Release from proactive interference with positive and negative words.
On control trials, the items that comprise the triads include words similar on some dimension across Trials 1-4 and are based on some predetermined dimension (all high-frequency words, all nouns, all verbs, etc). On experimental, or release, trials, information in the three-item triads is the same across the first three trials (as in the control trials) and then this information shifts to some other dimension or characteristic on Trial 4 (e.g., all nouns on trials 1-3, all verbs on Trial four). If the specific dimension or information contained in the triads is spontaneously encoded by subjects, two events occur. First, there is a decrease in recall performance across Trials 1-3, termed buildup of proactive interference. Second, on shift trials (going from Trial 3 to 4), there will be a sudden and significant increase in recall performance, termed release from proactive interference (RPI). This RPI indicates that the information shift from Trial 3 to Trial 4 was sufficient enough in encoding to alter performance. Conversely, the absence of PI release means that there were no significant changes in the encoding dimension.
Although several stimulus types (words, pictures), modalities (auditory, visual), and age groups (infants, young adults) have been tested using the RPI task (Esrov, Hall, & LaFaver, 1974; Reutener & Fang, 1984; Reutener & Graybill, 1978; Tyrrell, Snowman, Beier, & Blanck, 1990), relatively little work has employed the RPI task with emotionally valenced stimuli. A study by Wickens and Clark (1968) is a lone exception.
Wickens and Clark conducted three experiments to determine if words are encoded for short-term memory (STM) storage by the connotative meaning of the extremes of the three dimensions (evaluation, potency, activity) of the Osgood (Osgood, Suci, & Tanenbaum, 1957) semantic differential. Results revealed that words at each end of these various semantic differential scales are homogeneously encoded into STM and, thus, represent a psychological class differing from words at the opposite end of the scales. In short, subjects are apparently encoding verbal materials by some meaning characteristic which is associated with the extreme ends of these three Osgood scales, thereby offering support for the validity of the bipolarity of these various scales.
Finding only one study performed over 30 years ago that employed the RPI task with presumably emotional stimuli is intriguing, especially because there are now several reports in the literature suggesting that emotionally valenced stimuli are encoded and processed at both an unconscious and conscious level (Denny & Hunt, 1992; Richards, French, Johnson, Naparstek, & Williams, 1992; McCabe, 1999; Watkins, Vache, Verney, & Mathews, 1996). The information processing attributes of emotionally valenced stimuli have much relevance to clinical issues with individuals who may be depressed, anxious, or both.
For instance, several models of information processing in these (and other) clinically relevant groups have been proposed that have yielded several major insights and revelations about the specific cognitive mechanisms that operate in these groups. Specifically, Friedman, Thayer, and Borkovev (2000) have indicated how memory biases for disordercongruent information processing relates to the disentanglement of various clinical psychopathologies. Other methodologies have been advanced to investigate the information processing patterns of various psychopathologies, and these have included, but are not limited to, attentional orienting (Bohlin & Kjelberg, 1979), imagery (Bryden & Ley, 1983), cardiovascular (Friedman & Thayer, 1998), Stroop (Moog, Mathews, & Weinman, 1989), and heart rate (Thayer, Friedman, Borkovec, Johnson, & Molina, 2000). Use of the RPI task may complement those studies presently available that report memory biases in information processing in clinical populations by revealing the type and depth of encoding emotionally valenced stimuli. That is, use of the RPI task with studies on emotional processing would result in an increase in knowledge about how emotional semantic attributes of memory are activated and made available for subsequent processing.
Use of the RPI task results in measures of memory encoding which occur without intention or deliberate strategic processing. Additionally, results from RPI studies allow for an index of spontaneous encoding of stimulus attributes in memory. The procedure, most notably the release from PI performance pattern, can also gauge the level of interference experienced by the participant during this spontaneous encoding of information. Few methodologies exist that examine spontaneous encoding of stimulus attributes in memory and, to date, no such studies can be located in the cognition and emotion literature, at least using verbal materials, that have tested this assumption. One study (McDonald & Prkachin, 1990) found that deficits in the spontaneous encoding of negative emotion (using posed facial expressions) and in nonverbal expression are central to the disorder alexthymia. This, however, is the lone exception of a study investigating spontaneous encoding and negative emotion.
Thus, use of the RPI task with emotionally valenced stimuli adds to the list of tasks noted above by allowing for examination of spontaneous encoding of emotionally valenced material. Additionally, simply encoding information into memory does not guarantee the spontaneous use of that information as the situation or setting arises. Use of the RPI task will allow for an examination not only of how information is encoded, but to what extent that emotional information can be spontaneously encoded and used at a later time, if at all.
If the RPI task shows promise with emotionally valenced stimuli, several patterns of behavior should be observed in the present experiment (see also Wickens & Clark, 1968). First, there should be no difference between experimental and control groups across Trials 1-3. Recall performance should decrease across these three trials, indicating a buildup of PI. This is a standard finding in the RPI literature when the initial Trial 1-3 triads contain items that are similar to each other on some dimension (all nouns, all verbs, etc.). Likewise, there should be a difference in recall performance between the experimental and control groups across Trials 3-4. The control group should continue to show a recall performance decrement, or at least no difference, across Trials 3-4. Conversely, the experimental (or shift) group should reveal an increase in recall performance across these same trials which would be indicative of a release from PI. This pattern of behavior is also a classic and robust finding in the RPI literature. These various issues were investigated in the present experiment.
Forty college undergraduates (M age = 21 years) participated for course credit. Twenty were randomly assigned to the control group (10 received all positive words across Trials 1-4 [PPPP], 10 received all negative words across Trials 1-4 [NNNN], while 20 were randomly assigned to the experimental group (10 received PPPN, 10 received NNNP). Gender was not examined as a factor. No other demographic or psychological data were recorded.
Each subject received a 13-page booklet containing pages in the following order: (a) consent form, (b) Trial 1 page, (c) distractor page, (d) Trial 1 recall page, (e) Trial 2 page, (f) Trial 2 distractor page, (g) Trial 2 recall page, (h) Trial 3 page, (i) Trial 3 distractor page, (j) Trial 3 recall page, (k) Trial 4 page, (l) Trial 4 distractor page, (m) Trial 4 recall page. Pages were all 8 X 11.5 in. Word triads were centered on each page, were arranged in a vertical column, and were printed in uppercase letters. Distractor pages consisted of 625 two-digit odd and even numbers and subjects were instructed to cross out all the even numbers or all the odd numbers. Recall pages instructed subjects to recall as many of the three previous words as they could in any order and to write them down. Also, these free recall pages contained instructions that said not to turn the page until the experimenter said it was acceptable to do so.
Triads consisted of words that had been rated as either positive or negative in their emotional valence and were gathered from several sources (Gotlib, McLachlan, & Katz, 1988; Kuiper & Derry, 1982; Mathews, Mogg, May, & Eysenck, 1989). All stimuli were matched as closely as possible on part of speech, number of syllables, number of letters, and word frequency. No other word characteristics were manipulated or identified. The Kucera-Francis (K-F) frequency value for the positive words (M = 3.67, SD = 2.16) did not differ from the K-F value for negative words (M = 3.47, SD = 2.45) t = .24. Number of syllables did not differ for positive (M = 2.53, SD = .83) or negative words (M = 2.53, SD = .99). Finally, number of letters did not differ for the positive (M = 6.93, SD = 1.33) or negative words (M = 7.67, SD = 1.88) t = 1.25. Assignment of positive and negative words to specific triads and specific trials was done completely randomly with the constraint that Trial 4 stimuli were similar for both groups. Additionally, an attempt was made to ensure that each triad occurred equally often on each trial.
The positive words were adorned, amiable, bliss, genial, gratified, jolly, jovial, kindness, merry, playful, prosper, rejoice, sociable, talented, and vivacious. The negative words were blamed, detested, discontented, downcast, forlorn, gloomy, glum, inferior, melancholy, punished, unlucky, unwanted, unworthy, wilted, and withdrawn.
Subjects were tested as a group and received one of four possible test booklets, containing either all positive (P) or negative (N) word triad stimuli (PPPP, NNNN) across Trials 1-4 or booklets in which word triads on Trial 4 switched from a positive word triad to a negative word triad or vice versa (PPPN, NNNP). Following completion of the consent form, the experimenter asked subjects to turn to the Trial 1 page. Time per word was not measured. Subjects were told to read the three words to themselves silently. After 30 seconds, the experimenter asked subjects to turn to the distractor page. Subjects were allowed 2 minutes to work on the distractor page. It should be noted that none of the subjects completed the distractor task page within the 2-min period. After 2 minutes, the experimenter asked subjects to turn to the recall page and subjects had 1 minute to recall as many of the previous three words in any order as they could. This basic procedure was followed across all four trials. The entire experiment lasted no more than 15-20 minutes.
Recall protocols were scored for number of words correct out of three possible (order was not analyzed) and this value (mean number correct) served as the dependent measure for a series of analyses of variance (ANOVAs). Recall intrusions were not scored or analyzed. Table 1 displays recall performance as a function of group (control, experimental) and trial (1-4).
First, PI buildup was examined in a 2 (Group) X 3 (Trials 1-3) mixed ANOVA. No main effect of group was observed, F(1, 38) = .29. However, the main effect for trial was significant, F(2, 76) = 18.68, MSe = .284, p < .01, eta-squared = .33 and revealed that mean recall performance decreased across Trials 1-3. More importantly, there was no Group X Trial interaction (F = .79). Lack of an interaction indicates that both control and experimental groups showed statistically equivalent recall performance across Trials 1-3, and thus, statistically equivalent PI buildup.
Next, a 2 (Group) X 2 (Trials 3-4) mixed ANOVA was performed to examine any release from proactive interference. There was a main effect of group, F(1, 38) = 11.09, MSe = 1.01, p < .04, eta-squared = .23 and a main effect of trial, F(1, 38) = 55.40, MSe = .11, p < .01, eta-squared = .59. These main effects were qualified by a significant Group X Trial interaction, F(1, 38) = 117.21, MSe = .11, p <.01, eta-squared = .76. This interaction revealed that the experimental group displayed significant release across Trials 3-4, t(38) = 6.43, p < .01, whereas the control group did not, t(38) = .96, p > .05.
Using the RPI methodology, a significant release from proactive interference occurred when Trials 3-4 involved a positive to negative or negative to positive valence shift. The present results not only replicate the basic RPI effect (Wickens, 1972), they highlight the relevance of employing a positive/negative stimulus dimension for spontaneous short term memory encoding (see also Wickens & Clark, 1968). Our results indicate that such a stimulus dimension is adequately encoded into memory.
Groups that include patients with clinical depression and anxiety could benefit from use of this task as a means of exploring the underlying cognitive performance in these diverse groups. For instance, and with regard to anxiety, McNally (1995) has proposed that cognitive biases influence the maintenance and etiology of pathological anxiety. Based on this expectation, one would predict an even greater release from PI in high-anxiety individuals compared to low-anxiety individuals or control individuals. Likewise, in the depression literature, the mood-congruent memory (MCM) effect (Watkins et al., 1996) asserts that sad or depressed individuals have a tendency to remember information consistent with their particular mood state. Thus, in the release from PI task, one would expect that sad or depressed individuals, as compared to non-depressed or non-sad individuals, would show greater RPI for words related to depression, especially if they have spontaneously encoded them during the experiment. Although depression and anxiety were not explicitly manipulated or measured in the individuals in the present experiment, future experiments should test the RPI task with these various clinical groups, manipulating the specific type of stimuli (positive, negative, neutral, depression, anxious, etc.).
To summarize, the present results have indicated that positive and negative words show differential RPI, validating Wickens and Clark (1968). When triad content shifted from all positive words to all negative words (and vice versa) going from Trial 3 to Trial 4, a reliable release from PI was observed. No such release was observed when triad content remained constant across Trials 3-4. Future studies should examine clinical groups in an effort to expand this RPI task to these groups as well as to reveal additional information relating to emotional information processing mechanisms in these groups. The RPI task is relatively easy to administer and score and may provide important insight into cognitive and affective information processing mechanisms. In particular, insight would be gained regarding how the various disorders relate to the spontaneous encoding of information in STM and how this encoding affects subsequent performance.
Table 1 Statistics for Words Recalled as Function of Group and Trial Trial Group 1 2 3 4 Experimental M 2.25 2.00 1.40 2.75 SD .64 .65 .75 .55 Control M 2.00 1.90 1.45 1.20 SD .73 .79 .83 .83 Note. Mean number correct is out of three possible.
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F. RICHARD FERRARO and BRENT KING
University of North Dakota
Correspondence may be addressed to F. Richard Ferraro, Department of Psychology, Box 8380, University of North Dakota, Grand Forks, ND 58202-8380. (E-mail: email@example.com).