Top-Down, Stimulus-Based, and Bottom-Up Processes: Implications For Consideration Set Formation in Brand Choice

Citation:

Richard W. Olshavsky (1994) ,"Top-Down, Stimulus-Based, and Bottom-Up Processes: Implications For Consideration Set Formation in Brand Choice", in AP - Asia Pacific Advances in Consumer Research Volume 1, eds. Joseph A. Cote and Siew Meng Leong, Provo, UT : Association for Consumer Research, Pages: 4-9.

Asia Pacific Advances in Consumer Research Volume 1, 1994      Pages 4-9

TOP-DOWN, STIMULUS-BASED, AND BOTTOM-UP PROCESSES: IMPLICATIONS FOR CONSIDERATION SET FORMATION IN BRAND CHOICE

Richard W. Olshavsky, Indiana University

[The author thanks Anand Kumar and Prakash Nedungadi for helpful comments on this paper.]

ABSTRACT -

Several revisions to the existing model of consideration set formation are proposed. The most important revision is to exclude "goal-appropriateness" as a defining feature of the consideration set. While it is recognized that goals may play a crucial role in the formation of the consideration set, many goal-inappropriate alternatives may be accessed in a variety of other ways. Another important revision is to specify some important differences in the consideration set formation process that occurs depending upon which of three approaches to choice is adopted-top-down, stimulus-based, or bottom-up. The existing model of consideration set formation assumes that only the top-down approach occurs.

INTRODUCTION

Consideration sets are currently receiving a great deal of attention (e.g., Ratneshwar and Shocker 1991; Shocker, Ben Akiva, Boccara, and Nedungadi 1991; Nedungadi 1990). The reason for this renewed interest in consideration sets (also known as "evoked sets") is that the composition of the consideration set has important implications for final choice. For example, if a brand has not been included in the consideration set, then it cannot be chosen. The process by which consideration sets are formed, the factors that influence this process, and the effects of consideration set composition on choice have been the primary research topics.

This paper begins with a brief description of three alternative approaches to choice: top-down, stimulus-based, and bottom-up. Then, the existing model of consideration set formation is described. The first purpose of this paper is to demonstrate that researchers in the area of consideration sets assume that consumers adopt a "top-down" approach to brand choice. Yet, there is considerable prior theory and research to suggest that two alternative approaches to choice, namely, "stimulus-based" and "bottom-up" can and do occur. It is argued that when a stimulus-based approach or a bottom-up approach is adopted, consideration sets are not formed in the same manner as occurs for the top-down approach.

A second, perhaps more important, purpose of this paper is to argue that the existing model misspecifies the basic construct of "consideration set" because it restricts membership in the consideration set to goal-appropriate alternatives. A revised set of definitions and relationships are proposed. Then a revised model is presented that incorporates these different definitions and relationships among the basic constructs. The manner in which a consideration set is formed within each of the three approaches to choice (top-down, stimulus-based, and bottom-up) is then described.

Finally, based upon the new definitions and the revised model some implications are presented for future research on the consideration set formation process.

THREE APPROACHES TO BRAND CHOICE

The Top-Down Approach

Top-down processing (Bettman 1979; Johnson 1984; Gutman 1982; Park and Smith 1989) refers to a set of integrated processes that begins with a specification of a consumer's goal (e.g., a desire to take good photographs of the family). (Memory processes are assumed to be involved throughout all of these processes.) Then the positive and negative consequences of this goal are derived (e.g., a desire for good photographs of the family implies a desire for sharp images and a desire to avoid double exposures). Then the attributes of a product/service that are believed to be instrumental in achieving/avoiding these consequences are specified (e.g., automatic focus produces sharp images, automatic advance avoids double exposures). In this manner, the consumer's choice criteria are formed.

At about the same time that the choice criteria are being formed, various types of products/services are accessed from various sources; e.g., several types of 35 mm cameras (e.g., SLR manual, SLR automatic) and "instant" cameras may be retrieved from long term memory or obtained from advertising, friends, visits to retail outlets, product-testing organization's reports, etc. This initial group of products/services may be goal-drived (Barsalou 1983) but it may also include many alternatives that later prove to be inappropriate to the goal. One or more categories in this initial set of alternatives may then be specified further at the level of available brands and models within types (e.g., SLR automatics include Canon EOS A2E and Pentax PZ-1 and "instant" cameras include Polaroid). In this manner, the set of brands/models to be evaluated or the consumer's consideration set is formed.

Next the image of each brand/model within the consideration set is formed. Image refers to the consumer's beliefs about each alternative in the consideration set on each of the choice criteria. Image may be formed by processes such as direct learning, judgment, and inference. For example, a consumer may learn that the Pentax PZ-1 has a shutter speed that ranges from 30 to 1/4000 seconds. In effect the consumer forms a brand-by-attribute matrix with a specific belief for each of the cells of the matrix. (This matrix may be incomplete and erroneous.)

The consumer next selects a choice strategy for evaluating the alternatives within the consideration set. The selection of a choice strategy is assumed to be determined by a consideration of the relative benefits and costs of alternative choice strategies (Payne 1982; Payne, Bettman, and Johnson 1992).

Taken together, the choice criteria, the consideration set, the image of alternatives, and the choice strategy form the consumer's choice space (Newell and Simon 1972). The outcome of the choice process (i.e., a preference for a specific brand) is determined by the interaction that occurs over time between characteristics of the consumer and characteristics of the task environment as the consumer attempts to execute the selected choice strategy. Intentions to buy are determined in large part by preferences but intentions are also influenced by financial and temporal constraints (Olshavsky 1985).

The information that is used by a consumer to form a choice space in this top-down manner is obtained from several sources. It may be retrieved either from the consumer's long term memory or from various "external memory aids" maintained by the consumer. External memory aids refer to all devices used by the consumer to store information about goods in hard copy form (e.g., hand written notes, past issues of product-testing organization's reports, clipped ads, and brochures). Additional sources of information include the "marketplace" (e.g., products available at retailers, in-store displays, brochures, salespeople), the "social environment" (e.g., advertising, friends, mass media), or the "physical environment" (e.g., climate, geography).

The Stimulus-Based Approach

In the top-down approach, the consumer "frames" the choice space. In contrast, in the stimulus-based approach, someone else (e.g., the advertiser, a salesperson, a friend, a product-testing agency) frames the choice space. That is, the consumer relies solely on the stimulus to obtain information. For example, in a comparative ad, the advertiser may present the choice criteria, the consideration set, the image of alternatives, and the choice strategy. Even in a noncomparative ad the advertiser may completely frame the choice space by presenting the choice criteria, the image of the touted brand, the choice strategy, and an image of the other alternatives in the consideration set by alluding to the competition and their attributes (e.g., "With These Important Essentials Most AF SLRs Leave Out," "And Add These Exclusives").

As evidence for stimulus-based choice processsing, most of the empirical research on the effects of advertising assumes that consumers form an attitude toward a brand based upon the information presented in a single ad (e.g., Brown and Stayman 1992; MacInnis and Jaworski 1989). Attitude toward the brand, in turn, is assumed to be the primary basis for the formation of an intention to buy the advertised brand. The stimulus-based approach is also represented in laboratory studies of choice that used the information display board or similar devices (e.g., Lussier and Olshavsky 1979).

The Bottom-Up Approach

Top-down and stimulus-based processing represent two extremes of a continuum. It is possible (and likely) that a "stimulus-based" processor will begin with a source of information such as an ad but then modify the proposed choice criteria, the proposed image of alternatives, the proposed alternative brands, or the proposed choice strategy. Consumers who start in a stimulus-based manner but then embellish the provided information to form a more complex choice space are referred to as "bottom-up" processors. In this case however the embellishments are not goal-derived; e.g., a presented brand simply cues the retrieval of another brand (e.g., Nikon C> Pentax).

Evidence for this type of bottom-up approach to choice is provided by laboratory studies in which consumers are observed to recall alternatives memorized earlier (e.g., Biehal and Chakravarti 1986; Lynch, Marmorstein, and Weigold 1988; Lynch and Srull 1982). Also, the bottom-up approach to choice is represented by laboratory studies that use computer generated displays in an attempt to prevent the stimulus-based choice processes that occur when information display boards are used (e.g., Brucks 1985).

Consumer who start in a stimulus-based manner may also transform information to a higher level of abstraction. For example, if a camera ad presents attribute-level information about "automatic focus" then the consumer may transform this to the benefit level (i.e., automatic focus implies sharp images). Or, if an ad presents benefit-level information about "sharp images" then the consumer may transform this to the level of goals (i.e., sharp images imply "good photographs of the family"). Evidence for this type of bottom-up abstracting process has been presented in Bettman and Sujan (1987), Johnson (1984;1988), MacInnis and Jaworski (1989, Levels 4 & 5), Mick (1992, Levels 3 & 4) and Park and Smith (1989).

HOW CONSIDERATION SETS ARE FORMED-THE EXISTING VIEW

In this section, the way in which researchers currently assume that consideration sets are formed is described. An explicit model of this process and definitions of all of the constructs have been presented by Shocker, et al. (1991, pp. 182-5). See Figure 1. But see Nedungadi (1987) and Nedungadi, Mitchell, and Berger (1993) for other models. In the existing model, the "universal set refers to the totality of all alternatives that could be obtained or purchased by any consumer under any circumstance." The "awareness set (or knowledge set) consists of the subset of items in the universal set of which, for whatever reason, a given consumer is 'aware' (whether they 'come to mind' on a given occasion or not) and which are believed appropriate for the consumer's goal(s) or objectives." The "context" consists of "those items the individual may perceive or encounter in the external decision making context (e.g., brands on the supermarket shelves)."

The "consideration set is purposefully constructed and can be viewed as consisting of those goal-satisfying alternatives salient or accessible on a particular occasion."

The "choice set is defined as the final consideration set, i.e., the set of alternatives considered immediately prior to choice."

As can be seen, this model assumes that consumers adopt a top-down approach. The top-down nature of this model (as opposed to a stimulus-based or bottom-up approach) is made evident by the important role played by goals in the definition and formation of the awareness set and the consideration set.

HOW CONSIDERATION SETS ARE FORMED-THE REVISED MODEL

In this section, a revised model of the way in which a consideration set is defined and formed is presented. See Figure 2. All revisions are described with respect to the existing model. The top-down approach to consideration set formation is considered first; subsequently, the stimulus-based and the bottom-up approaches to consideration set formation are described.

The Top-Down Approach

The Universal Set. No revisions are made to the definition of the universal set.

The Available Set. The first revision is to replace the construct of "Awareness Set" with the construct of "Available Set." The "Available Set" encompasses five distinct sets-the "Available Set in Long Term Memory," the "Available Set in the Marketplace," the "Available Set in External Memory Aids," the "Available Set in the Social Environment," and the "Available Set in the Physical Environment." The "Available Set in Long Term Memory" corresponds to the "Awareness Set" in the existing model. The "Available Set in the Marketplace" corresponds to the "Context" in the existing model. And the "Available Set in External Memory Aids" is a construct not explicitly included in the existing model. To simplify Figure 2, the "Available Set in the Social Environment" and the "Available Set in the Physical Environment" are not explicitly shown or described, but they are implied throughout.

According to the existing model, the "Awareness Set consists of the subset of items in the universal set of which, for whatever reason, a given consumer is "aware" (whether they "come to mind" on a given occasion or not) and which are believed appropriate for the consumer's goal(s) or objectives." In the revised model, the "Available Set in Long Term Memory" consists of the subset of items in the universal set of which the consumer is aware (whether they "come to mind" on a given occasion or not), but the reference to "appropriateness to the goal" is deleted. The defining feature of the "availability set" in the revised model is "availablility" not "availability and appropriateness to the goal." And, in the revised model the available set consists of all alternatives that are available not only from long term memory but also from external memory aids, the marketplace, the social environment and the physical environment.

FIGURE 1

THE EXISTING MODEL OF CONSIDERATION SET FORMATION

Defining the "availability set" in this less restrictive manner provides the important advantage of allowing us to focus our theoretical and empirical research on all processes by which information becomes available. Further, separating the available set into five subsets allows us to study the unique processes by which information becomes available in each of these distinctly different subsets. In the case of long term memory, it is learning processes. In the case of the marketplace and the social environment, it is private and public policy making (e.g., a marketing manager's advertising or distribution decisions). And, in the case of external memory aids, it is the consumer's strategy for obtaining and storing information about goods in hard copy form (e.g., a consumer's decision to store past issues of Consumers Report).

The Consideration Set or Accessible Set. In the existing model, "a consideration set is purposefully constructed and can be viewed as consisting of those goal-satisfying alternatives salient or accessible on a particular occasion." In the revised model, a consideration set is purposefully constructed and can be viewed as consisting of those alternatives accessible on a particular occasion. The defining feature of the "consideration set" is "accessibility" not "accessibility and appropriateness to the goal." And, in the revised model the consideration set consists of all alternatives that are accessible not only from long term memory but also from external memory aids, the marketplace, the social environment and the physical environment.

Defining the "consideration set" in this less restrictive manner provides the important advantage of allowing us to focus our theoretical and empirical research on all processes by which alternatives become accessible. Another important advantage is that the distinct types of processes that determine "accessibility" from each of the three types of sources can be studied separately. In the case of LTM, it is retrieval processes. In the case of external memory aids, it is the manner in which information is accessed from a personal "library" (e.g., searching for and reading past stored issues of Consumer Reports). In the case of the marketplace, it is the manner in which information is obtained from various marketplace sources (e.g., direct inspection of products, talking with salespeople, reading packaging). And, in the case of the social environment it is the manner in which information is obtained from ads (and from friends and mass media).

Choice Set Deleted. The last revision is to delete the "choice set" construct. In the existing model the only difference between a "consideration set" and a "choice set" is the size (the consideration set is larger) and the proximity (the choice set is closer) to final choice. The main advantage of this revision is that it serves to emphasize that after the consideration set is formed, only choice processes occur (e.g., phased choice strategies).

FIGURE 2

A REVISED MODEL OF CONSIDERATION SET FORMATION

Because goals may affect the accessibility of alternatives, the revised model captures the top-down approach to choice. And, as with the existing model, the sequencing shown does not prevent the availability set and the accessiblity set from forming simultaneously or interactively. Further, experience can affect the composition of the sets (e.g., available brands may become more accessible with use) but it is assumed that such "learning" feeds forward to future states of the consumer and therefore a feedback loop is not shown in Figure 2.

The Stimulus-Based Approach

Importantly, in the revised model, the consideration set may not always be formed in the top-down manner just described. If the consumer adopts a stimulus-based approach to brand choice, the consideration set may be completely determined by the alternatives presented in a single source. For example, if five alternatives are available within a particular retail outlet and if each of these alternatives can be attended to and perceived, then there may be (at most) five alternatives in the consideration set. It is important to note that in this stimulus-based approach, alternatives from the "Available Set in External Memory Aids" or the "Available Set in Long Term Memory" are either not available or they are available but they are not accessed for some reason; e.g., interference due to part-list cuing (Keller 1991) or failure to bring one's copy of Consumer Reports along on a shopping trip.

The Bottom-Up Approach

In the revised model, a third way in which consideration sets may be formed involves the bottom-up approach. In the bottom-up approach, the formation of the consideration set is assumed to be initiated by the information presented in a single source. But, in addition, alternatives may be accessed from the "Available Set in External Memory Aids" and/or the "Available Set in Long Term Memory." For example, a consumer within a particular retail outlet that displays five alternatives can supplement this set of five with additional alternatives retrieved from long term memory (Bettman 1979; Lynch and Srull 1982). In this case, additional alternatives are retrieved simply because they have been cued by the alternatives present in the marketplace. This process differs from the top-down process in that a high level goal, such as a desire to take good photographs of the family, does not get evoked and therefore does not serve as a cue for accessing goal-appropriate alternatives (Barsalou 1983).

DISCUSSION

Revisions to the existing model have been proposed primarily because the definitions provided for the major constructs in the existing model confuse the role of goals in determining the availability, accessibility, and evaluation of alternatives. The most serious definitional problem arises because "goal-appropriateness" is used as a defining feature of the consideration set. In the revised model the consideration set is defined without reference to goal-appropriateness. It is recognized that when consumers adopt a top-down approach to choice goals may play a crucial role in the formation of the consideration set. If the relevant available subset is long term memory, then goals serve as retrieval cues to access goal-appropriate alternatives (i.e., cued recall). But, alternatives may also be accessed from long term memory that have not been cued by goals. For example, alternatives may be made accessible by priming, by direct associations (e.g., among brands), by indirect associations, by higher order category cues, by incidental cues, or by affectional associations (Bettman 1979; Biehal and Chakravardi 1986; Keller 1991; Lynch, Marmorstein, and Weigold 1988; Lynch and Srull 1982; Nedungadi 1990; Tulving and Pearlstone 1966). Consequently, many of the accessed alternatives may not be goal-appropriate. And, if the relevant available subset is the marketplace or the external memory aids, then it is recognized that goals may play a crucial role in directing attention to various alternatives. But here too, alternatives may be accessed that have not been guided by goals. For example, alternatives may be made accessible by personal selling, by shelf displays, by sampling, or by a product-testing organization's report. The main point is that the consideration set may be considerably larger than the set of alternatives that is cued by the goal and that many of these alternatives may not be "goal-appropriate."

Consider the following example. In the existing model, the consideration set for a consumer who desires a car that has front-wheel drive (i.e., the goal) would consist of all front-wheel drive cars that the consumer is capable of accessing (i.e., excluding cars with rear-wheel drive and four-wheel drive). But if alternatives are accessed in a variety of ways, as is proposed here, then alternatives that are not front-wheel drive (i.e., rear-drive and four-wheel drive cars) may also be accessed. And since many different types of cars are accessed, the front-wheel drive criterion has to be used again (during choice) to eliminate these accessed but goal-inappropriate alternatives. This example demonstrates that in the top-down approach to choice, goals play at least two important but separate roles-1) they contribute to the formation of the consideration set (i.e., retrieval and attentional processes) and 2) they are used in the evaluation of alternatives within the consideration set (i.e., choice processes). One important line of future research then concerns how goals and other factors combine to access alternatives from the five available subsets to form the consideration set.

Given these observations about the definitional inadequacies of the existing model, it becomes evident that past research on consideration sets and their effects on choice must be interpreted very cautiously. For example, Ratneshwar and Shocker (1991) reported (study 3) that "subjects (undergraduates) evoked significantly different product (snack foods) alternatives in different usage contexts ..." Since consideration sets can, by the definition adopted here, be affected by goals or goal-usage situation combinations and by other factors, the important question in future research on the impact of usage context on choice should be the accessibility of various foods under various conditions. Only then can the true impact of usage context on choice be known. For undergraduates and snack foods (i.e., consumers with a highly familiar product category), the results largely reflect what socialization processes and past choice processes have actually produced over time and not what could occur under the right conditions of accessibility (something that marketers are much more interested in knowing). A good example of the type of research being called for here is provided by Nedungadi (1990); he investigated the effect of increasing the accessibility of alternatives on choice by priming certain alternatives. It is likely that several other types of manipulations of the marketplace (e.g., samples, package designs, shelf displays) or manipulations of the social environment (e.g., creative advertising) may also induce consumers to access certain alternatives that otherwise would not be accessed for a particular usage condition.

Revisions to the existing model have also been proposed because the existing model only explicitly recognizes the top-down approach to brand choice. It was argued that current theory and research on choice demonstrate that consumers can and do adopt one of three possible approaches to choice-top-down, stimulus-based, and bottom-up. The processes that precede brand choice "frame" the choice space in critical ways; here the focus has been on the size and composition of the consideration set. From a practical perspective this means that the same marketing variable (e.g., an ad, an in-store display) can have quite different effects on brand choice because some consumers adopt the top-down approach, some adopt the stimulus-based approach, and some adopt the bottom-up approach and each of these three approaches may imply substantially different consideration sets.

Olshavsky and Kumar (1993) suggested that the approach consumers take to brand choice is determined by factors such as involvement and prior knowledge. If so, then systematic changes should be observable in future empirical studies that manipulate or measure these variables. If for example, high knowledge, high involvement consumers engage in a top-down approach then their choice process may involve a very different consideration set than low knowledge, low involvement consumers who are more likely to adopt a stimulus-based or bottom-up approach. More research is required to identify other factors that determine which approach to choice consumers adopt.

For a comprehensive understanding of consideration sets, the revised model suggests that we should also study the effect of the "available set" on the "consideration set." It is extremely important to know how alternatives becomes available in long term memory. Learning, for instance, is a much neglected area of research (Shimp, Stuart, and Engle 1991). Important shifts in market share may result from significant changes in the availability (and hence the accessibility) of alternatives in long term memory produced by factors such as an unusually effective product design. And, we know practically nothing about the number and types of external memory aids consumers use. Increases in availability within this source may result from increases in involvement or from the provision of the right types of memory aids in hard copy form (e.g., visible logos on clothing).

Finally, it is important that we also study the impact of changes in the composition of the "universal set" on changes in the consideration set. For example, important changes in market share have occurred (and are likely to occur in the future) because technological advances have produced major changes in the composition of the universal set.

REFERENCES

Barsalou, Lawrence W. (1983), "Ad Hoc Categories," Memory and Cognition, 11(3), 211-227.

Biehal, Gabriel and Dipankar Chakravarti (1986), "Consumers Use of Memory and External Information in Choice: Macro and Micro Perspectives," Journal of Consumer Research, 12 (March), 382-405.

Brown, Steven P. and Douglas M. Stayman (1992), "Antecedents and Consequences of Attitude toward the Ad: A Meta Analysis," Journal of Consumer Research, (June), 34-51.

Brucks, M. (1985), "The Effects of Product Class Knowledge on Information Search Behavior," Journal of Consumer Research, 12 (June), 1-16.

Gutman, Jonathan (1982), "A Means-End Chain Model Based on Consumer Categorization Processes," Journal of Marketing, 46 (Spring), 60-72.

Johnson, Michael D. (1984), "Consumer Choice Strategies for Comparing Noncomparable Alternatives," Journal of Consumer Research, 11 (December), 741-53.

Keller, Kevin Lane (1991), "Cue Compatability and Framing in Advertising," Journal of Marketing Research," 28 (February), 42-57.

Lussier, Denis A. and Richard W. Olshavsky (1979), "Task Complexity and Contigent Processing in Brand Choice," Journal of Consumer Research, 6 (September), 154-165.

Lynch, John G., Jr. and Thomas Srull (1982), "Memory and Attentional Factors in Consumer Choice: Concepts and Research Methods," Journal of Consumer Research, 9 (June), 18-37.

MacInnis, Deborah J. and Bernard J. Jaworski (1989), "Information Processing from Advertisements: Toward an Integrated Framework," Journal of Marketing, 53 (October), 1-23.

Mick, David Glen (1992), "Levels of Subjective Comprehension in Advertising Processing and Their Relations to Ad Perceptions, Attitudes, and Memory," Journal of Consumer Research, 18 (March), 411-424.

Nedungadi, Prakash (1987), Formation and Use of Consideration Set: Implications for Marketing and Research on Consumer Choice, Unpublished doctoral dissertation, University of Florida, Gainesville.

Nedungadi, Prakash (1990), "Recall and Consumer Consideration Sets: Influencing Choice Without Altering Brand Evaluations," Journal of Consumer Research, 17 (December), 245-253.

Nedungadi, Prakash, Andrew A. Mitchell, and Ida E. Berger (1993), "A Framework for Understanding the Effects of Advertising Exposure on Choice," in Andrew A. Mitchell (ed.), Advertising Exposure, Memory, and Choice, Lawrence Erlbaum Associates, Hillsdale, N.J., pp. 89-116.

Newell, A. and H. A. Simon (1972), Human Problem Solving, Englewood Cliffs, NJ: Prentice-Hall.

Olshavsky, Richard W. (1985), "Toward a Comprehensive Theory of Choice," in HIrschman, Elizabeth and Morris B. Holbrook (eds), Advances in Consumer Research, Association for Consumer Research, 12, Provo, Utah: 465-470.

Olshavsky, Richard W. and Anand Kumar (1993), "Top-Down vs. Bottom-Up Processes: Some Implications for the Study of Brand Choice, Proceedings of the Society for Consumer Psychology, American Psychological Association, eds, Karen Finlay, Andrew A. Mitchell, and F.C. Cummins,170-175.

Payne, John W., James R. Bettman, and Eric J. Johnson (1992), "Behavior Decision Research: A Constructive Processing Perspective," Annual Review of Psychology, 43, 87-131.

Payne, John W. (1982), "Continent Decision Behavior," Psychological Bulletin, 92, 382-402.

Park, C. Whan and Daniel C. Smith (1989), "Product-Level Choice: A Top-Down or Bottom-Up Process," Journal of Consumer Research, 16 (December), 289-299.

Ratneshwar, S. and Allan D. Shocker (1991), "Substitution in Use and the Role of Usage Context in Product Category Structures," Journal of Marketing Research, 28 (August), 281-95.

Shimp, Terence A, Elnora W. Stuart, and Randall Engle (1991), "A Program of Classical Conditioning Experiments Testing Variations in Conditioned Stimulus and Contents," Journal of Consumer Research, 18 (June), 1-12.

Shocker, Allan D., Ben-Akiva, Bruno Boccara, Prakash Nedungadi (1991), "Consideration Set Influences on Consumer Decision-Making and Choice: Issues, Models, and Suggestions," Marketing Letters, 2:3, 181-197.

Tulving, Endel and Zena Pearlstone (1966), "Availability versus Accessibility of Information in Memory for Words," Journal of Verbal Learning and Verbal Behavior, 5, 381-91.

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