Effects of fluid delivery on the sucking response of the human newborn

Two experiments were conducted with human newborns to compare sucking behavior under nutritive and nonnutritive sucking conditions using several fixed-ratio schedules of reinforcement. Results showed that: (1) nutritive sucking produces higher over-all sucking rates but lower within-burst rates, (2) burst lengths are longer during nutritive than nonnutritive sucking, (3) fewer bursts per unit time occur during nutritive sucking, (4) fluid termination following nutritive sucking produces a sharp response decrement, suggestive of a negative contrast effect when compared with sucking rates under continuous no-fluid sucking. Response diminution occurs in the first 2–3 min of sucking under all conditions, reflecting the necessity of control comparisons in studies documenting sucking change under changing stimulus or reinforcement conditions.     

Reinforcement from the sucking environment and subsequent modification of sucking behavior in the human neonate

The reinforcing aspects of sucking behavior in 36 human newborns was examined in a limited instrumental conditioning paradigm where sucking was both operant and reinforcer. During training, response density (rate based on sucking opportunity time) and latency were measures of two components of nonnutritive sucking, contingent negative pressure suction, and incidental jaw movement. The strategy for determining the reinforcing aspects of sucking involved comparisons of three types of sucking stimuli as reinforcers. The nature of modified operant sucking was investigated during extinction by examining number of sucks per burst, number of bursts emitted, and interburst interval time. The feedback from sucking which acted as reinforcement was concluded to be response density. Sucking was modified by changes in pausing behavior, including response latency and pauses between bursts of sucks. The number of sucks per burst also showed a significant change under certain conditioning arrangements.     

A further analysis of the effect of satiation on the sucking response in puppies

The Psychological Record - A total of 84 tests were made on puppies to further examine the influence of stomach injected food on the sucking reflex. Sucking followed injection of milk in every...     

A mental number line in human newborns

Humans represent numbers on a mental number line with smaller numbers on the left and larger numbers on the right side. A left‐to‐right oriented spatial–numerical association, (SNA), has been demonstrated in animals and infants. However, the possibility that SNA is learnt by early exposure to caregivers’ directional biases is still open. We conducted two experiments: in Experiment 1, we tested whether SNA is present at birth and in Experiment 2, we studied whether it depends on the relative rather than the absolute magnitude of numerousness. Fifty‐five‐hour‐old newborns, once habituated to a number (12), spontaneously associated a smaller number (4) with the left and a larger number (36) with the right side (Experiment 1). SNA in neonates is not absolute but relative. The same number (12) was associated with the left side rather than the right side whenever the previously experienced number was larger (36) rather than smaller (4) (Experiment 2). Control on continuous physical variables showed that the effect is specific of discrete magnitudes. These results constitute strong evidence that in our species SNA originates from pre‐linguistic and biological precursors in the brain.     

Effects of gastric loading on the sucking response and voluntary milk intake in neonatal piglets.

The effects of loading the stomach of piglets with 100 ml of milk after 6 hr of fasting and immediately before allowing them access to the dam were studied. Piglets gained less weight and rested more often on preloaded days. This suggests that gastric receptors exist and signal distension of the stomach. Monitoring sucking responses to a rubber teat revealed that although preloading the stomach substantially reduced voluntary milk intake during the initial 10-min. period of the test, the vigorous oral activity continued largely unabated. Isotonic saline suppressed the voluntary milk intake of the piglets for a shorter period than milk or isotonic glucose solution.