such that she was warm, responsive, and interactive throughout the separation produced a significant reduction in adrenocortical activity and in negative affect. In fact, these measures were not significantly different than those obtained when the mother and infant remained together in the playroom (No Separation). In Experiment 2, the effects of group versus singleton care were examined using the less stressful mode of substitute caregiving as described above. No significant condition differences in behavioral distress or cortisol were found. Furthermore, neither condition elicited a significant increase in cortisol over basal levels. Finally, these data provide evidence that maternal reports of infant Distress to Limits temperament, using Rothbart's Infant Behavior Questionnaire, predict adrenocortical responses to separation, while reports of Fear of Novelty do not.

Cortisol and behavioral responses to repeated stressors in the human newborn.

This manuscript reports on the effects of stressors repeated at a 24-hr interval on three samples of human newborns. In Study 1, newborns meeting criteria for obstetric and perinatal optimality experienced either 2 mock Discharge Exams, viewed as a type of handling stressor, or 2 Heelstick Blood Draws, viewed as a type of nocioceptive stressor. As in a previous study, newborns meeting optimality criteria showed habituation of the adrenocortical response to the repeated Discharge Exam. The adrenocortical response to the repeated Heelstick tended to increase or sensitize. In Studies 2 and 3, samples of newborns with more nonoptimal obstetric complication scale scores were examined. These newborns failed to show habituation of the adrenocortical response to the Discharge Exam, but responded like "Optimal" newborns to the repeated Heelstick. The applicability to these data of the Groves and Thompson (1970) Dual-Process Model of Habituation is discussed. The results also provided evidence of stability in behavioral distress independent of stability in adrenocortical activity. The implications of these data for studies using cortisol as an index of the physiological basis of early temperament are considered.

The effects of morning naps, car trips, and maternal separation on adrenocortical activity in human infants.

3 studies of adrenocortical activity in healthy 9-month-old infants were conducted to examine unanticipated results obtained in previous research. In the first study, morning naps were examined and found to be associated with significant decreases in salivary cortisol. These decreases were followed by a significant return to prenap cortisol concentrations. In the second study, riding for 40 min in the car was also shown to significantly lower salivary cortisol concentrations. This effect was obtained both for infants who did and who did not sleep during the car trip. In the third study, the effect of 30 min of maternal separation in the laboratory on salivary cortisol was compared to the effect of 30 min of play with mother present. Separation resulted in significantly higher salivary cortisol concentrations as compared to play with mother present. In general, correlations between cortisol and behavior were found to be nonsignificant under conditions that did not produce stress elevations in cortisol, while less positive, more distressed behaviour was significantly correlated with cortisol under separation or stress conditions.