Reward sequence and reinforcement level as determinants of S− behavior in differential conditioning

Abstract

In two differential conditioning experiments, groups of 10 rats each differed with respect to average reward and schedule of reward received in S+. Nonreward (N) occurred on all Strials. In both experiments, extinction of responding to S-(resistance to discrimination) was extensively regulated by reward sequence and was largely independent of average reward. In Experiment I, resistance to discrimination was a function of transitions from N to rewarded (R) trials (N-R transitions). In Experiment 2, resistance to discrimination was increased by large reward on the R trial of N-R transitions and decreased by large reward on the R trial of R-N transitions. These schedule effects on resistance to discrimination parallel the effects of comparable schedules on resistance to extinction following partial reinforcement. The results are discussed in terms of sequential theory, reinforcement level theory, and their implications for various schedule manipulations that have previously shown S-behavior to be inversely related to average reward in S+.Two factors have been shown to be particularly important in regulating behavior to the negative (S-) stimulus during differential conditioning, trial sequence (Capaldi, Berg, & Morris, 1975;Haggbloom, 1978Haggbloom, , 1979Haggbloom, , 1980McHose & Blackwell, 1975) and the difference between the average incentive associated with the two discriminanda (McHose, 1970).The incentive averaging view is illustrated by an experiment reported by McHose, Maxwell, and McHewitt (1971, Experiment 4). In that experiment, all groups received nonreward (N) in S-; one group received eight and another two 45-mg food pellets on all S+ trials; and a third group, crucial to the incentive averaging view, received a 50% partial reinforcement (PRF) schedule in S+, obtaining 16 pellets on rewarded (R) trials. Where the numerals indicate S+ and S-reward, these groups can be identified, respectively, as Groups 8-0, 2-0, and 16/0-0.Using formulas suggested by McHose (1970) for computing average incentive, McHose et al. (1971) showed that the average incentive disparity between S+ and S-was equal in Groups 16/0-0 and 2-0 and less than that in Group 8-0. Consistent with the incentive averaging view, Groups 16/0-0 and 2-0 performed alike in S-and ran faster than Group 8-0.

Multiple hedonic memory: Memory for more than one hedonic event in rats

“…This conclusion, suggested by the present data, is consistent with previous findings. First, in conventional discrimination-learning situations, in which external cues such as brightness cues are relevant and hedonic memories are irrelevant, rats nevertheless employ hedonic memories (e.g., Capaldi, Berg, & Morris, 1975;Haggbloom, 1980;Haggbloom & Tillman, 1980). And in such conventional discrimination-learning situations, hedonic memory can have the same effect as in the unconventional discrimination-learning situation employed here: it can greatly elevate speed of responding on S-trials.…”

“…Retrieving the memory of 20 pellets on Trial 3 of the 20-0-20 series apparently resulted in that memory's elevating speed on Trial 2 of that series. 351 Rats remember hedonic events such as reinforcement and nonreinforcement, and these memories can exercise considerable control over responding in a wide variety of instrumental learning tasks (e.g., Capaldi, 1966;Capaldi, Verry, & Davidson, 1980;Grosslight & Radlow, 19S6;Haggbloom, 1980;Haggbloom & Tillman, 1980;Seybert, Mellgren, Jobe, & Eckert, 1974).Understanding this behavioral control, however, depends upon how many hedonic events are remembered in particular situations: the animal may remember only the immediately prior hedonic event (single-event hedonic memory) or two or more prior hedonic events (multiple-event hedonic memory). The single-event hypothesis has proved capable of explaining a widevariety of instrumental learning effects (see, e.g., Capaldi, Nawrocki, & Verry, 1982;Capaldi et a1., 1980).…”

Serial learning, interitem associations, phrasing cues, interference, overshadowing, chunking, memory, and extinction

“…This follows from a consideration of the effects of training level on N-R transitions that occur from a consistently nonrewarded alley of one brightness, for example, black, to a consistently rewarded alley of another brightness, for example, white. Early in training, such transitions will result in O-pellet cues' acquiring strong control over responding; they will increase resistance to extinction in the S+ alternative or decrease vigor of responding in the S-alternative (see, e.g., Capaldi, Berg, & Morris, 1975;Capaldi et al, 1984;Haggbloom, 1980b). Such evidence clearly suggests that brightness cues are not intense enough to seriously overshadow 0-pellet cues.…”

“…The shift to an extinction series employed here, however, has a marked advantage: N-R transitions have been examined in a wide variety of more orthodox instrumental learning situations and with effects similar to those obtained here. Thus, N-R transitions have been shown to reduce discriminative responding (e.g., Capaldi et al, 1975;Capaldi et al, 1984;Haggbloom, 1980bHaggbloom, , 1982, to retard reversal learning in discrimination tasks (e.g., Grosslight & Radlow, 1956;Haggbloom & Tillman, 1980), to reduce the simultaneous and successive negative contrast effects (Campbell & Meyer, 1971;Capaldi & Ziff, 1969), and to elevate resistance to extinction: in punishment situations (Capaldi & Levy, 1972), in escape situations (Seybert, lobe, & Eckert, 1974), in the S+ alternative of discrimination tasks (e.g., Capaldi et aI., 1975;Haggbloom, 1980b), and in reward schedule situations in animals (e.g., Capaldi, 1964Capaldi, , 1967Leonard, 1969) and people (e.g., Grosslight, Hall, & Murin, 1953). Similarities of the sort noted above support the view that serial learning, whatever its unique characteristics, may be viewed as continuous with various more orthodox instrumental learning situations.…”

“…According to an interitem view, in an N-R transition, cues associated with the nonreinforced item may become a signal for the subsequent reinforced item (see, e.g., Capaldi, 1964). If the "N" item becomes a strong signal for the "R" item, then, as can be seen, whenever the "N" item is presented, as, for example, in extinction or as the S-alternative of a discrimination task, responding will be elevated-resistance to extinction will be increased, discriminative responding will be reduced, and so on (see, e.g., Capaldi, Nawrocki, & Verry, in press;Haggbloom, 1980b). But in an N-R transition, cues produced by the nonreinforced item may not become a strong signal for reinforcement if some other stimulus simultaneously signals reinforcement.…”