Evidence for a transitional period for development of persistence in infant rats.

Abstract

Four experiments point to the existence of a transitional period in neonatal rats for the learning of persistence. Partial reinforcement training with suckling on an anesthetized dam as reward induced greater persistence in extinction of the approach response than did continuous reinforcement in rat pups 14 days old but not in 11-day-old pups. Other aspects of this period of development are discussed.The partial reinforcement extinction effect (FREE) describes the relative persistence-increased resistance to extinction-that results from partial or intermittent reinforcement relative to the continuous reinforcement of an instrumental response. Research in our laboratory has demonstrated the occurrence of the FREE in preweanling rat pups (as young as 17-18 days of age) with dry food as reward and the retention of this learned persistence over a 50-day period ). In more recent experiments we have shown that appetitive instrumental learning and extinction is possible in previsual and preaudile (10-to 11-day-old) rat pups (Amsel, Burdette, & Letz, 1976;Amsel, Letz, & Burdette, 1977). There is, however, no evidence of a FREE in 11-day-old rat pups with nonnutritive suckling as reward (Amsel, Letz, & Burdette, 1977, Experiment 2).Consequently, in the present series of experiments, we attempted to identify a transitional period for the manifestation of the FREE. In Experiment 1, we developed a spaced-trial procedure and investigated the effect of the type of suckling experience on acquisition and extinction of an approach response of 11-and 14-day-old rat pups, hi Experiment 2, schedule of reward and type of suckling experience were manipulated in

Short‐ and long‐term effects of various milk‐delivery contingencies on sucking and nipple attachment in rat pups

“…The results of the previous experiments, as well as those of others (Brake, 1981;Brake et al, 1982;Letz et al, 1978), demonstrate that rat pups as young as 11 days of age perceive milk delivery as a salient event and are capable of discriminating suckling associated with milk delivery from nonnutritive suckling. Rat pups apparently become even more responsive to the nutritive contingencies associated with feeding between 15 and 25 days of age (Kenny et al, 1979;Williams, Hall, & Rosenblatt, 1980), which is the beginning of the weaning period.…”

“…Pups given experience with continuous milk delivery from 14 to 18 days of age also spent significantly more time attached to the nipple at 19 days of age than did pups in control groups. It was concluded that experience with different milk delivery schedules can affect subsequent sucking and nipple attachment behavior.Several investigators have demonstrated that 2-week-old rats traverse runways and mazes more efficiently when reinforcement consists of sucking a nipple which provides milk rather than sucking a nipple which does not (Letz, Burdette, Gregg, Kittrell, & Amsel, 1978;Kenny, Stolhoff, Bruno, & Blass, 1979). We are now finding that the pup's behavior while on the nipple is also affected by milk delivery.…”

“…Several investigators have demonstrated that 2-week-old rats traverse runways and mazes more efficiently when reinforcement consists of sucking a nipple which provides milk rather than sucking a nipple which does not (Letz, Burdette, Gregg, Kittrell, & Amsel, 1978;Kenny, Stolhoff, Bruno, & Blass, 1979). We are now finding that the pup's behavior while on the nipple is also affected by milk delivery.…”

Dissociation of patterned alternation learning and the partial reinforcement extinction effect in preweanling rats

“…Beyond this general trend, however, we have found that the PREE appears much earlier in ontogeny than do other paradoxical effects. The PREE first appears at 12-14 days (Chen & Amsel, 1980;Letz, Burdette, Gregg, Kittrell, & Amsel, 1978), whereas the MREE fails to appears clearly until about 21 days (Burdette, Brake, Chen, & Amsel, 1976;Chen, Gross, & Amsel, 1981;; SNC first appears at 25-26 days (Chen et al, 1981;; and there is no evidence of the OEEprior to 25-26 days . The sequence of appearance of these extinction effects remains to be explained by theories that attribute these effects to a common set of learning mechanisms.…”

Endnotes

“…The suggestion by Bitterman is that the early appearance of the PREE may depend on training with relatively massed trials. He might be right, but we do have experiments on the PREE in 14-day-old rats in which the intertrial interval (lTI) is 10-12 min (Letz, Burdette, Gregg, Kittrell, & Amsel, 1978). Bitterman's statement that massed-trial SNC can be accounted for in terms of primary frustration (R F) alone is puzzling: in massed trials, primary frustration produces FE-like effects, not SNC.…”