Effects of Delayed Reinforcement on Infant Vocalization Rate

Abstract

Three previous studies have failed to demonstrate conditioning in infants using a 3-s delay of reinforcement. The effects of a delayed reinforcement schedule on vocalization rates therefore were explored in a single-subject repeated-reversal experimental design for 3 4-to 6-month-old normally developing infants. Each infant received delayed social reinforcement from his or her parent for vocalizing. The comparison condition was a schedule of differential reinforcement of behavior other than vocalizations to control for elicitation by social stimulation. An operant level of infant vocalizations was the initial condition, after which the differential reinforcement schedule was implemented in an across-subjects multiple baseline design. Infants' vocalization rates increased above levels measured during differential reinforcement following onset of the delayed reinforcement condition. Also, vocalization rates decreased during differential reinforcement compared to operant levels. The successful use of delayed reinforcement schedules with infants in this study, as opposed to others, is discussed in terms of procedural differences among them.Key words: delayed reinforcement, vocalizations, differential reinforcement of other behavior, social reinforcement, methodology, infants Dating back to Plato and Aristotle, the notion of temporal contiguity has been invoked as a relevant feature in stimulus association (Leahey, 1980). When the temporal interval between a response and a consequence is lengthened, the subsequent association may be weaker than associations formed with more contiguous events. The association between delayed reinforcement and responding has been investigated in several species, including rats (Grice, 1948;Wolfe, 1934), pigeons (Dews, 1960;Ferster, 1953;Gleeson & Lattal, 1987;Sizemore & Lattal, 1977;Williams, 1976), and monkeys (Ferster & Hammer, 1965), in addition to human infants (Millar, 1972;Millar & Watson, 1979;Ramey & Ourth, 1971) and children (R. Baer, Williams, Osnes, & Stokes, 1984;Fowler & Baer, 1981

A Parametric Variation of Delayed Reinforcement in Infants

“…In both experiments, delayed reinforcement resulted in a systematic increase in the vocalization rates of infants. These results are consistent with those of Reeve et al (1992), but not with some of the earlier literature on infants (Millar & Watson, 1979;Ramey & Ourth, 1971). As in the Reeve et al study, each infant in the current experiments was presented with each experimental condition over many daily 12-min sessions, and conditioning with delayed reinforcement was obtained for delays of 3 s and longer.…”

“…Dews (1960) demonstrated an increase in responding during delayed reinforcement, and Pierce et al (1972) showed no difference between DRO and delayed reinforcement. In studies with infants, DRO was used as a control condition by Reeve et al (1992), and conditioning was demonstrated with delayed reinforcement. Although a programmed DRO schedule should produce little adventitious reinforcement of the target response, analysis of reinforcement rates may nevertheless clarify the reason for the contradictory data of Pierce et al (1972) and other researchers using DRO schedules.…”

“…An additional consideration in experimental design using delayed reinforcement is the delay procedure itself. In contrast to the early developmental literature, conditioning with signaled delays of 3 s in infants has been demonstrated in one recent study (Reeve et al, 1992). This experiment consisted of a repeated-reversal experimental design comparing delayed reinforcement with a differentialreinforcement-of-other-behavior (DRO) schedule.…”

“…Skill deficits indexed by the age of the infant or the length of the delay may be mitigating factors (Millar, 1972). Indeed, in only one study has conditioning been demonstrated in infants as young as 4 months with delays of reinforcement as long as 3 s (Reeve, Reeve, Brown, Brown, & Poulson, 1992). It would not be surprising to find that additional presentation of the contingency might be important to the acquisition of responding under delayed reinforcement.…”

Designing Interventions That Include Delayed Reinforcement: Implications of Recent Laboratory Research

“…Delayed reinforcement can be arranged to establish and maintain responding in the absence of shaping or other training (e.g., Lattal & Williams, 1997). This phenomenon has been demonstrated across several species, including rats and pigeons (Lattal & Gleeson, 1990;Wilkenfield, Nickel, Blakely, & Poling, 1992), Siamese fighting fish (Lattal & Metzger, 1994), and human infants (Reeve, Reeve, Brown, Brown, & Poulson, 1992). The findings of such studies consistently demonstrate that unsignaled delayed reinforcement produces low but persistent rates of responding (Critchfield & Lattal, 1993;Lattal & Gleeson, 1990;Wilkenfield et al, 1992).…”