Effects of encoding instructions on recall and recognition in Korsakoff patients

Neuropsycholog,a. Vol. 19. pp. 43 to 48. C‘ Pergamon Press Ltd.. IYRI Prmted m Great

EFFECTS

0028

393?/81!010043

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OF ENCODING INSTRUCTIONS ON RECALL AND RECOGNITION IN KORSAKOFF PATIENTS JOHN MCDOWALL* Porirua Hospital, Porirua, New Zealand (Rrceiord

28 April

1980)

Abstract--Korsakoffsubjects and alcohohc controls examined words in a word list under one of three encoding instructions: (1) non-semantic, that is, detecting the presence or absence of the letter “e” in each word; (2) semantic, that is, determining whether a word could fit into a particular sentence, or not; and (3) no encoding instructions. Retention was measured by a free recall procedure (Experiment 1) and by a forced choice recognition procedure (Experiment 2). The results support the hypothesis that Korsakoff subjects are able to semantically encode verbal stimuli without specific instructions to do so. KORSAKOFF’S syndrome manifests itself in a profound amnesia, both retrograde and anterograde in nature. Clinical studies and anecdotal information abound on the nature of this syndrome but recently investigators have used experimental techniques in an attempt to clarify the nature of the memory deficit. CERMAK and his associates [l-4] have argued that Korsakoff patients suffer from an impairment in their ability to encode information. In particular, Korsakoff patients are said to be impaired in their ability to encode verbal information to a semantic level, relying instead on physical or phonemic forms of encoding. Experiments with normal subjects have shown that when words are encoded along semantic dimensions, recall and recognition are higher than when words are encoded along physical or phonemic dimensions [5-S]. In a recent paper, CERMAK and REALE [9] using Korsakoff subjects, examined the relationship between the depth to which a word was encoded and its subsequent retention. These authors used a variation of the C~AIK and TULVING [S] procedure in which the particular encoding procedure adopted by the subject is controlled by the nature of the questions asked about each stimulus word prior to its presentation. In the Cermak and Reale study, the stimulus materials used in Experiment 1 were 60 words and prior to the presentation of each word, subjects were asked either; a question about the words physical characteristics (whether the word appeared in upper case letters or not); a question about phonemic characteristics (whether the word rhymed with a given word or not); or a semantic question (whether the word would fit into a particular sentence or not). Each subject was presented with 60 questions, including 20 sentence questions, 20 rhyme questions and 20 physical questions. Following the presentation of the word list, all subjects were given an unexpected recognition task. The results revealed no differences in recognition scores for Korsakoff subjects across the different encoding procedures. For a group of alcoholic

*Requests for reprints should be sent to John McDowall. Psychology Department, Porirua Hospital, Private Bag,

Porirua, New Zealand. 43

44

JOHN MCI&WALL

controls, semantic questions resulted in a higher recognition score than both the physical and phonemic questions. Experiment 2 of this study was a slight modification of Experiment 1 using two other forms of semantic questions in order to induce semantic encoding. Again, for Korsakoff subjects no significant differences in recognition scores were found across question types. A third experiment greatly simplified the task requirements of the subjects by presenting them with 12 words (including 4 sentence questions, 4 rhyme questions and 4 physical questions) followed immediately by a 36 item forced choice recognition test. This procedure was repeated using different words until a total of 60 test words were administered. The results of this experiment showed that the Korsakoff patients recognised significantly more sentence words than physical words, no other differences being found. The authors concluded that: “the fact that Korsakoff patients’ recognition memory for verbal information can be affected by the level to which they process that information under certain conditions lends some support to the contention that Korsakoff patients’ anterograde amnesia might stem, in part, from a tendency not to perform semantic analyses of to-be-retained verbal information.” (CERMAK and REALE, 1978, p. 173). Such a conclusion is premature given the design of the experiment. In particular, it lacked the inclusion of a “control” group of Korsakoff subjects, i.e. a group receiving no specific encoding instructions but simply asked to learn the words in preparation for a recall test. According to the semantic encoding deficit hypothesis, such a group should recognise as many words as the groups receiving instructions to encode non-semantically. The failure to include such a control group renders the final results difficult to interpret. MCDOWALL [lo], has provided evidence that suggests Korsakoff subjects are capable of analysing verbal information to a semantic level but that they are impaired in their ability to generate retrieval cues at the time of recall. In a paper which examined the relationship between depth of encoding a word and its subsequent recall, MCDOWALL [lo] showed Korsakoff subjects and alcoholic controls a categorized word list under one of three different encoding instructions: (1) non-semantic, that is, detecting the presence or absence of the letter “e” in each word, (2) semantic, that is, assigning words to their correct taxonomic category, and (3) no encoding instructions. Of particular interest was the finding that, given a standard free recall test, the group of Korsakoff subjects receiving no encoding instructions showed a recall performance similar to the group instructed to encode non-semantically. When category label cues were provided at recall time, however, the group receiving no encoding instructions were able to significantly increase their recall performance unlike the group instructed to encode non-semantically. The finding that providing semantic cues at recall time was effective for the group receiving no encoding instructions suggested that the initial encoding occurred at a semantic level. The preserrt experiment examines the performance of Korsakoff subjects given nonsemantic encoding instructions, semantic encoding instructions, and no encoding instructions measured by both recall and recognition tests. According to the semantic encoding deficit hypothesis, during free recall the group of Korsakoff subjects instructed to encode semantically should obtain higher recall than both the non-semantic encoding group and the group receiving no encoding instructions. For the recognition test procedure the same pattern should emerge. The alternative hypothesis, that Korsakoff subjects do encode semantically without specific instructions to do so, but suffer from an inability to retrieve information without cues, would argue that in a free recall condition, the depth to which subjects were instructed to encode test words would have no effect on recall performance. In

DEPTH

OF PROCESSING

IN KORSAKOFF

PAIIENlS

45

other words all groups should obtain a similar recall score. In the recognition procedure, both the group instructed to encode semantically and the group receiving no encoding instructions should be able to take advantage of the cues provided at test time, and increase their scores relative to the group instructed to encode non-semantically.

EXPERIMENT

1

Suhjucrs. Thirty male patients were drawn from the population of a large psychiatric hospital. Fifteen were diagnosed as Korsakoff patients with alcoholic histories, while the control group consisted of I5 patients diagnosed as chronic alcoholics. All the Korsakoff subjects chosen displayed severe anterograde amnesia. While this was clinically obvious in all cases it was formally assessed by presenting subjects with a list of 20 words, one word at a time, and measuring free recall. The mean number of correct words recalled by the I5 Korsakoff subjects was 2.80 (range I to 5). The mean number of words recalled by the subjects in the alcoholic group was 8.53 (range 6 to 12). Persons were eliminated if during assessment they gave evidence of a global confusional state, and candidates with an intelligence quotient (WAIS verbal) of less than 80 were not considered. The mean IQ ratings for the Korsakoff subjects was 95.47 (range 81-105) and for alcoholic subjects 96.60 (range 86-l I I). The mean age for Korsakotl’ subjects was 55.60 yr (range 49966) and for the alcoholic subjects, 54.73 yr (range 46-67). Subjects within each diagnostic group were randomly assigned to one of three groups classified according to encoding instructions. Srimuli untl procetlurr. Stimulus materials were 20,20 x 12.5 cm white cards with one word printed on each card. The words were drawn from the Battig and Montague (1969) norms and were all high frequency nouns unrelated in terms of taxonomic category. Subjects were tested individually and sat facing the experimenter across a table upon which the cards were presented one at a time. Subjects in the semantic encoding group (S) were asked whether the test word to be shown would fit mto a particular sentence or not. Subjects in the no encoding instruction group (N) were asked to look at the words and to try and remember them, and subjects in the non-semantic instruction group (NS) were asked to detect the presence or absence of the letter “e” in each word. Ten of the words contained the target letter. All subjects were told of the recall test that was to follow. Each card was presented for 3 set and 90 set was allowed for recall.

RESULTS

AND

DISCUSSION

The mean percentage correct recall scores for the two diagnostic groups under the three encoding instructions are shown in Fig. 1. The main effect of diagnostic group was significant, F (1, 24) = 67.95, PO.O5. Between group comparisons showed subjects in the alcoholic group to have higher recall scores than Korsakoff subjects for N instructions, F (2, 24) =26.47, P
46

JOHN MCDOWALL

“’ w_

.-.

Alcoholics

.-.Korsakoffs

80-

NS

FIG. 1. Mean percent

S

N ENCODING

recall for Korsakoff

INSTRUCTIONS

and alcoholic

groups

for three encoding

instructtons

would argue that both the group instructed to semantically encode and the group receiving no encoding instructions would benefit from the provision of semantic cues at recall time. Experiment 2 uses the same encoding instructions as in Experiment 1 and utilises a forced choice recognition procedure to measure retention. EXPERIMENT

2

Subjects. The 30 male subjects who served in Experiment 1were also used as subjects in this experiment. A delay of 3 to 5 weeks was allowed between the two experiments. S~imrli und procedurr. The stimulus matertals were 20 words matched m frequency with the words used in Experiment I. Subjects were again randomly assigned to one of three encoding instructron groups as in Experiment 1, and informed that a retention test would follo\c the presentation of the word list. At the end ofthe 11st presentation subjects were shown 20 cards one at a time, each card containmg a block of three words consisting of the target word and two filler words matched in frequency and taxonomtc category with the target word. The position of the target words was randomized over the 20 cards. and subjects were asked to point to the word that he recognized as having been presented during the test.

RESULTS

AND

DISCUSSION

The mean percentage correct recognition scores for the two diagnostic groups under the three encoding instructions are shown in Fig. 2. The main effect of diagnostic group was significant, F (1,24) =23.55, P 0.05. Multiple comparisons of the recall scores for the Korsakoff subjects across the three encoding instructions showed significant differences between NS and N instructions, F (1,24)== 15.65, P
DEPTH

OF PROCESSING

IN KORSAKOFF

PATIENTS

I NS ENCODING Fit;.

N

S

INSTRUCTIONS

2. Mean percent recognition for KorsakofT and alcoholic groups for three encoding instructions.

The results of this experiment show that when retention is measured by a recognition test, Korsakoff subjects in Group N and Group S obtain significantly higher scores than subjects in the NS Group. This finding supports the hypothesis that subjects in Group N were encoding the stimuli to a semantic level.

GENERAL CERMAK and REALE [9] have argued

DISCUSSION

that Korsakoff patients anterograde amnesia may result, in part, from a failure to encode stimuli to a semantic level. The present experiment does not support this hypothesis. In Experiment 1, the depth to which Korsakoff subjects encoded stimulus words did not significantly affect the retention of those words when retention was measured by a free recall test. In Experiment 2, however, a significant encoding effect was obtained when a recognition test was used. If Korsakoff subjects in the absence of specific encoding instructions (i.e. Group N) were unable to encode stimuli to a sematic level, then their recognition scores in Experiment 2 should have been similar to that of Group NS. Instead they obtained a retention score similar to the group instructed to encode semantically suggesting that Korsakoff subjects are capable of encoding to a semantic level without specific instructions to do so. Finally, this study shows that obtaining significant encoding effects for Korsakoff subjects depends heavily on the nature of the retention test administered. Tests involving minimum retrieval information (e.g. free recall) failed to reveal an encoding effect while those providing such information (e.g. cued recall, recognition tests) displayed such an effect.

JOHN MCDOWALL

48

REFERENCES 1. 2. 3. 4. 5. 6. 7. X. 9. 10.

L. S. and BLITT~RS,N. The role of interference and encoding m the short term memory delicits of Korsakoff patients. Nrurops~c’hologia 10, 89-95, 1972. CFRMAK, L. S. and BUTTERS, N. Information processing deficits of alcoholic Korsakoff patients. Q. ./I Stud. AI~~ohol34, I1 l&l 132, 1973. CERMAK, L. S., BUTTERS, N. and GERRPIN, J. The extent of the verbal encoding ability of Korsakoff patients. Narrropsycho/oqiu 11, 85 -94, 1973. CERMAK, L. S., BUTTERS,N. and MOREIN~S,J. Some analyses ofthe verbal encoding deiicit ofalcoholic Korsakoff patients, Bruin Ltq. 1, 141 150, 1974. CRAW, F. I. M. and T~ILVING, E. Depth of processing and the retention of words in episodic memory. J. c’rp. PIN+IO/.. Genrrul 104, 268-294, 1975. FISHER. R. P., and CRAIK, F. I. M. InteractIon between encoding and retrieval operations in cued recall. J. cup. Psycho/.: Hum. Lucrrn. .Mcmory 3, 701_~71I, 1977. Hurx, T. S. Differential effects ofeffort and type of orienting task on recall and organization of highly associated words. J. np. P.~~ckol. 97, 111-113. 1973. HYI~F, T. S. and JENKIYS,J. J. Recall for words as a function of scmantic,graphic, and syntactic orienting tasks. J. wrh. Lcwx. w-h. Behtrc. 12, 471-480. 1973. C~RMAK. L. S. and REAI F,L. Depth of processing and retention of words by alcohohc Korsakoff patients. J. r\-p. P.s~c/d.: Hum. Lrcrrn. Memon 4 (2). I65 174, 197x. MCDOWALL, J. Effects ofencoding instruction and retrieval cueing on recall in Korsakoff patients. Mrm. Cognit. 7 (3). 232 239, 1979. CERMAK,

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