successive contrast effects
TRANSCRIPT
This article was downloaded by: [Central Michigan University]On: 15 October 2014, At: 07:41Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK
The Journal of GeneralPsychologyPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/vgen20
Successive Contrast EffectsDonald T. Williams a & M. Mark Ballenger aa York College of the City University , New York, USAPublished online: 06 Jul 2010.
To cite this article: Donald T. Williams & M. Mark Ballenger (1974) SuccessiveContrast Effects, The Journal of General Psychology, 91:1, 43-50, DOI:10.1080/00221309.1974.9920778
To link to this article: http://dx.doi.org/10.1080/00221309.1974.9920778
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.
This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
The Journal of General Psychology, 1974, 91, 43-50.
SUCCESSIVE CONTRAST EFFECTS*
York College of the City University of New York
DONALD T. WILLIAMS AND M. MARK BALLENGER
SUMMARY
Rat 5s were tested for positive and negative contrast effects with the useof a 2 x 2 design (six or one 45-mg. pellet as reward in pre- or postshiftphase) and with the use of the necesssary methodological controls. Eighty5 s were run in a straight alley for 33 pre- and 10 postshift trials. Asignificant (p < .01) negative contrast effect (NCE) was found, but therewas no evidence of a positive contrast effect (PCE). It was concluded thatthe NCE is a viable behavioral phenomenon, whereas the PCE is questionable.
A. INTRODUCTION
Successive contrast effects were first reported by Crespi (4), who performed a series of experiments to determine the effects of quantitativevariation of reward' on the performance of the white rat. As the result ofbetween-experiment comparisons of running speeds for these 5 s, Crespipointed out that those 5s shifted from a large reward to a small rewardshowed an immediate reduction in performance to a level lower than thatof 5 s originally trained on the small reward. This depression in performance is usually termed a negative contrast effect (NCE). 5s shifted from asmall to a large reward, on the other hand, quickly reached and surpassedthe performance of 5 s originally trained with the large reward. This elationin performance (4, 21) is a positive contrast effect (PC E).
Several investigators (l, 3, 18) have reviewed the contrast effect literature and have found many fewer reports of a PCE than of an NCE.However, there are several generally recognized methodological requirements all of which do not seem to have been met in anyone of the studieson quantitative variation of reward.
.. Received in the Editorial Office, Provincetown, Massachusetts, on May 21, 1973.Copyright, 1974, by The Journal Press.
I The word "reward," in the present paper, simply means the value of the goal stimulus(e.g., the number of pellets), without any connotations about motivation.
43
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
44 JOURNAL OF GENERAL PSYCHOLOGY
One problem is that the 5 s may not have reached a stable level ofperformance, asymptote, prior to being shifted to a different reward.Spence (18) reported three unpublished studies in which an NCE wasdemonstrated but not a PCE. He interpreted the discrepancy betweenthese findings and the classic studies in the area (4, 21) in terms of thenumber of acquisition trials employed. "The findings of these investigationsin which the preshift training was more extensive than that of Crespi andZeaman thus suggest that the elation effect resulted from the fact that theshifts occurred prior to the attainment of the asymptote of performance"(18, p. 132). There is no universal definition of asymptote, and mostexperimenters adopt their own. 5s are generally assumed to have reachedasymptote if they appear to have leveled off in their responding and thereis no days (or trials) effect over that block of trials.
Not all of the contrast studies were designed to test for both NCEs andPCEs (5, 9, 17). Frequently one experimenter finds an NCE in one situation, but another experimenter fails to find a PCE in a different situation.This results in comparisions between experiments rather than within experiments. It follows, then, that a study examining contrast effects per seshould include increased and decreased reward groups.
Another methodological problem arises in transfer experiments whenexperimenters fail to include nonshifted controls (10). The basic paradigmfor investigating contrast effects is to train 5 s on one value of reward andthen to shift them to a second value of reward. For example, one groupmight be trained with a small reward and shifted to a large one. A secondgroup would be trained on a large reward and shifted to a small one. Inthis case all 5 s are shifted and postshift data are compared to extrapolations from preshift data. The proper controls would be groups always runon each reward magnitude so that shifted groups could be compared tononshifted groups at the same point in training. Thus, a group shifted fromsmall to large reward could be compared to a group that received largereward on all trials, and the same would be true for a group shifted fromlarge to small reward.
Similarly, if the variable under examination is reward shift, then othervariables should be kept as constant as possible. For example, if the studyis run 15 trials per day with an intertrial interval (IT!) of five minutes forfive days, then most trials are separated by the five-minute ITI and a fewtrials are separated by an ITI of about 23 hours. As ITI is not the majorvariable under consideration, it would seem reasonable to have the rewardshift occur within the context of the IT! used in the majority of training
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
DONALD T. WILLIAMS AND M. MARK BALLENGER 45
(i.e., five minutes) rather than within the context of an ITI that separatesonly a few trials (i.e., 23 hrs.).
The purpose of the present study was to investigate successive contrasteffects with the use of a design which would permit all of the appropriatemethodological requirements to be met. That is, this study (a) trained all Ssto asymptote before the shift; (b) tested for both NCE and PCE; (c)included nonshifted control groups at both large and small magnitudes ofreward; (d) shifted the reward within the context of the ITI employed inthe majority of training trials.
B. METHOD
1. Subjects
The Ss were naive, white rats, of the Sprague-Dawley strain, whichwere approximately 100 days old. The S s were randomly assigned to fourgroups of 20 Ss each: low preshift and postshift reward magnitude (1-1),high preshift and postshift reward magnitude (6-6), low preshift and highpostshift reward magnitude (1-6), and high preshift and low postshiftreward magnitude (6-1). A criterion of two consecutive failures to enter thegoal box within 100 seconds after Day 2 eliminated five Ss from group 1-1,one from group 6-6, three from group 1-6, and one from 6-1.
2. Apparatus
A Hunter Runway, model 380, with photoelectric cells 10.256 cm (4inches) from the start box and goal box (i.e., 61.538 cm, 2 feet apart) wasused. A Standard Electric timer started when S broke the first photobeamand stopped when S broke the second photobeam, which provided ameasure of latency in the middle 61.538 cm of the runway to .01 second.The Ss were not allowed to re-enter the start box or runway after leavingit. The S s were confined in the goal box for approximately 30 seconds. Thesmall reward magnitude was one Noyes pellet (45 mg.), and the largereward six Noyes peIIets.
3. Procedure
Ss were housed separately in home cages with water always available. A12 gm per day diet was used for two weeks prior to the experiment. S swere also handled every day for approximately two minutes, for one week.One hour after an experimental day's trials Ss were fed 12 gm minus theamount of food received in the alley.
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
46 JOURNAL OF GENERAL PSYCHOLOGY
Forty-three trials were run over a five-day period: three on Day 1, fiveon Days 2 and 3, and 15 on Days 4 and 5. 5s were run in squads of four,one 5 from each experimental group. In order to control for any olfactorycues (cf. 13) each 5 received its daily trials in random order with the otherthree 5 s in its squad. For example, 5 1 received its first trial, 5 3 receivedits first trial, 5 4 received its first trial, 5 2 received its first trial, 5 3received its second trial, 5 2 received its second trial. Therefore, theintertrial interval within days varied around four minutes. The intertrialinterval between days was about 23 hours.
On the first four days and the first four trials of Day 5, 5 s receivedappropriate preshift reward magnitude. On the last 11 trials of Day 5, 5sreceived appropriate postshift reward magnitude.
C. RESULTS
A log transformation (X = Log io 100X) was performed on all of thelatencies before any analyses were performed. An analysis of variance (20)of the last 10 preshift trials resulted in a negligible trials effect (F = 1.96;df = 4,264; P < .1), indicating that the 5s were at asymptote before theshift was made. The data for the last 10 preshift trials and the postshifttrials (trials 24 to 33 and 34 to 43 respectively) are shown in Figure 1.
A t test between the last 10 preshift trials for the 1-6 and 1-1 groups wasnot significant. Nor was a t test between 6-1 and 6-6 groups. As expected,a t test on groups 1-1 and 1-6 VS. 6-6 and 6-1 for the last 10 trials combinedwas significant (t = 3.30; df = 68; P < .01). Thus, at the terminal phase ofpreshift training the 5 s receiving six pellets were responding faster than the5s receiving one pellet. For informational purposes, t tests were alsoperformed for the same groups for the last five trials of Day 4 (t = 2.44;dj = 68; P < .05), and the first five trials of Day 5 (t = 2.84; df = 68;P < .01). That is, the six-pellet 5s were responding faster than the onepellet 5 s at the end of Day 4 and at the beginning of Day 5 just prior to thereward shift.
As seen in Figure 1, the performance of the 1-6 group did not reach theperformance of the 6-6 group on postshift trials, eliminating the possibilityof a PCE. Comparisons between these two groups for all 10 postshift trialsconbined, the first five postshift trials, and the second five postshift trialsall resulted in nonsignificance, as did trial-by-trial t tests with the exceptionof the first postshift trial which was significant in the direction of thepreshift data (t = 2.20; df = 43; P < .05).
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
DONALD T. WILLIAMS AND M. MARK BALLENGER 47
I , , ! , I , , !
5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10Trials
FIGURE 110 PRESHIFT AND ALL 10 POSTSHIFT TRIALS
10°
><00-:= 9IlO0
~>-uc~ 1.8-'c...:0'"
T2
I I
2 3 4
LAST
Group 1-1 Group 6-1 ..---~Group 6-6 _
Group 1- 6 D----_
A comparison between the 1-1 and 6-1 groups' overall postshift performance did result in a significant NCE (t = 3.3; df = 32; P < .01). Again,for a further general evaluation of the NCE a t test for the last fivepostshift trials was significant (t = 3.06; df = 32; P < .01). A t test for thefirst five postshift trials was not significant. Trial-by-trial t tests showed thesixth, seventh, and eighth postshift trials to have significant differences(i.e., respectively, t = 3.38; df = 32; P < .01; t = 2.56; df = 32; P < .05;t = 2.05; df = 32; P < .05). This apparently slow occurence of the NCEmay have been caused by high variability on the early postshift trials, sincethe difference between the group means was in the expected direction afterthe first postshift trial.
D. DISCUSSION
The results of the present experiment, with a design which permitted theappropriate controls and methodologies to be employed, were that an NCEoccurred and there was no evidence of a PCE. That is, 5 s initially trainedon six pellets responded faster than 5 s trained on one pellet, and 5 s shiftedfrom six to one responded slower in postshift training than 5s receiving one
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
48 JOURNAL OF GENERAL PSYCHOLOGY
pellet in pre- and postshift training. However, the 5 s shifted from one tosix pellets did not respond differently from 5 s receiving six pellets in preand postshift training.
It might be concluded that the Ss shifted from one to six pellets failed toshow a PCE because of a "ceiling effect"-i.e., the six-pellet control 5 swere already responding as rapidly as they could and there was no roomfor the shifted Ss to improve relative to these control 5s (especially since allgroups were trained to asymptote prior to shifting rewards). However,results from other work in our laboratory renders such a conclusion untenable. In a recent paper (19) it was reported that groups trained with one,three, and 12 pellets reached reliably different asymptotes. Subsequently,some of the one-pellet 5 s were shifted to three pellets and some shifted to12 pellets. Neither shift group evidenced a PCE. Most importantly, the12-pellet control 5 s were responding reliably faster than the three-pelletcontrol 5s. There was room for improvement which the 5s shifted fromone to three pellets failed to exhibit. Hence, while the notion of a "ceilingeffect" seems intuitively reasonable, it lacks empirical support.
On the other hand the NCE, in the present study, seems highly reliable.The question that arises is the following: Are there any conditions underwhich it might be expected the NCE would not occur?
A survey of the successive contrast effect literature reveals one study byMetzger, Cotton, and Lewis, (14) which employed each of the controlsdiscussed in the Introduction except the first. That is, they may not haverun all 5s to asymptote before shifting reward magnitude. Unlike thepresent study, they did not find an NCE (a PCE was not obtained in theirstudy either), which may have been the result of not training the 5s toasymptote before the shift, thus confounding the effects of the shift withlevel of training. An alternative explanation of the discrepancy betweenour results and theirs is the differences in ITI employed in the two studies.Metzger et at. (14) used a 24-hour ITI and the present study used afour-minute IT!. Since Spence's (18) reasoning that a failure to run 5s toasymptote before the shift might result in a PCE seems sound and since theMetzger et at. study showed no indication of that effect, it seems reasonable that the difference between the Metzger et at. findings and those of thepresent study lies in the difference in the ITIs employed rather than in thedifference in amount of preshift training. A survey of relevant literatureindicates that the effect of ITI on contrast effects is equivocal. Severalstudies (e.g., 5,6,8, 9, 15) used long ITIs and found an NCE; Huang (12)used a long ITI and failed to find an NCE; several studies (e.g., 11, 16)
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
DONALD T. WILLIAMS AND M. MARK BALLENGER 49
used short ITIs and failed to demonstrate an NCE; and some studies (e.g.,2, 7) used short ITIs and demonstrated an NCE. Of course, the methodology in these studies did not differ in ITI alone. However, the methodologyand overall design of the Metzger et al. (14) study and the present study arevery similar except in the ITI employed. A subsequent study then, usingITI as an independent variable, is indicated to investigate the effect of ITIon the NCE.
It is thus concluded that the present study in demonstrating an NCEwithout a PCE, and employing the proper controls, supports the contention (1, 3, 18) that the NCE is a viable behavioral phenomenon, while thePCE is questionable.
REFERENCES
1. BLACK, R W. Shifts in magnitude of reward and contrast effects in instrumental andselective learning: A reinterpretation. Psycholog. Reu., 1968, 15, 114-126.
2. CAPALDI, E. D. Effect of an initial reward magnitude on subsequent resistance toextinction. J. Exper. Psychol., 1970, 86, 283-287.
3. CAPALDI, E. J. A sequential hypothesis of instrumental learning. In K. W. Spence & J.T. Spence (Eds), The Psychology of Learning and Motivation: Advances in Researchand Theory. New York: Academic Press, 1967.
4. CRESPI, L. P. Quantitative variation in incentive and performance in the white rat.Amer. J. Psychol., 1942, 55,467-517.
5. DILoLLO, V. Runway performance in relation to runway-goal box similarity andchanges in incentive amount. J. Compo & Pbysiol, Psychol., 1964, 58, 327-329.
6. DILoLLO, V., & BEEZ, V. Negative contrast effects as a function of magnitude ofreward decrement. Psychon. Sci., 1962, 9, 99-100.
7. EHRENFREUND, D., & BADIA, P. Response strength as a function of drive level and preand postshift incentive magnitude. J. Exper. Psychol., 1962, 63, 468-471.
8. GLEITMAN, H., & STEINMAN, F. Depression effect as a function of retention intervalbefore and after shift in reward magnitude. J. Compo & Physiol. Psychol., 1964, 51,158-160.
9. GONZALEZ, R. C., GLEITMAN, H., & BITTERMAN, M. E. Some observations on thedepression effect. J. Compo & Physiol. Psychol., 1962, 55, 578-581.
10. HALL, J. F. The Psychology of Learning. Philadelphia & New York: J. B. Lippincott,1966.
11. HOMZIE, M. J., & Ross, L. E. Runway performance following a reduction in theconcentration of a liquid reward. J. Compo & Physiol. Psychol., 1962,55, 1029-1033.
12. HUANG, I. Successive contrast effects as a function of type and magnitude of reward. J.Exper. Psychol., 1969, 82, 64-69.
13. McHoSE, J. H., & Ludvigson, H. W. Differential conditioning with nondifferentialreinforcement. Psychon. Sci., 1966, 6, 485-486.
14. METZGER, R, COTTON, J. W., & LEWIS, D. J. Effect of reinforcement magnitude andof order of presentation of different magnitudes on runway behavior. J. Compo &Physiol, Psychol., 1957,50, 184-188.
15. ROBERTS, W. A. The effects of shifts in magnitude of reward on runway performance inimmature and adult rats. Psychon. Sci., 1966, 5, 37-38.
16. ROSEN, A. J., & ISON, J. R Runway performance following changes in sucrose rewards.Psychon. Sci., 1965, 2, 335-336.
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014
50 JOURNAL OF GENERAL PSYCHOLOGY
17. SCHRIER, A. M. Effects of an upward shift in amount of reinforcer on runway performance of rats. J. Compo & Physiol. Psychol., 1967, 64, 490-492.
18. SPENCE, K. W. Behavior Theory and Conditioning. New Haven: Yale Univ. Press,1956.
19. WILLIAMS, D. T., HOFFMAN, D. L., & SANTURIO, O. D. The ceiling effect: Fact orFiction? Paper presented to the Southeastern Psychological Association meetings, NewOrleans, 1973.
20. WINER, B. ]. Statistical Principles in Experimental Design. New York: McGraw-Hill,1962.
21. ZEAMAN, D. Response latency as a function of the amount of reinforcement. J. Exper.Psychol., 1949, 39, 466-483.
Psychology DepartmentYork College of the City University of New York150-14 Jamaica AvenueJamaica, New York 11432
Dow
nloa
ded
by [
Cen
tral
Mic
higa
n U
nive
rsity
] at
07:
41 1
5 O
ctob
er 2
014