Bulletin of the Psychonomic Society1984, 22 (5), 409-412

A comparison of forgetting rates infrequency discrimination and recognition

DOUGLAS L. HINTZMANUniversity ofOregon, Eugene, Oregon

and

LEONARP D. STERNEastern Washington University, Cheney, Washington

In two experiments on memory for pictures, a frequency-discrimination task was used to de­termine whether recognition decisions display slower forgetting than do discriminations amongfrequencies greater than O. Experiment 1 compared frequency discriminations of 1-0 (recogni­tion), 2-1, 4-1, and 4-2 and tested retention over an interval of 1 week. Experiment 2 addedanother recognition condition (2-0) and extended retention to 2 weeks. Neither experimentshowed evidence for differential forgetting. The outcome is consistent with the hypothesis thatthe information underlying recognition memory and memory for frequency is qualitatively thesame.

Are judgments of presentation frequency and judg­ments of recognition memory based on the same kind ofremembered information? Intuitively , it seems theymay not be-especially if the to-be-remembered itemswere initially unfamiliar. With such materials, a recogni­tion judgment could be based simply on the feeling thatthe test item is familiar , whereas an accurate frequencyjudgment seems to require access to information of amore specific and qualititatively different kind . We areconcerned here with the question of whether a qualita­tive difference in the kind of information underlyingthese two tasks might be reflected in forgetting rates .Specifically, this study contrasts two hypotheses :(I) that forgetting is slower in recognition memorythan in memory for frequency, and (2) that the twoforgetting rates are the same.

Some theoretical flesh might be put on the firsthypothesis by invoking the distinction between genericmemory-for abstract, general knowledge-and episodicmemory-for specific, autobiographical experiences. Thisbasic distinction has been made under various labels bya number of authors (see Hermann, 1982). Memoryfor frequency , like that for other details of presentation(e .g., modality, context, recency) is inherently episodic .On the other hand, a feeling of familiarity, in the absenceof awareness of such details, could be considered areflection of generic memory. If information in episodicmemory is more easily lost than that in generic memory ,as Tulving (1972, 1983) suggested, then the forgettingrate shown by a particular task should depend on the

This material is based upon work supported by the NationalScience Foundation under Grant BNS-7824987. Requests forreprints should be sent to Douglas L. Hintzman, Department ofPsychology, University of Oregon, Eugene, OR 97403.

relative weights given by that task to generic and epi­sodic information . Thus, if recognition memory reliesmore on the general feeling of familiarity and less onepisodic information than does memory for frequency,then recognition performance should display slowerforgetting than is shown by frequency discrimination.1

One can frame essentially the same argument in termsof types and tokens (cf. Anderson & Bower, 1973).Suppose the first presentation of an unfamiliar itemestablishes in memory both a type node (to representthe item) and a token node (to stand for that particularoccurrence of the item), and that subsequent repetitionssimply create additional token nodes. Finding either atype node or a token node in memory should be suf­ficient for recognition; but accurate memory for fre­quency requires retrieval of tokens. Obviously, in thisspecial case, the type-token distinction correspondsto the generic-episodic distinction, and if one assumesin addition that type nodes are more resistant to for­getting than are token nodes, then recognition shoulddecay more slowly than memory for frequency .

Theoretical support for the second hypothesis-thatforgetting rates in the two tasks should be the same-canbe found in Underwood's (1971) proposal that recogni­tion memory is based on the frequency attribute and inthe multiple-trace theory of memory proposed byHintzman (1976; Hintzman, Grandy, & Gold, 1981).A preliminary report of work with a simulation modelof the latter theory can be found in Hintzman (1984).According to this theory, each repetition of an itemdoes essentially the same thing that the first presentationdoes: It establishes its own memory trace. Thus, there isno type-token or generic-episodic distinction ; and thedifference between recognition and frequency discrimi­nation is purely a quantitative one. That is, determining

409 Copyright 1984 Psychonomic Society, Inc.

410 HINTZMAN AND STERN

that something happened at least N times is basicallythe same, whether N is one or greater than one. If theloss of information in the individual traces of an item isindependent of the number of such traces , then (assimulations confirm) the rates of forgetting in recogni­tion and in frequency discrimination should be the same.

Two problems need to be dealt with if forgettingrates are to be compared. The first is that the circum­stances in which subjects study and are tested should beas similar as possible across conditions. This will avoidconfounding the manipulation of interest with otherfactors that might influence forgetting. In the presentstudy, this requirement is easily satisfied, since a test ofrecognition memory is a special case of frequencydiscrimination. In both experiments, a forced-choicefrequency-discrimination task was used , with frequencycomparisons and retention intervals manipulated withinsubjects . The recognition condition was represented bythe 1-0 discrimination in Experiment 1 and by 1-0 and2-0 discriminations in Experiment 2.

The second problem is that the slopes of two for­getting curves falling at different performance levelsshould not be compared directly , because of possibledistortion by floor and ceiling effects . The ideal solu­tion to this problem would be to equate initial levels ofperformance in the two conditions somewhere belowthe ceiling. But this is extremely difficult to do (cf.Underwood, 1954, 1964), and it is often impossiblewithout introducing confoundings with extraneousvariables (e.g., number of learning trials or presentationrate) that could conceivably affect forgetting rate. Theproblem can, however, be dealt with through systematicvariation. That is, one can deliberately vary performancelevel within one or both of the conditions that are to becompared. In this way, two families of forgetting curvesare generated, and (providing the range of variation in atleast one is sufficient), differential forgetting will bereflected in the crossing of the two sets of curves. Themethod of systematic variation is especially well suitedto the present use of the frequency-discrimination task .We were able to choose several frequency comparisonsthat were known, from prior research, to yield immediate­test performance levels both above and below that forrecognition. A slower rate of forgetting in recognitiondecisions should , therefore , be directly observable in thecrossing or convergence of the curves.

There is one experiment in the literature similar tothe two reported here . Underwood, Zimmerman , andFreund (1971) studied forgetting in a frequency-dis­crimination task, using a 7-day retention interval. Selec­tive comparison of conditions in their Table 1 reveals notendency for performance on pairs of frequency>Oitems to decay more rapidly than that on pairs includinga frequency=O item . However, because the stimuli usedby Underwood et al. were familiar words, the result isnot really relevant to the question under considerationhere. It may be supposed that generic memories already

existed for the frequency=O and frequency>O wordsalike , and thus recognition-memory decisions could notdifferentially benefit from a redundant familiarity cue.The crucial feature distinguishing the present experi ­ments from that of Underwood et al. (1971) was thatunfamiliar stimuli (color vacation slides) were used. Withsuch stimuli, frequency=O items should lack bothepisodic and generic information-presumably a neces­sary condition for differential forgetting to occur.

EXPERIMENT I

This experiment used two retention intervals (30 minand 7 days) and four frequency-discrimination condi­tions : 1-0 (the recognition condition), 2-1,4-1, and 4-2 .On the basis of previous research, performance in the1-0 condition was expected to fall below that in the 4-1condition, but above that in the 2-1 and the 4-2 condi­tions on the 30-min test.

MethodDesign. The stimuli were color vacation slides presented at

a 2-sec rate , in a list 160 positions long (two standard KodakCarousel trays) . The first 5 and last 5 positions were occupiedby filler slides. The ISO experim ental items were arranged infive overlapping blocks. Each block contained four frequency=4items, four frequency=2 items , and six frequen cy=1 items.Repetitions were separated by 4 to 7 intervening items; andwithin a block, the ordering of conditions was random . Presenta­tion of th e successive slide trays was synchronized so that therewas no extra intertray delay .

Each subject was given two frequency-discrimination tests :one 30 min after presentation of the list and one 7 days later.The items on the two tests were different. Either test consistedof 20 randomly ordered pairs of pictures , representing fourfrequency discriminations (I-O, 2-1,4-1 , and 4-2) from each ofthe five blocks of the presentation list.

Fou r rotations of items among conditions were achieved by(l) counterbalancing the orderin g of the test lists given at thetwo delays, and (2) constructing two presentation lists in whichthe frequencie s of the pictures that were paired for testing wereinterchanged (e.g., for Test Pair AB, if freq(A) = I and freq(B) =4 in List 1, then freq(A) = 4 and freq(B) = I in List 2). In thisway , four groups of subjects were defined, across which werecounterbalanced both retention interval and the relative fre­quencies of the members of each pair.

Subjects. Seventy-one paid subjects , recruited from theUniversity of Oregon community, were tested . Testing was donein groups of 2 to 9 persons each. Four subject s failed to reappearfor the second session , and their data were dropp ed. The data of7 other randomly selected subjects were also dropped from theanalysis, to equate at IS the number receiving each of the fourrotations of materials.

Procedure. The subjects were told they would see a series ofvacation slides, some of which would be repeated, and that theywere to study the slides for a memory test. The nature of thetest was not revealed. The 160-item list was then presented by aCarousel projector paced by a timer at a 2-see rate . Followingthis, the subjects were told that another experiment would beconducted before the memory test was given, and they spentabout 30 min rating lists of nouns on semantic scales and beingtested on memory for list membership of the nouns . Next, a testsheet for the first frequency-discrim ination test was distributed.On it were 20 numbered "L-R " pairs. The subjects were toldthat, for each of th e pairs of pictures , they were to decide which

FORGETTING RATES IN FREQUENCY DISCRIMINATION AND RECOGNITION 411

100,..-----------------,

50 L....--..L .l--.........J

ResultsCorrect-response percentages are shown in Figure 2,

in which each 1·0 data point represents 1,024 observa­tions and each of the others represents 512 . Again, per­formance in the 1·0 condition fell below that in the 4-1and above that in the 4·2 and the 2·1 conditions : andagain the 1-0 curve was essentially parallel to the othercurves. The 2-0 and 4·} curves were virtually identical.A planned-comparisons ANOVA on the arcsine-trans­formed proportions showed a difference betwe6 Test 1and Test 2 [F(l ,63) = 180.0, P < .00 1] , but the contrastbetween recognition (1·0 and 2-0 combined) and theother three conditions did not interact significantly withdelay [F(l,63) = 0.02] . Thus, the failure of Experi-

MethodDesign. The color slides were presented in a list 320 positions

long (four Carousel trays) . The 288 experimental items occupiedthe middle 72 positions of each slide tray , while the first 4 andlast 4 position s contained filler slides. Altogether, the experi­mental items included 32 frequeney=4 items, 48 frequeney=2items, and 64 frequen ey=I items. The 288 experimental slideswere ordered randoml y with the sole restriction that a givenpicture could not immediately follow itself. Initially, pictureswere assigned to three sets, determined by the number of avail­able slides of each. Sixty -four pictures for which there were atleast five copies were assigned to the 4-2 and 4·1 conditions.These were paired randomly to make 16 pairs in either condi­tion . Another 64 for which ther e were at least thr ee copieswere assigned to the 2-1 and 2-D conditions in a similar manner ;and a final 64 for whieh there were two copies were assigned tothe 1-0 condition, making two "dummy conditions" of 16 pairseach (one condition of 32 pairs) . Four versions of the presenta­tion sequenc e were generated by keep ing the picture pairingsfor the test always the same, but swapping frequency assign­ments within a pair and switching pairs between the two condi­tion assignments (e.g., 4-2 and 4-1) within a set.

As in Experiment I , each subject was given two frequency­discrimination test s. Either test included half of the pairs assignedto each condition-a tot al of 48 randomly ordered picturepairs. The order of the test lists was counterbalanced, yieldinga total of eight groups of subjects (2 test orders x 4 rotations).

Subjects. Eighty-six subjects, serving for extra credit inundergradu ate psychology classes at the University of Oregon,were recruited . Of these , 9 failed to appear for the second ses­sion and I failed to properly follow instru ctions . For purposesof analysis, the data of 12 other randomly selected subject s weredropped to equate (at 8) the number in each of the eight groups.

Procedure. Presentation and testing were done much as inExperiment l. Exceptions were that (l) there were three briefdelays dur ing presentation for slide-tray changes, (2) the inter­val between presentation and the beginning of Test 1 was about4 min, during which subject s filled out self-addressed postcardreminders of the second session, (3) the presentation rate duringtesting was 5 sec per pair, and (4) the interval between the firstand second sessions was 14 days. The postcards were mailed tothe subject s 2 to 3 days before the second session .

and lest length were increased so that the number ofobservations per subject was at least doubled for everycondition. (3) The total number of recognition observa­tions was made the same as the number of frequency>Oobservations. This was done by adding a 2-0 conditionand making the 1-0 condition twice as large as the others.

7 Days

Retention Interval

<l:"------------0

30 Minutes

EXPERIMENT 2

90

60

Since Experiment I led to acceptance of the nullhypothesis, a second experiment was designed to includeseveral modifications intended to improve the potentialfor uncovering the predicted interaction : (I) The reten­tion interval was lengthened to 2 weeks. (2) List length

memb er had occurred more often in the presentation list, and tocircle either L (left) or R (right) accordingly. Test pairs wereshown simultaneously, by two synchronized proje ctors, at an8-sec rate . After the test sequence, the subjects were told toreturn for a session scheduled I week later . The purpose of thesecond session was not specified. During the second session, thesame test procedure was repeated, with the test list that hadnot been used during the first session.

ResultsCorrect-choice percentages in the four discrimination

conditions are shown as a function of retention intervalin Figure 1, in which each data point is based on 300observations. As had been hoped, the method of system­atic variation produced three frequency-discriminationcurves that nicely bracketed that of the 1-0 (recognition)condition. The 1-0 curve did not cross any of the otherthree . Although the slope of the 4·1 curve was slightlygreater than the slopes of the other conditions, theslopes of the 1-0,4-2, and 2-1 curves were virtually thesame. A planned -comparisons ANOVA on arcsine­transformed scores confirmed this observation. Theinteraction between retention interval as one variableand 1-0 versus the other three conditions as the othervariable was not significant [F(l ,59) = 0.04] . Thus , theprediction that the recognition condition would be for­gotten more slowly than the other frequency discrimina­tions was not supported.

Figure 1. Frequency-discrimination forgetting curves, Experi ­ment 1. The 1-0 discrimination (broken line) is the recognitioncondition.

Rentenfion In t ervol

DISCUSSION

Figure 2. Forgetting curves for Experiment 2. Broken linesrepresen t the recognition conditions.

(Manuscript received for publicat ion Apri l 2, 1984 .)

I. Mandler (1980) proposed a specia l role fo r fam iliarity inre cognition memory. But in shar p cont rast to the abo ve argu­ment (and to our intuition ), he assumed tha t the decay offamiliarity is relative ly fast .

2. Som e cau tions are in order for those who might want todr aw conclusio ns from com parisons of th e relat ive levels of th eobtained curves, either between or within Figures 1 and 2.First, pictures were rotated throu gh co ndi tio ns only as appropri­at e to the purpose of the ex peri ments ; th us, the pictur e pairsco ntri buting to all th e curves were no t the same . Second , thesubjects in Experiment I were paid, and this may be on e reasonwhy the longer ret en tion int erval used in Experiment 2 pro­du ced no mo re forgetting th an was fo und in Experiment I.

NOTES

REFERENCES

A NDERSON, J. R., & BOWER, G. H. (1973). Human associativememory. Washington, DC : Winston.

HERMANN, D. J. (1982). The semantic-episodic distinction and thehistory of long-term memory typologies. Bulletin of the Psycho­nomic Society, 20, 207-210.

HINTZMAN, D. L. (1976). Repetition and memory. In G. H.Bower, (Ed .), The psychology of learning and motivation(Vol. 10). New York: AcadernicPress.

HINTZMAN, D. L. (1984). MINERVA 2: A simulation model ofhuman memory. Behavior Research Methods, Instruments, &Computers, 16,96-101.

HINTZMAN, D. L., GRANDY, C. A., & GOLD, E. (1981). Memoryfor frequency: A comparison of two multiple-trace theories.Journal of Experimental Psychology: Human Learning andMemory, 7, 231-240.

MANDLER, G. (1980). Recognizing: The judgment of previous oc­currence. PsychologicalReview, 87, 252-271.

TuLVING, E. (1972). Episodic and semantic memory. In E. Tulving& W. Donaldson (Eds .), Organization of memory. New York:Academic Press.

T ULVING, E. (1983). Elements of episodic memory. Oxford: Ox­ford University Press.

UNDERWOOD, B. J. (1954). Speed of learning and amount retained:A consideration of methodology. Psychological Bulletin, 51,276-282.

UNDERWOOD, B. J . (1964). Degree of learn ing and the measure­men t of forgetting. Journal of VerbalLearning and VerbalBe­havior, 3, 112-129.

UNDERWOOD, B. J. (1971). Recognition memory. In H. H. Kendler& J . T . Spence (Eds .), Essays in neobehaviorism. New York:Appleton-Cen tury-Crofts.

U NDERWOOD, B. J ., ZIMMERMAN, J., & FREUND, J . S . (1971).Retention of frequency information with observations on recog­nition and recall. Journal of Experimental Psychology, 87,149-162.

et al. (197 1), demon str at e th at the loss of frequency inform atio nfrom mem ory is qu ite slow . Further more, the simple pattern ofthe data suggests a simple ex planation. The data are co nsiste ntwit h a theory that assumes th at th e infor mation underlyingjudgme nts of frequency and recognition memo ry is qu alitativelythe same. And the stri kingly par allel forge tting curves suggest ,in addition , tha t fo rgetting rate is independ ent of frequ ency.That is, the increments (or traces) left by suc cessive repet it ionsare all lost at the same rate.

~2-0

...4 - 1

14 Days

ment 1 to reveal differential forgett ing was completelyconfirmed by Experiment 2.2

The basic quest ion of interest here is whether recog nitionju dgments and judgments of relative freq uency are based onqualitatively different kinds of information. To the ex te nt thatthe two hypoth et ical ty pes of information are characterized bydifferent forgetting rat es, the answer appears to be no . Experi­ment 1 produced a visible but statistically unreliable interact ionin th e pred ict ed direct ion ; and even less evidence fo r the pre­dicted interaction was found in the more powerful Ex perime nt 2.

Of co urse, severa l argum ents could be made agains t th iscon clusion : Perh aps retention intervals on the orde r of severalmonth s are necessary for th e difference in fo rgetting rate s toappear; or perhaps gener ic memories, the hyp othetic al sour ce ofth e added familiarity cue in recognition , requ ire several repet i­tio ns to becom e esta blished. Lackin g a well-artic ulate d th eoryof episodic and generic memory and th eir in teraction, however ,suc h ad hoc object ion s are diffi cult to evaluate .

A furthe r possibility is that , by embe dding th e recognitioncondi tio ns in a frequency-discrimina tio n task , we induced in oursubjec ts a stra tegy of ignorin g or not retrieving familiar ityinformation and basing all judgments solely on episodic mem ory .In co unte rargument to thi s objec tion, it may be not ed th at , inExperiment 2, fully half th e test ite ms were old- new pairs, andit seems unlikely th at all subject s would ignore informat ion thatis relevant to recognit ion decisions in such a situation . Fur the r­more, the fo rgett ing rates in both experiments were not particu ­larly fast. Insofar as we can tell, they were abo ut what previou srecognition-memory data wou ld suggest.

Obviou sly, our null result s leave several theoretical quest ionsunanswered. Recognition and frequency decision s may both bebased en tirely on episo dic information , or bo th entirely onfamilia rity, or both on the same mixture of the two ; or, alterna­tively , two qu alitati vely differen t kinds of information , wh osefo rgetting rates are the same, may be involved . Such speculat ionaside , th e present results, togethe r wit h th ose of Underwood

412 HINTZMAN AND STERN

100

90.....\.>'l> 0... ___

t::Cl

8 0'-.l

'l>I:),

~70t::

'l>\.>'-ct

60

5010 Minute s