Hemispheric Lateralization: a Complex and Subtle New Field For Consumer Research

ABSTRACT - This paper discusses three papers concerning hemispheric lateralization. Each of the papers has weak findings but are consistent with the psychology source literature. Possible explanations for the weaknesses are explored and data are presented to show the complex nature of hemispheric lateralization as seen in the author's EEG research.

Citation:

Michael L. Rothschild (1987) ,"Hemispheric Lateralization: a Complex and Subtle New Field For Consumer Research", in NA - Advances in Consumer Research Volume 14, eds. Melanie Wallendorf and Paul Anderson, Provo, UT : Association for Consumer Research, Pages: 54-56.

Advances in Consumer Research Volume 14, 1987      Pages 54-56

HEMISPHERIC LATERALIZATION: A COMPLEX AND SUBTLE NEW FIELD FOR CONSUMER RESEARCH

Michael L. Rothschild, University of Wisconsin

ABSTRACT -

This paper discusses three papers concerning hemispheric lateralization. Each of the papers has weak findings but are consistent with the psychology source literature. Possible explanations for the weaknesses are explored and data are presented to show the complex nature of hemispheric lateralization as seen in the author's EEG research.

INTRODUCTION

A recent trend in consumer research has been toward a greater focus on emotional and nonverbal stimuli and on their processing. One area of study brought to bear on this topic has been that of hemispheric laterality, a topic with rich potential but one of complex issues, theories and methods.

The three papers in this session introduce three different paradigms concerning hemispheric laterality as a way of evaluating stimuli and the cognitive and affective processes that result from exposure to stimuli. There are some commonalities across the three studies that are interesting. Each presents basically accurate introductions of the literature upon which it is based, each reports results that are consistent with that literature, each has insights and ideas useful to consumer researchers and each obtains results that are weaker than its researchers would have liked to see.

This paper discusses possible reasons for this last commonality and presents a summary of the author's work that might be helpful in explaining some problems. The three papers have flaws that need to be examined for two reasons:

1. The subject of hemispheric lateralization is extremely complex; and

2. The results obtained in this area are often weak and subtle.

Flaws in design quickly tend to wipe out effects in such cases.

Complexity of Processing

It is too simple to think of a clean separation of processing between hemispheres in normal subjects. Music and pictures are not processed exclusively in the right hemisphere, and words are not processed exclusively in the left. The EEG literature shows tendencies to process in certain locations but there is rarely more than a 15% processing advantage for either hemisphere; as stimuli become more complex, this differential decreases. Gevins, et al. (1979) do not believe there is any evidence for lateralization of different cognitive functions, but this extreme view seems to be in the minority.

In addition, as shown in Figure 1, there are also anterior-posterior differences such that the frontal lobes have a differential advantage in showing affective processing (frontal left dominance reflects positive affect; frontal right dominance reflects negative affect), while the posterior lobes (occipital, parietal, temporal) are more likely to show cognitive processing. It is important to keep in mind that the anterior-posterior functions may be as important as the hemispheric differences. A good summary of frontal activation can be found in Davidson (1984).

Given the complexity of this topic and the subtlety of results, it is important that research be done precisely.

Seemingly minor issues can mask potential findings. The next part of this paper discusses the three papers and examples of such problems.

FIGURE 1

HEMISPHERIC AND ANTERIOR/POSTERIOR PROCESSING DIFFERENCES

COMMENTS REGARDING THE THREE PRESENTED PAPERS

Anand, Holbrook and Stephens (1987)

As with the other papers, this one is interesting but the results are weak. Potential flaws include:

1. There is a lack of pretesting of the stimuli. The research examines differences between text and music stimuli in terms of recognition and affect; in order to do this it would seem necessary to know some things about the stimuli. Was there prior knowledge of the stimuli? While it would be easy to select a previously unseen piece of text, was the music also unknown to the subjects? Was the music soothing and likeable or grating and disliked? Again, it would seem easy to find a neutral piece of text. If there were a test of memory, would both stimuli be equally learnable?

2. The design is not fully balanced. The impact of the first flaw is seen here. To test laterality effects on affect, it would seem proper to examine both positive and negative stimuli. Both stimuli are needed because both reception and affect are lateralized. If reception through the right ear leads to positive affect, is this because the stimulus is initially processed in the left hemisphere (and is therefore closer to the left frontal lobe which is activated to show positive affect), or because the stimulus is positive and would activate the left frontal lobe regardless of how it is received?

3. Gender of respondents was not considered. As discussed by Myers-Levy (1987), hemispheric laterality is gender specific and therefore must be considered in this type of research. It is possible that results would be clearer if separated by Bender.

4. The design does not allow for the assessment of stimulus interaction. If stimuli are exclusively processed in-one hemisphere, then there might be little interaction between stimuli, but if there is parallel processing there could be considerable interaction. The design doesn't allow for assessing interaction, but the (positive) music could interact with the (neutral) text such that the text could be felt to be positive. If the text were received in the left hemisphere without the music in the right hemisphere, it might not be received positively. To eliminate this explanation, the design must include cells that separate music and text stimuli.

Heckler and Childers (1987)

Again, the idea for the paper is interesting, but the results are not as strong as the authors would have liked. There are at least two contributors to the weak findings.

1. Lack of consideration of visual field of verbal and visual stimuli. In most consumer research this is not a relevant consideration, but if the topic of the work is hemispheric lateralization, then visual field is important. Janiszewski (1987) has shown that a stimulus seen in the right visual field is initially received in the left hemisphere. Processing then differs depending on whether the stimulus is verbal or visual.

Heckler and Childers test recall of verbal and visual components of print ads but don't consider the visual field of the stimuli. By neglecting this issue, potential results may be diminished because the visual and verbal components appear randomly in their ads, with no visual field control.

To be precise, research on laterality effects needs to consider and control location of the verbal and visual stimuli, relative size of each, size of the total ad and subject's distance from the ad. Janiszewski attempts to control focal point of vision by asking subjects to read editorial content which has ads to its left and right. This level of control is necessary for studies of laterality.

2. Gender of respondents was not considered. See point 3. above.

As Heckler and Childers report, there is little dominance for complex stimuli, and most individuals are mixed processors. If this is the case, then Anand, Holbrook and Stephens need to strongly consider the possibility of interactions in their dichotomous listening task.

Myers-Levy (1987)

This paper is consistent with the others in that it is properly grounded in the psychology literature from which it is derived. This literature shows that there are clear gender differences in laterality effects and that a priming task can have a strong impact on the outcome of following tasks. This paper, though, also has some flaws that possibly limit the findings.

1. How long does a prime last? In this experiment the length of the priming task, and the interval between the priming task and the experiments task were very loosely controlled. Subjects had five minutes for the priming task, but may have finished sooner or may have not paid attention to the task at some point. The strength of the prime is therefore not clear.

In the EEG literature, evoked response potential methods show a lag of 300 msec between stimulus and response. In our work the average lag is one to 1.5 seconds, and the average attention span is about 5 seconds. Given these short time periods, more control of the prime is necessary.

2. Why doesn't the prime work for the sorting task? There are at least two competing explanations for why there was no effect in this part of the experiment. Perhaps the prime decayed before the sorting task was initiated or perhaps the sorting task was too strong to be effected by the prime. We cannot sort out these explanations because the design is unbalanced; it is necessary to add cells wherein the sorting task precedes the similarity task.

3. Lack of consideration of visual field of verbal and visual stimuli. See point 1. under Heckler and Childers.

As consumer researchers branch out into new fields it is important to appreciate the complexities of these fields. While the three papers in this session introduce interesting ideas to our field, they also show weak findings that are at least in part due to a lack of consideration of the underlying complexities of the source field.

In the remainder of this paper I will try to show some of the complex relationships that we have found concerning laterality and EEG data. The area of EEG is also unforgiving of seemingly minor flaws in method. For example, our work examines EEG responses in half second chunks and shows clear stimulus - response relations; Olson and Ray (1983) used a similar method but aggregated data in two second and five second chunks. EEG changes are so rapid that they smooth out when aggregated over two seconds; therefore only weak results were found by Olson and Ray.

Recent EEG Work By Rothschild, Reeves, Thorson And Hyun

Summary of Method

Two similar studies were conducted; in each case subjects saw half an hour of television programming with nine commercials embedded. The commercials were prejudged to be emotional, rational or mixed; three videotapes were made to balance the order of commercials across the tapes. All subjects were adult right handed women. Data were collected and aggregated every half second from four locations on the scalp (right and left; frontal and occipital) in the alpha frequency range. Data analysis was based on a sixty period EEG time series (60 half seconds) per commercial. Within each commercial ten stimuli were identified (e.g., verbal audio, nonverbal audio, supers, scene change, appearance of package, body movement, head movement, zooms). A complete methods statement can be found in any of our other papers (Reeves, et al., 1985; 1986; Rothschild, et al., 1986a; 1986b).

Summary of Findings

This partial summary is designed to show the complexity of the laterality issue when dealing with a multifaceted stimulus such as a television commercials and does not summarize all of our work to date.

Over the nine commercials and ten stimulus variables there were 90 opportunities for correlations with EEG. Forty of these were significant with right hemisphere EEG, 33 with the left hemisphere. While there is a dominance in the right hemisphere there is parallel processing in the left hemisphere. Television, because it is primarily visual, is felt to be a right hemisphere stimulus. While there is right dominance in general, this is not the case for verbal stimuli or rational commercials (Rothschild, et al., 1986a).

Regression models for each commercial and hemisphere also show parallel processing; in addition, auto-correlation is greater in the left hemisphere, perhaps because the right hemisphere is felt to monitor all incoming stimuli and therefore changes more rapidly (Rothschild, et al., 1986a).

Regression models can also be constructed to examine dominance in one hemisphere relative to the other. These also show complex processing; rational commercials show stronger models for left dominance while emotional commercials show the reverse (Rothschild, et al., 1986a).

In comparing the right and left time series for each commercial, we see significant correlations for the two hemispheres which indicate parallel processing, but a great deal of unexplained variance to allow for dominance (Rothschild, et al., 1986a).

The above findings are from the occipital lobe. In the frontal lobe there are significant correlations that show positive affect being dominant in the left hemisphere while negative affect is dominant in the right (Reeves, et al., 1986).

Several replications and reliability tests have been tone across the two studies; in addition the data are quite consistent with the EEG literature (Rothschild, et al., 1986a).

CONCLUSIONS

These findings are only a small subset of what we have uncovered; they show the enormous complexity of the brain and of studying hemispheric laterality. This point could be made with other EEG data as well, but reflects work with which I as familiar.

The three papers presented in this session are good examples on at least two dimensions. Positively, they show a part of the wide range of topics that can be studied through hemispheric laterality. Negatively, they show the difficulty of deriving strong findings in an area where, at best, findings are weak and where the confounding issues are quite complex.

I am convinced that this area will be a worthwhile one for consumer research to pursue and would encourage more work on the topic. At the same time I would urge extreme care in the design of studies that can so easily yield no results on the basis of seemingly minor oversights.

REFERENCES

Anand, P., Holbrook, M. and D. Stephens (1987), "Lateral Asymmetry of Preference Judgments in a Dichotic Listening Task: In One Ear and in the Other," in P. Anderson and M. Wallendorf (eds.), Association for Consumer Research Proceedings, Volume XIV.

Davidson, R. J. (1984), "Affect, Cognition and Hemispheric Specialization," in C. E. Izard, J. Ragan and R. Zajonc (eds), Emotions, Cognitions and Behavior. New York: Cambridge University Press.

Gevins, A. S., & Zeitlin, G. H., Doyle, J. C., Yingling, C. D., Schaffer, R. E., Callaway, E. and C. L. Yeager (1979), "Electroencephalogram Correlates of Higher Cortical Functions," Science, 203 (February), 665-667.

Heckler, S. E. and T. L. Childers (1987), "Hemispheric Lateralization: The Relationship of Processing Orientation with Judgment and Recall Measures for Print Advertisements," in P. Anderson and M. Wallendorf (eds.), Association for Consumer Research Proceedings, Volume XIV.

Janiszewski, C. (1987), Implications of Hemispheric Organization and Processing on Placing and Developing Print Advertisements. Northwestern University: Unpublished doctoral dissertation.

Myers-Levy, J. (1987), "Gender Differences in Cortical Functioning," in P. Anderson and M. Wallendorf (eds.), Association for Consumer Research Proceedings, Volume XIV.

Olson, J. and W. Ray (1983), "Brain Wave Response to Emotional Versus Attribute Oriented Television Commercials," Cambridge: Marketing Science Institute Working Paper.

Reeves, B., Lang, A., Rothschild, M. L. and E. Thorson (1986), Emotional Television Scenes and Hemispheric Specialization,-- Madison: University of Wisconsin Working Piper.

Reeves, B., Thorson, E., Rothschild, M. L., McDonald, D., Hirsch, J. E. and R. Goldstein (1985), "Attention to Television: Intrastimulus Effects of Movement and Scene Changes on Alpha Variation Over Time, International Journal of Neuroscience, 27, 3, 241-256.

Rothschild, M. L., Hyun, Y. J., Reeves, B., Thorson, E., Hirsch, J. E. and R. Goldstein (1986a), Replicability and Reliability of Hemispheric Lateralization in EEG," Madison: University of Wisconsin Working Paper.

Rothschild, M. L., Thorson, E., Reeves, B., Hirsch, J. E. and R. Goldstein (1986b), -EEG Activity and the Processing of Television Commercials," Communication Research, 13 (April), 182-220.

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