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

Transcription

1 Animal Learning & Behavior 1984,12 (1), 7-20 Serial learning, interitem associations, phrasing cues, interference, overshadoing, chunking, memory, and extinction E. J. CAPALDI, DONNA R. VERRY, TIMOTHY M. NAWROCKI, and DANIEL J. MILLER Purdue University, West Lafayette, Indiana To experiments indicated that to approaches to serial learning are too extreme-the classical vie that it consists only of interitem associations and various recent vies that it involves no interitem associations. The novel assumption introduced here as that phrasing cues, normally conceptualized as merely segregating long series into smaller units or chunks, may also enter into associations ith items, thereby reducing interitem interference and facilitating serial learning. It as found that one item could become a signal for another item, an interitem association, or be overshadoed by a phrasing cue, such as a brightness and temporal cue, also signaling that item. The items ere,045-g pellets. Rats traversed a runay for items arranged in ordered series, pellets (Experiment 1)or (Experiment 2), Complete tracking of, for example, the series ould consist of fastest running to 10 pellets and sloest running to 0 pellets. In both investigations, the interitem association overshadoed as that beteen 0 pellets and the subsequent rearded item, 0-14 (Experiment 1) or 0-10 (Experiment 2). Either repetitions of the subpattem (Experiment 1) or merely the terminall0 pellet item (Experiment 2) ere phrased, both methods producing identical results. Overshadoing the O-pellet item produced superior serial learning, more rapid extinction, and, in Experiment 1, considerable elevation of responding hen the brightness phrasing cue as introduced in extinction, an effect said to be conceptually identical to spontaneous recovery and one demonstrating directly that phrasing cues are in reality overshadoing cues. It as suggested that many effects attributed to forgetting may be due to unrecognized overshadoing of memory cues by phrasing cues, giving rise to exaggerated estimates of forgetting. Serial learning, employed by Ebbinghaus (1885/ 1964) to investigate learning and memory, produced a theory of learning, the chaining hypothesis, hich ent virtually unchallenged for over 50 years. Recently, hoever, its central assumption, that of interitem associations in hich one item becomes the signal for the next, has been rejected by a variety of human serial learning models (e.g., Estes, 1972; Johnson, 1972; Restle & Bron, 1970). This retreat from Ebbinghaus has its counterpart in animal serial learning, lately the object of considerable interest. For example, Hulse and his co-orkers (e.g., Hulse, 1978; Hulse & Dorsky, 1977, 1979) have explicitly rejected interitem associations in favor of a cognitive rule-encoding model based on human models of the Restle type. Animal investigators normally speak in terms of trials, for example, a nonreinforced trial rather than a nonreinforced item. Because item terminology is more useful here, it is employed in this paper. According to the chaining vie, in the learning of a list of items, A- This research as supported by NSF Grant BNS to E. J. Capaldi. The authors' mailing address is: Department of Psychological Sciences, Purdue University, West Lafayette, IN B-C-..., item A is the stimulus for the response B, then item B becomes the stimulus for the response C, and so on. In addition to adjacent associations, remote associations are postulated, A being associated ith C but less strongly than ith B, and so on. Ifthe stimulus for an item is the preceding item, then pairing the to pairs in a subsequent paired-associate task (A-B; B-C) should produce positive transfer, a prediction not alays confirmed (see Young, 1968). Various other failings of the chaining model (see, e.g., Restle & Bron, 1970) suggest that serial learning cannot be explained solely in terms of interitem associations, even if they are conceptualized as S-S rather than S-R associations (Capaldi, Narocki, & Verry, 1983a). But e suggest that the complete rejection of iteritem associations that has occurred in recent years may be unarranted. We suggest this because, as has been emphasized elsehere, serial learning appears to have much in common ith varied reinforcement and discrimination learning, and certain findings in those situations have been interpreted thus far only in terms of interitem associations (Capaldi & Molina, 1979; Capaldi, Narocki, & Verry, 1982; Capaldi & Verry, 1981; Capaldi, Verry, & Davidson, 1980). 7 Copyright 1984 Psychonomic Society, Inc.

2 8 CAPALDI, VERRY, NAWROCKI, AND MILLER An example of an interitem association of direct concern in this report is that hich may be established hen a nonreinforced item is folloed by a reinforced item, an N-R transition. According to an interitem vie, in an N-R transition, cues associated ith 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, henever the "N" item is presented, as, for example, in extinction or as the S- alternative ofa discrimination task, responding ill be elevated-resistance to extinction ill be increased, discriminative responding ill be reduced, and so on (see, e.g., Capaldi, Narocki, & 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. When to cues simultaneously signal reinforcement and the presence of one reduces the behavioral control acquired by the other, e speak of overshadoing (e.g., Kamin, 1969). Overshadoing, e suggest, is commonplace in serial learning. Our vie, stated generally, is this: When the best predictor of an item is the previous item, an interitem association ill be formed. But if another cue is a better predictor of the item, because it is either more intense or more valid, it ill signal the item, and the previous item ill be more or less overshadoed. It is generally agreed that people can learn a long series of items more efficiently if they segment it into smaller units or chunks on the basis of some common property or relation (e.g., Boer & Winzenz, 1969; Restle & Bron, 1970). Thus, a 10-digit telephone number may be chunked into a 3-digit area code, a 3-digit prefix, and a 4-digit number. To of the numerous factors that have been shon to facilitate chunking (see, e.g., Boer, 1972) are similarityitems of the same color, shape, size, and so onand proximity-items occurring close together in space or time. "Phrasing cues" is one term applied to the numerous factors that have facilitated chunking. Recently, compelling evidence that animals chunk series, and on much the same basis as human subjects, has been provided by Hulse and his coorkers (e.g., Fountain, Henne, & Hulse, in press; Hulse, 1978; Hulse & Dorsky, 1977). Phrasing cues, e suggest, may not only segment long series into smaller chunks, but may also become signals for items. For example, a long temporal break in a series can be used to signal the first item occurring after the break, overshadoing the previous item as a signal. When an item is signaled eakly by the prior item and strongly by a phrasing cue, that item and all subsequent items joined by interitem associations constitute, according to the present vie, a chunk. The hypothesis introduced and tested here is that phrasing cues facilitate chunking, and therefore serial learning, because they overshado interitem associations, thereby reducing interference among items. Consider an example of interference that results hen an item signals to dissimilar items and ho such interference may be reduced by a phrasing cue. If item A signals the adjacent similar item A' (A- A') and A' signals the adjacent, but dissimilar, item B (A' - B), then generalization beteen the highly similar items A and A' ill give rise to considerable interference, item A signaling both A' and B. But if A signals A', and B is signaled not by A' but by a distinctive phrasing cue having little in common ith A, then interference ill be reduced, A signaling only A' ; in consequence, serial learning ill be facilitated. Necessarily, some nonlist event, call it X, must signal the first item in the list. Ifeach subsequent item in the list A-B-C-D... is signaled strongly by the preceding item, then e may have a list of only one chunk, X-A- B-C-D, the arros indicating associations. But say the interval beteen items C and D is longer than those beteen items A-B-C. This temporal phrasing cue, call it Y, may completely overshado C as a signal for D. In that event, e ould have a list of to chunks, X-A-B-C; Y-D. This vie as treated in the to investigations reported here by examining the effects of phrasing cues on extinction as ell as serial learning. The effects of phrasing cues on extinction have not previously been investigated. Of major concern here as the condition in hich, in an N-R transition, the R item as signaled not only by the N item, but by a phrasing cue, ith brightness and temporal phrasing cues beingemployedhere. It as expectedthat henever a phrasing cue overshadoed N as a signal for R, serial learning ould be facilitated because of reduced interference, and subsequent resistance to extinction ould be reduced, the latter prediction perhaps being unique among serial learning hypotheses, none of hich has as yet attempted to deal ith extinction. In each of the to investigations reported here, e employed series containing a subpattern that terminated in a O-pellet item, the O-pelletitem being folloed by a rearded item. The rearded item either as or as not signaled by some other cue, a change in brightness (Experiments 1 and 2) or a long temporal interval (Experiment 2). It as expected that the behavioral control exercised by the O-pellet item ould be reduced hen some other cue simultaneously signaled the subsequent rearded item. This reduction in control ould have to effects: it ould result in superior serial learning and it ould reduce resistance to extinction. EXPERIMENT 1 In order to facilitate a comparison of results, Experiment 1 employed procedures similar in many respects to those employed in investigations reported

3 SERIAL LEARNING 9 by Hulse and his co-orkers. In one preparation employed in Hulse's laboratory (see, e.g., Hulse, 1978), rats in a runay ere given a long series of items (.04S-g food pellets) constructed by repeating the five-item subpattern of food pellets On the first run don the runay, the rat ould be given 14 pellets, on the next run, 7 pellets, and so on. Runs ithin the subpattern ere separated by a 20 2S-sec interval; repetitions of the subpattern ere separated either by the same interval, the unphrased series, or by a IS-min interval, the temporally phrased series. The assumption as that chunking the series into the subpattern ould be more likely hen the series as phrased rather than unphrased. This should facilitate pattern learning, as indexed by running sloly to (tracking) the terminal O-pellet item of the subpattern. In agreement ith this reasoning, Hulse (1978) reported that tracking the O-pellet item occurred much sooner in the temporally phrased series than in the unphrased series, 4 8 repetitions versus 80 repetitions of the subpattern, a dramatic difference. Similar findings ere obtained in at-maze, here, in addition, spatial phrasing as also shon to be effective (Fountain et ai., in press). Fountain et al. reported that tracking the O-pellet item occurred much sooner in a spatially phrased group that received its first repetition of the subpattern in one arm of the T-maze, its next repetition in the opposite arm, and so on, than it did in either an unphrased group, hich received all repetitions on a given day in the same arm, or a mismatched group, for hich the phase cue as located beteen the 3- and I-pellet items, segmenting the series into a subpattern, hich is considered complex from a rule-learning viepoint. Experiment 1, like the investigations of Hulse and his co-orkers, employed a long series constructed from repeating the subpattern. The interval beteen all items, ithin and beteen subpatterns, as sec. The series as phrased using brightness cues. For Group GP (good phrasing), the first repetition of the subpattern occurred in a runay of one brightness, black or hite, the next repetition in the runay of the other brightness, and so on. For Group BP (bad phrasing), the brightness cue as changed beteen the 3- and l-pellet items, that is, / /, and so on, the slashes indicating a change in alley brightness. For Group GP, except for the first daily presentation of the 14-pellet item, to cues signaled the 14-pellet item, the terminal O-pellet item of the subpattern and the change in alley brightness. For Group BP, again except for the initial 14-pellet item of the day, only one cue reliably signaled 14 pellets-the O-pelletitem. For Group GP, the change in alley brightness could overshado the O-pellet item as a signal for 14 pellets, but such overshadoing as not possible in Group BP. According to the present hypothesis, as ill be explained in detail later, ith overshadoing, Group GP should track 0 pellets better than Group BP and should extinguish faster than Group BP, since both effects are due to a common cause, 0 pellets being a eaker signal for 14 pellets for Group GP than for Group BP. In Experiment 1 there ere 2 days of extinction, and miday through the extinction trials on each day alley brightness as changed. If the change in alley brightness did indeed become a strong signal for 14 pellets for Group GP, overshadoing the O-pellet item, then the change in brightness should produce increased vigor of responding in Group GP but not in Group BP. Method SabJeeu. The subjects ere eight naive male albino rats, 80 days old on arrival at the laboratory, purchased from the Holtzman Co., Madison, Wisconsin. Apparatus. The apparatus consisted of to adjacent runays, identical except for brightness. One as black, and the other as hite. The startboxes, also black or hite, ere 21.6 cm long; the goalboxes ere em long. Each alley as 8.57 cm ide and a total of em long; each as enclosed by cm sides covered by a ire-mesh top on a hinged frame. Loering the brass startbox door started a completely silent.01-sec digital clock that as stopped hen a photobeam, located em beyond the startbox door, as broken by the rat. Pellets (.045-g Noyes) could be placed in a goal cup (3.8 x 3.8 x.95 cm) at the end of the runay. The pellets ere not visible before the photobeam as broken. A brass door confined the rat to the goalbox, PretralniDI. On arrival at the laboratory, the rats ere caged individually and alloed ad-lib food and ater for 5 days. On Days 1-9, each rat as handled for 1 min and then fed the daily ration in the home cage, 24-g Lab Blox, a laboratory rat cho made by the Wayne Pet Food Company. On Day 10, each rat as fed g pellets in the home cage. On Days 11-12, each rat as exposed to each runay for 1 min and then returned to the home cage, here it as fed.045-g pellets, folloed by the daily ration. Throughout all phases of the experiment, all pellets eaten by the rat ere subtracted from the 14-gdaily ration. Experimental tralmnl. There ere to groups of four rats each. Each rat received repetitions of the subpattern, , ith to repetitions on Days 1 and 2 and four repetitions on Days The interval beteen all items, ithin the subpattern and beteen repetitions of the subpattern, as sec. Four rats, to from each group, ere taken into the experimental room from the colony room. The rats ere run in a different order each day, and each rat received all items of the series before the next rat as run. After the last rat as run, the animals ere returned to their home cages here, after 10 min, they ere fed their daily ration. About 3 sec after the rat as placed in the startbox, the startbox door as loered. The rat as alloed 60 sec to reach the goalbox to receive hatever item as scheduled on that run. If the rat did not make it in 60 sec, it as placed in the goalbox. Failures to reach the goalbox ere rare. On o-pellet runs, the rat as confined to the unbaited goalbox for 15 sec. On reinforced runs, immediately after eating the pellets, the rat as removed from the goalbox and placed in a aiting cage, ith ater available. About sec later, the rat as given the next run of the series. For Group GP, the first repetition of the subpattern occurred in an alley ofone brightness, black or hite, the next repetition in the runayofthe otherbrightness, and so on. For Group BP, the brightness cue as changed beteen the 3- and l-pellet items, that is, / /, and so on, the slashes indicating a change in alley brightness. On Days 1 and 2, the black runay as presented first. Thereafter, the hite runay as presented first on odd days and the black runay as presented first on even days.

4 10 CAPALDI, VERRY, NAWROCKI, AND MILLER On Days 12 and 13, each rat received 10 nonreinforced runs, all at sec intervals. On Day 12, for each rat, the first five runs occurred in the black runay, the next five in the hite runay, the opposite order of runay presentation being used on Day 13. Except for the fact that all runs terminated in nonreinforcement, the conditions in extinction ere as in the acquisition phase. On rearded trials, the pellets ere placed noiselessly in the goal cup from a cloth-lined cup. To control for odors, an open cannister of pellets as placed near the goalbox. Results There ere to repetitions of the subpattern on Days 1 and 2 and four per day thereafter. Speed of running on each of the runs of the subpattern for Days 1 and 2 combined and for each of Days 8-11 are shon in Figure 1. Figure 1 shos that, on Days 1-2, neither group tracked the O-pellet item, but that from Day 8 on, Group GP, but not Group BP, did track the O-pellet item. An analysis of variance as performed over the entire serial learning phase, using as factors groups, repetitions ofthe subpattern, runs, and days, Days 1 and 2 being combined into a single' day in the analysis. The analysis revealed that the groups did not differ significantly (F < 1). Hoever, they did perform differently over the runs of the subpattern, significant differences being obtained for the interactions of groups X runs [F(4,24) =4.12, P <.01] and groups X day X runs [F(36,216) =1.54, p <.OS]. Subsequent Neman-KeuIs tests based on the significant triple interaction revealed that Group GP tracked the O-pellet item, running, ith one exception, more sloly to it than to any other item on Days 8, 9, 10, and 11; on Day 9 the l-pellet and 0- pellet speeds did not differ (other ps <.01). Statistically, there as no evidence at any point in training that Group BP as able to anticipate the O-pellet item. On Days 9-11, Group GP ran more sloly than Group BP to the O-pelletitem (ps<.01), but no other difference beteen the groups as significant. Figure 2 shos running speed on each of the 10 runs of each day of extinction for each group. Three important relationships may be discerned in Figure 2. First, on each day of extinction, speed over runs declined more rapidly in Group GP than in Group BP. Second, on each day ofextinction, hen alley brightness as changed beteen Runs 5 and 6, Group GP, but not Group BP, shoed a large and immediate increase in running speed. Third, on each day ofextinction, Group BP, but not Group GP, shoed an increase in running speed from Run 6 to Run 7. There ere to reasons for taking the speed increases from Runs 5 to 6 in Group GP and from Runs 6 to 7 in Group BP seriously. These increases occurred on each of the 2 extinction days and, for each group, at a point here in the prior acquisition phase 14 pellets had been provided. In acquisition, Group GP had received 14 pellets coincident ith a change in alley brightness and Group BP had received them after a O-pellet run had occurred in a changed alley. An analysis of variance over the speeds shon in Figure 2 revealed that the groups differed significantly [F(1,6) =52.34, p <.01], and that speed over runs declined more rapidly in Group GP than in Group BP, the groups X runs interaction being significant [F(4,24) = 9.72, p <.01]. In order to evaluate tj) <, 105 ::IE 0 90 '-"" c tj)...i 45 <C I- 0 ~ I- q TRIALS IN ~._._. B P G P, 9 EACH 10 DAY 11 Figure 1. Speed of running for Groups GP and BP on each of the runs of the subpattern for Days 1 and 2 combined and on each of Days 8-11.

5 SERIAL LEARNING o 120 en <, ::E 100 U c 60 a. en 40..J «20 ~ _.-.+ B P.; _.+._ I \ I +._... i "' I i "' I \. I \ i DAY 1 TRIALS IN G P DAY 2 EAC H DAY Figure 2. Speed of running on each of the 10 runs of each day of extinction for each group. the effect of the brightness change from Runs S to 6, an analysis as performed using speeds from Runs S and 6 for each group on each day of extinction. Importantly, the groups x runs interaction as significant in this analysis [F(l,6) = 20.28, p <.01]. Subsequent Neman-Keulsposttests indicatedthat Group GP, but not Group BP, shoed a significant increase in speed from Run S to Run 6 (p <.01). A similar analysis as performed for Runs 6 and 7. The groups x run interaction as significant [F(1,6) = 11.80, p <.01], and subsequent Neman-Keuls tests indicated that Group BP, but not Group GP, shoed a significant increase in speed from Run 6 to Run 7 (p <.01). The decline in speed from Run 6 to Run 7 in Group GP as not significant. Sinc~, in acquisition, Group GP ran more sloly than Group BP, it as considered advisable to perform an additional analysis to better determine if, indeed, Group GP as less resistant to extinction than Group BP. The speeds of each group on the last day of acquisition, Day 11, ere compared ith those in extinction, Days 1 and 2 of extinction being combined into a single day. Group BP, of course, ran more rapidly than Group GP [F(I,6)=7.31, p<.03]. Importantly, hoever, the groups x days interaction as significant [F(l,6) =20.49, p <.01]. Subsequent Neman-Keuls tests based on the groups x days interaction revealed that-group GP, but not Group BP, ran significantly more sloly in extinction than on the last day of acquisition (p <.01), leaving little doubt that Group GP as less resistant to extinction than Group BP. Discussion In Experiment 1, 0 pellets as better tracked by Group GP than by Group BP, a finding consistent ith that previously obtained by Fountain et al. (1983) using spatial and temporal phrasing cues rather than the brightness phrasing cues used here. Hoever, to novel and, e suggest, revealing findings ere obtained in Experiment 1. First, Group GP as much less resistant to extinction than Group BP. Second, in extinction a change in alley brightness as associated ith significantly increased vigor of responding in Group GP but not in Group BP. Consider these to extinction findings in turn. First, according to the present hypothesis, the more strongly O-pellet items, hich ofcourse occur exclusively in extinction, signal reinforcement, the more vigorous ill responding be in extinction. The capacity of 0 pellets to signal reinforcement as greater in Group BP than in Group GP. This as so because, for Group BP, 0 pellets in acquisition as a signal for 14 pellets. Hoever, for Group GP, 14 pellets as signaled not only by 0 pellets, but also by a change in alley brightness, the latter cue overshadoing the former, and apparently to a significant extent. Additional evidence that, for Group GP, the change in alley brightness overshadoed 0 pellets as a signal for 14 pellets as provided in extinction. When, on each of 2 days, alley brightness as changed in extinction, Group GP, but not Group BP, shoed a marked increase in vigor of responding, demonstrating clearly that a change in alley brightness as a signal for 14 pellets for Group GP but not for Group BP. We may infer

6 12 CAPALDI, VERRY, NAWROCKI, AND MILLER from this finding that the rats in Group GP remembered the alley brightness from the previous run, compared it ith that on the current run, and, if the to differed, ran fast in anticipation of a 14-pellet reard. This ould appear to involve the same general sorts of processes of interest in the delayed matchingto-sample situation (e.g., Maki, Moe, & Bierley, 1977). Whenever an external stimulus overshados 0 pellets as a signal for reard, extinction ill be rapid. This explains hy folloing ell-established discrimination learning in hich the positive stimulus is rearded and the negative stimulus is 0% rearded, extinction is rapid-as rapid as it is in a consistently rearded control group (e.g., Bron & Logan, 1965). In this instance, the positive brightness stimulus rather than the O-pellet item is the signal for reard in the discrimination group. Such a discrimination group, then, is similar to Group GP here in that some stimulus other than the O-pellet item is a signal for reard. Above, e emphasized the strength of an interitem association, 0-14, in order to explain extinction. Emphasizing this same interitem association, but no in describing ho its strength contributes to interitem interference, ill serve to explain the better serial learning achieved by Group GP than by Group BP. Let us see ho the brightness phrasing cue, by becoming a signal for 14 pellets for Group GP, reduced interitem interference and thus facilitated serial learning. The capacity of an item to signal another may be acquired directly or indirectly through generalization from items similar to it (Capaldi & Molina, 1979; Capaldi et ai., 1980). When one item precedes another, the first may directly acquire a tendency to signal the second. But the signal tendency acquired directly by an item may differ from the signal tendencies supplied indirectly to that item from other items, producing considerable interference. Thus, an item that has acquired a strong direct tendency to signal 0 pellets may nevertheless produce poor tracking of 0 pellets if indirectly acquired tendencies supplied by highly similar items strongly signal not 0 pellets, but reinforcement. This describes hy tracking of 0 pellets as poor in Group BP. In Groups BP and GP, the l-pellet item as the discriminative stimulus preceding 0 pellets. We may assume, then, that in both groups the I-pellet item as an equally strong direct signal for 0 pellets, and to the extent that tracking of0 pellets occurred in each group it as because the l-pellet item became a direct signal for 0 pellets. But this direct signal capacity, hich produced tracking of 0 pellets, as opposed by indirect or generalized signal capacity of other items that signaled reard. Most notably, the l-pellet item ould receive considerable indirect signal capacity from the O-pellet item. But, as e sa above in connection ith extinction, the O-pellet signal for 14 pellets as much stronger for Group BP than for Group GP. Thus, the indirect tendency of the l-pellet item to signal 14 pellets as much stronger for Group GP than for Group BP, hich explains the differences beteen these groups in both tracking behavior and extinction. Deserving comment is the finding, not directly relevant to the major concerns of this report, that on each of 2 days of extinction Group BP shoed a significant increase in running speed from Run 6 to Run 7. This finding as obtained presumably because, in acquisition, Group BP as rearded ith 14 pellets after a O-pellet run had occurred in a changed alley. Thus, hen these conditions prevailed in extinction, Group BP shoed an elevation in speed from Run 6 to Run 7. For Group BP, then, although opellets as a strong signal for 14 pellets, a O-pellet run after a change in alley brightness as an even stronger signal. Of course, runs in another alley alone did not predict 14 pellets for Group BP, precluding overshadoing of 0 pellets by brightness cues as for Group GP. EXPERIMENT :1 Experiment 1 provided strong evidence that phrasing cues are, in effect, overshadoing cues that eaken interitem associations. But, although the method of phrasing used in Experiment 1 (hich, to facilitate comparison of results, as similar to that used in Hulse's laboratory) as adequate for testing the present hypothesis, it as not completely optimal for that purpose. Experiment 2 differed from Experiment 1 in to major respects. First, series ere phrased in a manner more in conformity ith the present hypothesis. Second, in order to provide certain additional tests ofthe present hypothesis, phrasing cues ere removed for some groups prior to extinction. Consider ho the long series as phrased for Group GP in Experiment 1. One complete repetition of the sub pattern occurred in one brightness alternative, the next complete repetition occurred in the other brightness alternative, and so on. Call this procedure, for convenience, phrasing complete repetitions of the subpattern. According to the present hypothesis, the findings obtained for Group GP ere not dependent upon phrasing complete repetitions of the subpattern, something hich might, hoever, be emphasized in a rule-learning model (see, e.g., Fountain et al., 1983). Rather, according to the present hypothesis, Group GP behaved as it did because the first item of the repetition of the subpattern, 14 pellets, occurred in a changed brightness alternative. Such first-item phrasing, as e shall call it, is sufficient, according to the present hypothesis, to allo the brightness change to overshado the 0 pellet item as a signal for reinforcement. Experiment 2 tested this vie. It examined first-item phrasing by

7 SERIAL LEARNING 13 employing hat may be conceptualized as a short four-item series, Experiment 2 employed a brightness phrasing condition, as in Experiment I, and a temporal phrasing condition. Phrasing occurred as follos. The series as segmented into to subpatterns, the initial three items, , and the terminal item, 10. The initial three items occurred in one brightness alternative (or at a short interval beteen items), the terminal 10-pellet item in another brightness alternative (or after a long interval). Also employed in Experiment 2 as an unphrased group hich received all items at the same short interval and, on a given day, in the same brightness alternative. In the Fountain et al. (1983) investigation, hich, as indicated, employed repetitions of the subpattern, for some groups repetitions ere separated by a long interval (temporal phrasing) and for others they occurred in different arms of at-maze (spatial phrasing). Removal of the phrasing cues in the Fountain et al. (1983) investigation disrupted tracking of the subpattern, ith such disruption being more severe in the temporal phrasing group than in the spatial one. Our interpretation of such disruption is that removal of the phrasing cue alloed the terminal O-pellet item ofthe subpattern to no become a strong signal for 14 pellets. Furthermore, here disruption as greater, as it as for the temporal group, the more strongly as 0 pellets converted into a signal for 14 pellets. From this it follos that the more disrupted groups should also sho greater subsequent resistance to extinction; as the capacity of0 pellets to signal reinforcement increases, so too should resistance to extinction. This hypothesis as tested in Experiment 2. In Experiment 2, half the rats that had received a brightness or temporal phrasing cue in Phase 1 had this cue removed in Phase 2, thus being shifted to the unphrased series. All remaining rats, including those in the unphrased group, ere trained in Phase 2 as they had been in Phase 1. At the termination of Phase 2, all rats ere extinguished. Method SubJeetI. The subjects ere 30 rats of the same description as in Experiment 1. Apparatal. The apparatus as the same as that used in Experiment 1. PretrlDi... Pretraining as identical to that used in Experiment 1. At the end of pretraining, the rats ere divided into five groups of six rats each. There ere three experimenters, each of hom ran to rats from each group. There ere to replications, each experimenter running five rats in each replication, one from each group. Phue 1 procedure. All rats received the series This series occurred tice each on Days 1 and 2 of experimental training and four times each day on Days 3-9. Thus, the interval separating repetitions of the series as min. For four of the groups in Phase 1, the series as segmented into the initial three items, , and the terminal item, 10. For the fifth group, Group N-N, the series as unphrased, all items of the series occurring at a 20- sec interval in the black (B) runay on odd days and in the hite (W) runay on even days. Groups T-T and T-N ere treated exactly as as Group N-N in Phase 1, ith one exception: A 10 min interval (approximately) separated the third and fourth items of the series. Groups B-B and B-N ere also treated as as Group N-N, ith one exception: The fourth item ofthe series occurred in an alley of a brightness that as different from that of the preceding three items, that is, BBBW on odd days and WWWB on even days. All other aspects of the experimental procedure in Experiment 2 ere as in Experiment 1, except for the folloing: Each experimenter brought five rats into the experimental room, one from each group. Running orders ere randomized daily. Each rat as run such that it received all four runs of a series before receiving the next repetition of the series 10-20min later. Phue 2 procedure. Phase 2 training occurred on Days It as identical to Phase 1 except for the folloing. On all days of Phase 2, including the first 2 days, there ere four repetitions of the series. Groups T-T, B-B, and N-N continued to be trained as in Phase 1, ith Groups T-N and B-N being trained as as Group N N; that is, for Groups T-N and B-N, the temporal and brightness phrasing cues, respectively, ere removed. ExtInetIoD. Extinction occurred on Days Each rat received a series of four nonreinforced runs in succession at a 2O-sec interval. There ere four of these four-run series each day, the interval separating repetitions of the series being about 10 min. All runs occurred in the hite runay on Days 18 and 20 and in the black runay on Day 19. All other aspects of the procedure ere as in Experiment 1. Results Figure 3 shos speed of running on each of the four runs of the series on Days 1 and 2 combined and on each day thereafter in Phase 1, for Group N-N, for Groups T-T and T-N combined (T), and for Groups B-B and B-N (B). Perfect tracking of the series ould consist of slo running on O-pellet runs, somehat faster running on 2-pellet runs, and fast and nondifferential responding on the to lo-pellet runs of the series. At one extreme as Group N-N, hich deviated substantially from perfect tracking, and hich, even hen tracking in Phases 1 and 2, ran only slightly more sloly on 2 and O-pellet runs than on 10-pellet runs. At the other extreme, perfect tracking as achieved by Groups T T and T-N on the final days of Phase 1, these groups running more sloly on 2- and O-pellet trials as early as Day 3 of Phase 1. In Phase 2, the nonshifted group, Group T-T, maintained perfect tracking ith little exception. In beteen these extremes as the nonshifted Group B-B, hich finally achieved perfect tracking on some of the final days of Phase 2. In Phase 1, and on the earlier days of Phase 2, Group B-B deviated from perfect tracking in running equally sloly on 2- and O-pellet runs and in running more sloly to the terminal than to the initial 10 pellet item. An analysis ofvariance, using groups, runs, repetitions of the series, days, and experimenters as factors, as performed over Phase 1. In this analysis, Days 1 and 2 ere treated as a single day and Groups T-T and T-N ere treated as a single group, as ere Groups B-B and B-N. This analysis revealed significant differences for groups [F(2,21) =S.88, p <.01],

8 14 CAPALDI, VERRY, NAWROCKI, AND MILLER tj) 100 <, ::::E C a. 50 ~ tj)...j <C a ~ 25 ~ t!v\j\}~ - B - N - T TR IALS I N EACH DAY Figure 3. Speed of running on each of the runs of the series on Days 1 and 2 combined and on each of the days of Phase 1 thereafter for each of the five groups. for groups X runs [F(6,63) = 1.86, p <.005], and for groups x runs X days [F(42,441) = 1.86, p <.005]. Subsequent Neman-Keuls tests based on the significant groups X runs X days interaction indicated that by the end of Phase 1 even Group N-N as giving some evidence of tracking. Some important differences revealed by the Neman-Keuls tests ere as follos. The T groups ran more sloly on 2- and 0 pellet runs than on 10-pellet runs as early as Day 3 and, on each of the last 3 days of Phase 1, manifested perfect tracking (ps <.05 or better). The B groups, by as early as Day 4, ran more sloly on 2- and O-pellet runs than on the initial lo-pellet run; hoever, on many of the days of Phase 1 (3, 5, 7, 9), the B groups ran more sloly on the terminal than on the initial 10-pellet runs (ps <.05 or better). Moreover, on some days (3, 4, 5, 7), running as no faster on the terminal run than on 2- and O-pellet runs. By Day 8, Group N-N ran faster on its initiall0-pellet run than on each of its subsequent runs (ps <.05). On Day 9, Group N-N as sloer on its 2-pellet run than on its terminallo-pellet run (p<.05). Figure 4 shos speed on running on each of the four runs of the series on each of the days of Phase 2 for Group N-N and the to unshifted groups, Groups T-T and B-B. Group T-T, ith minor exceptions to be noted, shoed perfect tracking on each of the days of Phase 2. In Group B-B, tracking improved over Phase 2 until, by the final days, it as tracking all items very ell indeed. Group N-N, although running much faster than Groups T-T and B-N on 2- and O-pellet trials, shoed some evidence of tracking, mainly in running more sloly on 2- and O-pellet runs than on lo-pellet runs. Figure 5 shos speed of running on each of the four runs of the series on each of the days of Phase 2 for Group N-N and the to shifted groups, Groups T-N and B-N. Tracking as disputed in both shifted groups, but earlier and more drastically in Group T-N than in Group B-N. For example, on Day 2 of postshift, Group T-N ran equally rapidly on all runs, hereas Group B-N continued to track reasonably ell except for running sloly on the terminal 10-pellet run, a tendency that as also strong in Group B-N in Phase 1. Over days, Group B-N sped up on the 2- and O-pellet runs and, by the end of Phase 2, as tracking about as ell as Group N-N. Group T-N, hoever, continued to track more poorly than Groups B-N and N-N, mainly in failing to slo don on 2-pellet runs. An analysis of variance performed over Phase 2 revealed that the groups did not differ significantly [F(4,15) = 2.50, p >.05]. Hoever, significant differences ere obtained for groups x runs [F(12,4S) = 6.74,p<.001] andfor groups x runs x days [F(84,13s) =1.45, p <.05]. Some important findings revealed by subsequent Neman-Keuls tests, breaking don the significant groups x runs X days interaction, ere as follos. Group T-T shoed perfect tracking on each of the days of Phase 2 except for Days 1 and 4. On Day 1, the 2- and O-pellet runs failed to differ, and on Day 4, running on the terminal 100pellet run as sloer than it had been on the initial 10 pellet run (p <.05). Group B-B shoed perfect tracking on Days 7 and 8, missing it on Day 9 because of sloer running on the terminal than on the initial 10 pellet run (ps <.05 or better). On most of the days of Phase 2, Group T-N ran equally rapidly on all runs.

9 SERIAL LEARNING 15 o (J) 125 <, ::IE o 100 Q 75 Q. (J) 50...J c:a: I I- q:!, B-B - N-N - T-T,,,,,,,,,,,,,, TRIALS IN EACH DAY,, 8 Figure 4. Speed of running on each of the four runs of the series on each of the days of Phase 2 for Group N-N and for the to unshifted groups, T-T and B-B..- o W(J) 1 25 <, 100 ::IE Q 75 ~ \ -.».-.r" _.A \ \ \ \... Q. (J)...J 50 c:a: I- 0 I- 25 ~,, 1.-._._. B - N "'1"1'" 2 3 -N-N 4 TRIALS IN,, 5 EACH.'- _ -4 T -,,,, 6 7 DAY N,,, 8 Figure 5. Speed of running on each of the four runs of the series on each of the days of Phase 2 for Group N-N and for the to shifted groups, T-N and B-N. By Day 8, hoever, Group T-N ran more rapidly on its initial to-pellet run than on any other run (ps <.OS). On each of the last 3 days of postshift, Groups N-N and B-N ran more sloly on 2- and O-pellet runs than on IO-pellet runs, indicating that by the end of Phase 2 these groups ere tracking about equally ell and better than Group T-N. In extinction, all rats received four extinction series of four runs each on each of 3 days. Speeds on the first run of each of the four series ere summed each day, as ere speeds on Run 2, and so on. These mean speeds are shon in Figure 6 for each group on each day of extinction. Group T-N ran fastest in extinction, Groups N-N and B-N ere intermediate, and Groups T-T and B-B ere sloest, ith Group T-T being sloer than Group B-B on the final runs of Day I of extinction. An analysis of variance over the 3 days of extinction revealed the folloing. There

10 16 CAPALDI, VERRY, NAWROCKI, AND MILLER u <I'l <, ::E u Cl "' V'l... 4: I- o I o - a-a B-N - N-N T-N - T-T 123 TRIALS IN EACH DAY Figure 6. Speed of runmng for each of the five groups on each of the four runs of the extinction series on each day of extinction. Discussion In Group GP of Experiment 1, complete repetitions of the subpattern ere phrased. In contrast, in Phases 1 and 2 of Experiment 2, Groups B-B and T-T received first-item phrasing only. Such first-item phrasing, it as suggested, should be sufficient to allo the change in brightness, Group B-B, or the longer interitem interval, Group T-T, to overshado the O-pellet item as a signal for reinforcement. As indicated, such overshadoing should result in better tracking of the subpattern and subsequent rapid exere significant differences due to groups [F(4,15) = 9.94, p <.01], runs [F(3,45) = , P <.001], groups X runs [F(12,45) =6.06, p<.001], and groups x runs x days [F(24,96) = 1.99, p <.05]. Subsequent Neman-Keuls tests, breaking don the significant group effect, revealed that Group T-N ran faster than all other groups and that Groups T-T and B-B, hich did not differ overall, ran faster than Groups N-N and B-N, hich did not differ overall (ps <.05 or better). Evidence that Group T-T extinguished more rapidly than any other group as provided by breaking don the groups x run x days interaction. Neman-Keuls tests revealed that, on Day 1 of extinction, Group T-T ran more sloly on Runs 3 and 4 than did any of the other groups (ps <.05 or better). An examination of Figure 6 indicates that on Runs 3 and 4 of Day 1, Group T-Tas running about as sloly as it or any group ran at any point in extinction training, suggesting a floor effect. tinction. Groups T-T and B-B of Experiment 2 did, indeed, sho superior tracking and more rapid extinction than the remaining groups. In this, they ere like Group GP of Experiment 1, in hich complete repetitions of the subpattern ere phrased. Vieing the findings of Experiments 1 and 2 together strongly suggests that the behavior of Group GP, like that of Groups B-B and T-T, as due to first-item phrasing only. First-item phrasing clearly identifies the strength of the interitem association beteen the O-pellet item and the subsequent reinforced item as the major factor in the results reported here. Although our phrasing procedure and series in Experiment 2 differed substantially from those employed by Fountain et a1. (1983), our results ere highly similar to theirs. In the Fountain et a1. (1983) investigation, tracking behavior as more disrupted by removal of a temporal phrasing cue than it as by removal of a spatial phrasing cue. Similar findings ere obtained in our Experiment 2, except that there temporal phrasing as compared ith brightness phrasing rather than ith spatial phrasing. Our interpretation of such disruption is that removal of the phrasing cue, hich overshadoed the O-pellet item, no alloed that item to become a signal for 10 pellets in the series. The signal strength no acquired by the O-pellet item then generalized to the 2-pellet item, increasing speed and reducing tracking. The greater the disruption in tracking, according to the present hypothesis, the more strongly is 0 pellets converted into a signal for 10 pellets and the greater should resistance to extinction be. Consistent ith this deduction, Group T-N, hich shoed greater disruption of tracking behavior than did Group B-N, also shoed greater resistance to extinction than did Group B-N. Indeed, the relationship beteen poor tracking performance and increased resistance to extinction included all five groups of Experiment 2. Group T-T shoed the best tracking performance and, on Day 1, extinguished more rapidly than Group B-B, hich shoed the next best tracking performance and extinguished next most rapidly. Group N-N tracked about as ell as Group B-N and better than Group T-N, and extinguished about like Group B-N, both groups extinguishing more rapidly than Group T-N. This close relationship beteen tracking performance, on the one hand, and extinction performance, on the other, supports the present vie that the to behaviors are closely related and due to the same mechanism, the strength, or lack of strength, of the 0-10 interitem association. It is suggested that the no-phrasing treatment is more similar to the brightness phrasing treatment than to the temporal phrasing treatment and that similarity relations among these treatments can explain the effects, on tracking behavior and extinction, of removing phrasing cues. Overshadoing of

11 SERIAL LEARNING 17 the O-pellet item as least in Group N-N, for hich no explicit overshadoing cue as provided, intermediate in Group B-B, and greatest in Group T-T, hich shoed the best tracking behavior and the fastest extinction. In terms of overshadoing, then, no phrasing is more similar to moderately effective brightness phrasing than to more completely effective temporal phrasing. On this basis, the shift no-cue training in Phase 2 as more similar to the Phase 1 training received by Group B-N than to that received by Group T-N. Thus, more of hat as learned in Phase 1 as relevant in Phase 2 for Group B-N than for Group T-N, and so Group B-N shoed less disruption (greater transfer) in Phase 2 than did Group T-N. GENERAL DISCUSSION The hypothesis introduced and tested in both investigations reported here as that phrasing cues can overshado interitem associations, thereby decreasing resistance to extinction and facilitating serial learning by reducing interitem interference. This hypothesis as confirmed in Experiments 1 and 2, hich employed series containing subpatterns terminating in a O-pellet item, the O-pellet item being folloed by a rearded item. In Experiment 1 complete repetitions of the sub pattern ere phrased, hereas in Experiment 2 only the rearded item as phrased. In either event, hen the rearded item as reliably signaled by some other cue, a change in brightness, or a long temporal interval, tracking of the subpattern as facilitated and resistance to extinction as reduced. The close relationship beteen serial learning performance and extinction performance is compatible ith the folloing vie. If the O-pellet item is the best predictor of reard, it ill become a signal for reard and an interitem association ill be formed. If, hoever, some other cue also signals reard, the O-pellet item may be overshadoed by that cue, resulting in a eakened, perhaps even totally nonfunctional, interitem association. The eaker the interitem association beteen the O-pellet item and the subsequent rearded item, the more rapid the extinction and the better the serial learning due to decreased interitem interference. Additional strong evidence that phrasing cues are actually overshadoing cues as provided in Experiment 1 hen, in Group GP, a change in alley brightness miday through the extinction trials resulted in a dramatic increase in vigor of responding. Granting that rapid extinction and facilitated serial learning ere due here to 0 pellets' being a relatively eak signal for reard, there are to alternative accounts to overshadoing, both rejected here, as to ho such eakening might have occurred-generalization and retrieval, respectively. According to the generalization vie, 0 pellets become a signal for re- ard in one context, for example, hen the brightness alternative changed, but as not a signal for reard in ane, generalized context, for example, hen the brightness alternative did not change. The generalization vie is highly incompatible ith previous findings shoing that context can be altered much more extensively than as the case for Group GP or Group B-B here, and 0 pellets ill continue to be a strong signal for reard (e.g., Capaldi, Capaldi, & Kassover, 1970; Ross, 1964). According to the retrieval vie, the relatively eak capacity of 0 pellets to signal reard as not due to overshadoing, but to a failure to retrieve O-pellet cues on rearded runs. The retrieval approach is rejected here for to reasons. First, the dramatic increase in speed of responding shon by Group GP in extinction hen alley brightness changed indicates, as previously mentioned, that events from the previous run ere retrieved and compared ith events on the current run much as in delayed matching-to-sample experiments. Second, as ill become clear belo, there is considerable evidence from prior investigations that indicates that a O-pellet event in one alley, say, a hite one, is retrieved on the subsequent runs in another alley, say, a black one, and can acquire a strong tendency to signal reard. Why did overshadoing occur here? One cue may overshado another because of its intensity or because it is the more valid predictor of reard (see, e.g., Hall, Mackintosh, Goodall, & Oal Martello, 1977; Kamin, 1969). Considering the brightness phrasing cue first, e recognize that, in Group GP of Experiment 1 and Group B-B of Experiment 2, the change in alley brightness could have overshadoed the O-pellet cue as a signal for reard because of greater intensity. We suggest, hoever, that it is more consistent ith all available evidence to assume that validity, rather than intensity, as responsible for overshadoing in Groups GP and B-B. In particular, evidence from brightness differential conditioning suggests that if brightness cues overshado 0 pellet cues, they do so for reasons of validity rather than intensity. This follos from a consideration of the effects of training level on N-R transitions that occur from a consistently nonrearded alley of one brightness, for example, black, to a consistently rearded alley of another brightness, for example, hite. Early in training, such transitions ill result in O-pellet cues' acquiring strong control over responding; they ill 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 overshado 0 pellet cues. Hoever, it N-R transitions are introduced later in discrimination training, O-pellet cues ill fail to acquire control over behavior (Haggbloom,

12 18 CAPALDI, VERRY, NAWROCKI, AND MILLER 1980a). This finding suggests that the animal learns that the brightness cues are more valid predictors of reard than the O-pellet cues, and as a result the 0 pellet cues are overshadoed. Ho could validity produce overshadoing here in Groups GP and B-B? Recognize that although the O-pellet item as itself alays folloed by reard for those groups, it as highly similar to other items signaling nonreard, 1 pellet (Group GP), or 2 pellets (Group B-B) and as in this sense invalid. To suggest that the validity of the O-pellet item as reduced because of its similarity to other items is not arbitrary; the alternative is to assume that validity is independent of similarity, hich seems unreasonable. It is generally recognized that organisms may employ various strategies that result in series' becoming easier to learn (e.g., Boer, 1972; Fountain et al., 1984; Restle & Bron, 1970). Ho organisms come to select one strategy over another is an interesting issue. The hypothesis introduced above, that item validity decreases as interitem similarity increases appears to have some relevance for ho strategies come to be selected. Ifthe reduction in validity that accompanies increased item similarity ere to lead to a decreased tendency to form interitem associations and an increased tendency to associate items ith phrasing cues, interitem interference ould be reduced and the task of learning the series greatly simplified. Ho could the organism come to adopt such an effective strategy? Several theories suggest that the associability (a) of a stimulus decreases if it predicts less accurately than other stimuli in the situation (e.g., Mackintosh, 1975; Pearce & Hall, 1980). Thus, given the relationship beteen validity and similarity suggested above, the associability approach is one mechanism capable of explaining hy, as interitem similarity increases, the tendency to associate items ith valid phrasing cues, rather than ith relatively less valid items, should increase. Group T-T shoed much better tracking and faster extinction than Group B-B. On this basis, it may be concluded that O-pellet cues ere more effectively overshadoed in Group T-T than in Group B-B. This may be explained by assuming that although overshadoing in Group B-B (and Group OP) occurred for reasons of validity rather than intensity, in Group T-T overshadoing may have been due to both factors. For purposes of discussion, cues associated ith the first run after a long temporal interval are referred to as first-run cues. The greater effectiveness of first-run than of brightness cues as overshadoing cues may be related to their considerable intensity. This approach explains not only the effectiveness of first-run cues here but also directly hy long intervals beteen series of massed extinction trials are associated ith increased vigor of responding, so-called spontaneous recovery. In acquisition, first-run cues, because they are intense, acquire a strong capacity to signal reard. First-run cues are present only on the first run of a series of massed extinction trials and therefore undergo little extinction. Thus, their reintroduction folloing a long temporal interval leads to elevated responding, so-called spontaneous recovery. But notice that the reasoning used in connection ith first-run cues applies ith little modification to the change in alley brightness experienced by Group GP. Thus, the elevation of responding shon by Group OP to a change in alley brightness in extinction is ascribed here to the same general mechanism that produces so-called spontaneous recovery, ith the introduction of a cue in extinction-a change in alley brightness-itselfhad undergone little extinction-being present on a fe extinction trials-but hich had acquired in acquisition a strong tendency to signal reard. The present results suggest that the overshadoing of memory cues by phrasing cues may, in certain instances, be mistaken for forgetting. Generally speaking, the failure of some prior event to influence current performance is usually attributed to forgetting that event. But it as found here that O-pellet cues failed to become a signal for reard not because of forgetting, but because of overshadoing. Overshadoing of memory cues has not been emphasized in memory experiments. Thus, the possibility arises that in other experimental situations, effects attributed to forgetting may have been due to memory cues' having been overshadoed by phrasing cues. As a relevant specific example, N-R transitions are capable of controlling responding hen as much as 24 h intervenes beteen the N item and the subsequent R item, but the extent of such control seems to decrease as the intervening interval increases (see, e.g., Capaldi, 1967; Jobe, Mellgren, Feinberg, Littlejohn, & Rigby, 1977). One interpretation of this is in terms of increased forgetting of the O-pellet item ith the passage of time. Another possibility, the one being emphasized here, is that forgetting may be minimal, but that at relatively long intervals O-pellet cues are overshadoed by highly salient first-run cues. Clearly, overshadoing, like forgetting, suggests decreased behavioral control by O-pellet cues at long intervals, but for entirely different reasons. As may be seen, hoever, overshadoing has the advantage of consistency in connection ith the present findings. That is, e have ascribed the reduced behavioral control exercised by O-pellet cues at short intervals (Group GP in Experiment 1 and Group B-B in Experiment 2) and at long intervals (Group T-T in Experiment 2) to the same factor-overshadoing of O-pellet cues by phrasing cues. The present analysis suggests that there may be a variety of cases in hich the overshadoing of memory cues by phrasing cues has been erroneously ascribed to forgetting. To general suggestions have been made as the most fruitful approach to animal learning. One is that serial learning, including animal serial learning,

13 SERIAL LEARNING 19 is unique and can best be understood ithin the frameork of human cognitive rule-encoding models of serial learning (e.g., Fountain et al., 1984; Hulse, 1978; Hulse & Dorsky, 1977, 1979). The other is that animal serial learning, although unique in certain respects, has much in cornmon ith various more orthodox instrumental learning situations, partial reinforcement, discrimination learning, and the like (e.g., Capaldi & Molina, 1979; Capaldi et al., 1980). The present results are relevant to this issue. Note that commonly, in serial learning investigations, animals trained under one series are shifted to a second series in order to determine hat as learned under the first (e.g., Capaldi et al., 1980; Hulse & Dorsky, 1979; Richardson & Kresch, 1983; Straub & Terrace, 1981). This, of course, as the reason animals ere shifted to an extinction series here-to determine the strength of an interitem association formed in a serial learning task containing N-R transitions. The shift to an extinction series employed here, hoever, has a marked advantage: N-R transitions have been examined in a ide variety of more orthodox instrumental learning situations and ith effects similar to those obtained here. Thus, N-R transitions have been shon to reduce discriminative responding (e.g., Capaldi et al., 1975; Capaldi et al., 1984;Haggbloom, 1980b, 1982), to retard reversal learning in discrimination tasks (e.g., Grosslight & Radlo, 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 reard schedule situations in animals (e.g., Capaldi, 1964, 1967; Leonard, 1969) and people (e.g., Grosslight, Hall, & Murin, 1953). Similarities of the sort noted above support the vie that serial learning, hatever its unique characteristics, may be vieed as continuous ith various more orthodox instrumental learning situations. 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