Perceptual-motor sequence learning of general regularities and specific sequences.

Participants viewed digit strings and typed them on a computer keyboard. When they used the same key configuration across training and test, they typed test strings that adhered to the same sequence rule as training strings faster than test strings that adhered to the opposite rule (general-regularity [GR] learning), and they typed test strings that were processed repeatedly during training faster than test strings that were not (specific-sequence [SS] learning). However, when they used different key configurations at training and at test, GR learning, but not SS learning, was observed. Conversely, when they did not type but spoke the strings aloud during training, SS learning, but not GR learning, was observed. Results suggest that in addition to declarative memory for specific sequences, relatively independent subsystems underlie procedural learning of perceptual-motor sequence components (producing GR effects) and sequence wholes (producing SS effects).     

Reevaluating evaluative conditioning: a nonassociative explanation of conditioning effects in the visual evaluative conditioning paradigm.

In 2 studies, the authors investigated whether evaluative conditioning (EC) is an associative phenomenon. Experiment 1 compared a standard EC paradigm with nonpaired and no-treatment control conditions. EC effects were obtained only when the conditioned stimulus (CS) and unconditioned stimulus (UCS) were rated as perceptually similar. However, similar EC effects were obtained in both control groups. An earlier failure to obtain EC effects was reanalyzed in Experiment 2. Conditioning-like effects were found when comparing a CS with the most perceptually similar UCSs used in the procedure but not when analyzing a CS rating with respect to the UCS with which it was paired during conditioning. The implications are that EC effects found in many studies are not due to associative learning and that the special characteristics of EC (conditioning without awareness and resistance to extinction) are probably nonassociative artifacts of the EC paradigm.     

Changes in imitative behavior during early infancy

Changes in imitative behavior and attentiveness were observed in 40 infants when they were 2 to 6 months of age. The facial expressions happy, sad, and surprised were modeled in a trials-to-criterion procedure, and the infants' looking time and mouth movements were recorded by an observer who was unaware of the face being modeled. In addition, the observer recorded her guess as to the expression being modeled by the corresponding expression on the infant's face and rated the infant's expressivity. The results suggested that looking time, correspondence between the mouth expression of the infant and the mouth expression modeled, accuracy of the observer's guess, and expressivity ratings decreased from 2 to 3 and 4 to 6 months. Although matching of mouth movements with the modeled mouth movements and accuracy of guesses were greater than chance over the 2 to 6 month-period, the decreases in these measures suggest that imitative behavior declined across early infancy. The decrease in looking time suggests that imitative behavior and attentiveness may be related and highlights the limitation of this paradigm for assessing the development of imitation during early infancy.     

Prenatal cortisol, prematurity and low birthweight

Three hundred depressed pregnant women were recruited at approximately 20 weeks gestation. They were then divided by a median split into high and low urinary cortisol level groups. The high cortisol group had higher CES-D depression scores and higher inhibition (BIS) scores prenatally. Their fetuses had smaller head circumference, abdominal circumference, biparietal diameter and fetal weight. The high cortisol group neonates were shorter gestational age and lower birthweight and they had lower Brazelton habituation and higher Brazelton reflex scores. Discriminant function analyses suggested that cortisol levels more accurately classified short gestation and low birthweight groups than CES-D depression scores.     

Happy faces are habituated more slowly by infants of depressed mothers

Three-month-old infants of depressed (n=16) and non-depressed mothers (n=16) were habituated to video clips of a female model reciting phrases while posing happy or sad facial/vocal expressions and dishabituated to the alternate expressions. Overall, infants of depressed mothers took longer to habituate the video clips compared to infants of non-depressed mothers, and those assigned to habituate the sad video clips displayed a novelty response or dishabituated to the happy expressions. These findings suggest that 3-month-old infants of depressed mothers discriminate sad from happy expressions, however, they do not appear to perceive sad expressions as novel.     

Newborns of depressed mothers who received moderate versus light pressure massage during pregnancy

Sixty-four neonates (M age=6.8 days) of depressed mothers who received moderate pressure massage versus light pressure massage therapy during pregnancy (month 5 through month 8) were compared on their behaviors during 15-min observations and on their performance on the Brazelton Neonatal Behavior Assessment Scale. The group of neonates whose mothers received moderate pressure massage spent a greater percent of the observation time smiling and vocalizing, and they received better scores on the orientation, motor, excitability, and depression clusters of the Brazelton scale.     

Greater arousal and less attentiveness to face/voice stimuli by neonates of depressed mothers on the Brazelton Neonatal Behavioral Assessment Scale

Neonates born to depressed (n = 44) versus non-depressed (n = 43) mothers were compared on individual items of the Brazelton Neonatal Behavioral Assessment Scale (NBAS). The neonates of depressed mothers received lower scores on orienting to the live face/voice stimulus and on the alertness items, suggesting they were less attentive. They also scored less optimally on the cuddliness and hand-to-mouth activity items, suggesting they were more aroused. These data lend support to the model that infants of depressed mothers are more aroused and less attentive.     

Prenatal paternal depression

Prenatal depressive symptoms, anxiety, anger and daily hassles were investigated in 156 depressed and non-depressed pregnant women and their depressed and non-depressed partners (fathers-to-be). Depressed versus non-depressed fathers had higher depression, anxiety and daily hassles scores. Although the pregnant women in general had lower anxiety, anger and daily hassles scores than the men, the scores on the measures for depressed fathers and depressed mothers did not differ. Paternal depression appeared to have less effect than maternal depression on their partners’ scores. However, the similarity between the scores of depressed mothers and depressed fathers highlights the importance of screening for depression in fathers-to-be as well as mothers-to-be during pregnancy.     

A TEST OF THE FORMAL AND MODERN THEORIES OF MATCHING

Pigeons' choosing between fixed-interval and random-interval schedules of reinforcement was investigated in three experiments using a discrete-trial procedure. In all three experiments, the random-interval schedule was generated by sampling a probability distribution at an interval (and in multiples of the interval) equal to that of the fixed-interval schedule. Thus the programmed delays to reinforcement on the random alternative were never shorter and were often longer than the fixed interval. Despite this feature, the fixed schedule was not strongly preferred. Increases in the probability used to generate the random interval resulted in decreased preferences for the fixed schedule. In addition, the number of consecutive choices on the preferred alternative varied directly with preference, whereas the consecutive number of choices on the nonpreferred alternative was fairly constant. The probability of choosing the random alternative was unaffected by the immediately prior interval encountered on that schedule, even when it was very long relative to the average value. The results loosely support conceptions of a "preference for variability" from foraging theory and the "utility of behavioral variability" from human decision-making literatures.