A Revised Product Involvement Inventory: Improved Usability and Validity

Edward F. McQuarrie, Santa Clara University
J. Michael Munson, Santa Clara University
ABSTRACT - Four shortcomings of the Product Involvement Inventory published by Zaichkowsky (1985) are identified: usability, discriminant validity, criterion validity and construct validity. A revised ten-item inventory is shown to overcome these problems while maintaining good reliability. The Revised Product Involvement Inventory contains separate sub-scales that measure two facets of consumer involvement: perceived importance and interest. It maintains most of the strengths of the original PII while offering improved criterion validity.
[ to cite ]:
Edward F. McQuarrie and J. Michael Munson (1992) ,"A Revised Product Involvement Inventory: Improved Usability and Validity", in NA - Advances in Consumer Research Volume 19, eds. John F. Sherry, Jr. and Brian Sternthal, Provo, UT : Association for Consumer Research, Pages: 108-115.

Advances in Consumer Research Volume 19, 1992      Pages 108-115

A REVISED PRODUCT INVOLVEMENT INVENTORY: IMPROVED USABILITY AND VALIDITY

Edward F. McQuarrie, Santa Clara University

J. Michael Munson, Santa Clara University

ABSTRACT -

Four shortcomings of the Product Involvement Inventory published by Zaichkowsky (1985) are identified: usability, discriminant validity, criterion validity and construct validity. A revised ten-item inventory is shown to overcome these problems while maintaining good reliability. The Revised Product Involvement Inventory contains separate sub-scales that measure two facets of consumer involvement: perceived importance and interest. It maintains most of the strengths of the original PII while offering improved criterion validity.

We set out to modify and improve the Product Involvement Inventory (PII) developed by Zaichkowsky (1985). It should be emphasized at the outset that the PII is already a good measure by most standards of construct development. Our effort at modification has the goal of strengthening the PII through shoring up weaknesses and improving usability. The Revised Product Involvement Inventory (RPII) was developed to remedy four problems with the original measure: 1) difficulty and impractibility of use; 2) uncertain discriminant validity; 3) limited criterion validity; and 4) an overly narrow conceptualization of involvement.

Usability

The PII can be criticized for its polysyllabic vocabulary and its length (20 item pairs). The level of vocabulary (e.g.,"mundane," "superfluous") may limit the applicability of the PII outside a university environment. Length becomes a problem when a researcher seeks to examine multiple products within a single study. Since earlier multi-item involvement measures had all been product specific (Bloch 1981; Tigert, Ring and King 1976), a key advantage of the PII is its suitability to comparing involvement across diverse products. Yet, the twenty item pairs in the PII, when applied across half a dozen products, might unduly fatigue respondents, making it difficult to measure other theoretical constructs of interest. A decisively shorter PII would have wider applicability while simultaneously offering greater convenience to both respondents and researchers.

Discriminant Validity

An examination of the content of the PII alerted us to a potential problem with discriminant validity. While there are some items in the PII that appear verbatim in commonly accepted scholarly definitions of involvement, such as "relevant" (Krugman 1965); "important" (Hupfer and Gardner 1971); and "interesting" (Mitchell 1979), the PII also includes items such as "valuable-worthless." These terms have a very different provenance: for over thirty years they have been shown to be among the best items for measuring the evaluation component of the meaning of an object (Osgood, Suci and Tannenbaum, 1957, p. 190). Other items found in the PII which have been used to measure evaluation of an object include "useful" and "needed" (Osgood 1969), and "beneficial" (Burnkrant and Page 1982). Closely related in meaning -- although we could not find examples of their use -- are the terms "desirable" and "wanted." Thus, it would appear that between 20% and 30% of the content of the PII represents scale items whose typical use in the social sciences has been to measure a person's favorable or unfavorable evaluation of an object, and not involvement per se.

Inclusion of evaluative terms may confound the measurement of involvement with that of attitude. Hence, a measure of involvement ought to go to some length to exclude items which are predominantly evaluative in nature.

Criterion Validity

Behavioral criteria. Zaichkowsky (1985, pp. 346ff) specified five self-reported criterion behaviors as part of her validation efforts. Recent advances in the literature, however, cast doubt on the adequacy of the behavioral criteria used by Zaichkowsky. An examination of these five criteria (see Table 1) shows that they fall into two groups: three items are concerned with intensified information search or prolonged information processing, and the remaining two are concerned with commitment to a specific brand. Peter and Olson (1987) have argued persuasively that product involvement should be distinguished from brand involvement (cf. Rossiter and Percy 1987). An individual can be involved with the product category without seeing many differences between brands or having a preferred brand. This observation thus compromises two of Zaichkowsky's five items. Regarding the other three criteria, Zaichkowsky herself noted problems with the phrasing of the "reading about" information search measure (p. 347). Therefore, it would appear that the predictive validity of the twenty item PII rests on exactly two self-report items.

The non-brand related criteria used by Zaichkowsky (1985) measure the extent of information search and information processing -- activities that have continued to be judged in the literature as key concomitants of heightened consumer involvement (Beatty and Smith 1987; Bloch et al. 1986; Gensch and Jivalgi 1987). Information search can be indexed by activities such as reading about the product, attending to ads for it and discussing it with other people. Information processing can be indexed by activities such as comparing product characteristics, examining many factors for their potential relevance to purchase, and investing more time in the decision process. Any revision of the PII should have a demonstrated capacity to predict a wide range of such behaviors, and should be highly predictive of a composite measure composed of multiple outcomes.

Situational discrimination. A second approach that Zaichkowsky used to establish criterion validity for the PII was to demonstrate its capacity to discriminate among products and among situations. The claim that the PII discriminates among situations is interesting but problematic. Zaichkowsky (1985) does not indicate whether the PII is intended to measure enduring involvement, situational involvement, or both (Houston and Rothschild 1978). Some authors would argue that different measures are required to assess these two types of involvement (Bloch and Richins 1983; Richins and Bloch 1986). On the other hand, the concept of felt involvement has been introduced by Peter and Olson (1987) to capture the net involvement produced in an individual by both enduring and situational factors. The tests reported in Zaichkowsky (1985) suggest that she intended the PII to be a measure of felt involvement. The support shown for this application of the PII, however, is modest: successful discrimination using one product (red wine) across one situational difference (private vs. socially visible consumption). Use of the PII to measure differences in felt involvement across situations could be better supported through an examination of multiple products across multiple types of situations.

Construct Validity

Theoretical definition of the involvement construct continues to be a contentious area. Clearly, allegiance to one or another theoretical position is going to have marked effects on how one measures the construct. While it is not our intent to present any new theories of involvement, we saw an opportunity to broaden the conceptualization that underlies the PII. Specifically, Zaichkowsky (1985) presents the PII as a measure of a single thing: involvement conceptualized as personal relevance. This is perhaps the most striking difference between the PII and the Involvement Profile developed by Laurent and Kapferer (1985). They insist that a measure of involvement must take into account multiple dimensions to be complete, and succeed in demonstrating the presence of at least four distinct factors in the analysis of their twenty item inventory.

The Laurent and Kapferer measure has its own problems, chief among which is whether risk (two of their four factors) is properly conceptualized as a dimension of involvement or as a separate construct (compare Chaffee and McLeod 1973; Bloch and Richins 1983; Rossiter and Percy 1987). If these concerns were to be placed aside, however, the two remaining dimensions (importance and pleasure) dovetail nicely with the two factor theory of involvement developed by Park and Mittal (1985). These authors argue that there exists both cognitively based and affectively based involvement. Heightened involvement can result either from functional consequences ("It is important that I attend to this product") or emotional consequences ("It gives me enjoyment to attend to this product"). This two factor conceptualization of Park and Mittal is consistent both with subsequent work by Zaichkowsky (1987), and with an earlier tradition in the advertising discipline (Ratchford 1987; Vaughn 1980).

In this paper, we use the terms "importance" and "interest" to refer to these two aspects of the involvement response. Our position is that while the descriptors "important" and "interesting" are equally reflective of the felt involvement construct, they are not synonymous. Importance and interest represent correlated but distinct facets of felt involvement. Many products will strike a consumer as interesting and important to an equal degree; others will appear to be one but not the other. Hence, an involvement inventory needs to sample items from both domains, so that it can yield both an overall score and two subscores. This is particularly necessary if it should prove the case that the two dimensions differentially drive outcome behaviors such as information search, or vary in their effects across product categories. While Zaichkowsky (1985) did not make this distinction, the original PII appears to contain items from both the importance domain (e.g., "matters to me") and the interest domain (e.g., "exciting"). Our proposed revision will augment the interest domain (which appears to be represented by fewer items in the original PII).

METHOD

Sample and Procedure

Self administered questionnaires were completed by 146 students and 103 non-students; the total sample is 51% male and 49% female. The non-student sample consists of working adults over the age of 30; non-students were included to maintain comparability with Zaichkowsky's (1985) samples. Each respondent rated three products that were presented free of context (i.e., non-situated), and then a fourth product that was presented in two different situations. Ratings were made on a 22 item semantic differential that included the original PII plus two new item-pairs described below. Respondents also rated the three non-situated products on measures of attitude and information search and processing, as described below. Three different rating forms, each containing four products, were used in the research. The forms differed only in the specific products listed. The total of twelve products rated in the study include all the products used by Zaichkowsky with the exception of bubble bath (excluded in view of its gender-specific consumption). Within each rating form, one-half the respondents rated the products in one order, while the other half rated them in counterbalanced order. Across the three rating forms, PII scores for each group of non-situated products had been found to be roughly equal by Zaichkowsky (1985). After elimination of incomplete questionnaires, there were 1171 usable cases.

Measures

Involvement. Two new-item pairs were added to the PII: "fun-not fun" and "dull-neat". These were chosen by the authors to tap the interest facet of involvement, and to help alleviate the polysyllabic character of the PII. For analytic purposes the 22 item pairs representing involvement can be characterized in several ways as shown in the Exhibit. The RPII consists of eight item-pairs drawn from the original PII plus the two new item-pairs. The RPII is divided as shown into two sub-scales referred to as Importance and Interest. The Discard measure consists of those items in the PII that we propose to eliminate. Since the RPII is largely a subset of the PII, most analyses compare the RPII to the Discard measure rather than the PII. The general hypothesis is that the items in the Discard set either serve no useful purpose or actually have a debilitating effect.

EXHIBIT

ASSIGNMENT OF ITEMS USED TO RATE INVOLVEMENT TO THE PII, RPII, AND DISCARD MEASURES

Attitude. Five item pairs (good-bad, ugly-beautiful, pleasant-unpleasant, awful-nice, positive-negative) were selected from the literature on the semantic differential (Osgood, Suci and Tannenbaum 1957; Osgood 1969). Each pair had very high ratings on the Evaluation factor in that literature. Coefficient alpha for the sum is .92.

Information Search and Processing. The five items used by Zaichkowsky (1985) and five additional items drawn from the literature were used to measure commonly accepted outcomes of a state of involvement (Table 1). In addition to examining individual items, the analyses also use the sum of those eight of the ten items that were not related to brand commitment (see note to Table 1; coefficient alpha for this sum is .94).

Situational Differences. Involvement with three of the products studied (red wine, calculators, and cameras) was examined across two situations. For red wine, this was the exact public vs. private situation distinction used by Zaichkowsky; for calculators it was self vs. gift purchase situation, while for cameras it was everyday use vs. use on an overseas vacation.

TABLE 1

COMPARISON OF THE PII, RPII AND THE DISCARD IN THE PREDICTION OF INVOLVEMENT OUTCOMES

RESULTS

Internal Consistency

Coefficient alphas for the PII and the RPII were computed over the nine products rated in the study, over the six situated products, and for each product and situated product individually. The reliability of both the RPII and the Importance and Interest sub-scales, when measured across multiple product categories, is very good in an absolute sense at .95, and almost as good as the PII, whose reliability is .98. In terms of individual products, the superiority to be expected from the lengthier PII is more apparent. In several cases reliability for the RPII and its sub-scales dips to the low or mid .80's, while that for the PII never dips below .92. Nevertheless, in about three-fourths of the individual product ratings the reliability of the RPII and its two sub-scales equals or exceeds .90. To measure test-retest reliability, three of the products (facial tissue, headache remedy and mouthwash) were rated a second time by 60 students after a three week interval. Over the three products, test-retest correlations for the PII ranged from .59 to .85, and for the RPII from .53 to .78. As with coefficient alpha, the PII has a slight reliability advantage over the RPII.

Usability

The PII contains 143 syllables in 57 words ( = 2.51), the RPII contains 66 syllables in 36 words ( = 1.83), and the Discard contains 73 syllables in 24 words ( = 3.04). The syllable-word ratio in the RPII, when compared item by item is significantly less than for the PII (t = 2.62, p = .01). A lower syllable count is often associated with greater readability and ease of comprehension (Locker 1989). As an additional test of usability, 65 undergraduates, predominately of Junior standing, rated each unique word in the PII. They were asked which of these words they used in speech or writing. Four words in the PII were found to be problematic: superfluous (77% did not use), mundane (62%), vital (23%) and fundamental (22%). These analyses strongly suggest the need to simplify the PII if it is to be applicable to broader populations outside of an elite university setting.

TABLE 2

EFFECTIVENESS OF THE PII AND RPII IN DISCRIMINATING INVOLVEMENT ACROSS SITUTATIONS

Factor Structure

Principal components factor analyses with varimax rotation were performed on the PII and the RPII for the nine products taken in the aggregate, the six situated products in the aggregate, and over the 9 individual products and 6 situated products (Table 2). In both the aggregate analyses the PII revealed one major and one minor factor, exactly as reported by Zaichkowsky (1985). On an individual product basis the results for the PII are less clear. In 8 of 15 cases, the PII exhibited more than two factors, with as many as five in the case of automobiles and calculators purchased for a friend. This casts serious doubt on whether the 20 item PII really measures a single dimension of involvement as claimed by Zaichkowsky (1985).

The RPII had a two factor structure in both of the aggregate analyses. In the analyses of the 15 individual product ratings (nine non-situated, six situated), the RPII showed only a single factor in four cases, and two factors in the remaining eleven cases. The occasional absence of a second factor is probably a result of the high correlation between Importance and Interest (r = .66 overall).

Discriminant Validity

Surprisingly, both the RPII and the Discard measure have approximately equal correlations with the attitude measure (r = .76). This undermines our contention that the PII is more confounded with attitude than is the RPII. However, the results are somewhat more encouraging when the Importance and Interest sub-scales of the RPII are examined separately. The sub-scale correlations with the attitude measure are .74 and .65, respectively. The latter correlation is significantly lower than the Discard-Attitude correlation of .76 when Steiger's (1980) test for dependent correlations is applied ( = 5.41, p < .001). It appears that the PII is not alone in having a high correlation with attitude. However, these findings also suggest that measures of interest are more distinct from measures of attitude than are measures of personal relevance (the Importance sub-scale). The sub-scale structure of the RPII thus offers some assistance to the researcher who seeks the greatest possible differentiation between measures of involvement with the object versus attitude toward the object.

Criterion Validity

This section compares the performance of the PII, the Discard and the RPII measures in the prediction of ten outcomes of involvement. To maintain comparability we first examine results for the five behaviors originally studied by Zaichkowsky (1985), despite the fact that two of these items probably measure brand involvement rather than product involvement. As shown in Table 1, the RPII is nominally superior to the PII in four out of five cases. The one exception concerns having a preferred brand. Even here, the five item Importance sub-scale predicts this behavior as effectively as the twenty item PII.

The next analysis examines the sum of eight items (three from Zaichkowsky, five added by us) which measure information search and processing (see note to Table 1). This sum provides a more reliable indicator of involvement outcomes than any individual behavior. Looking at the aggregate of nine products, the RPII is again superior to the PII, accounting for 45.2% of the variance in information search and processing, as compared to 40.3% for the PII. The difference between the two correlations is significant by Steiger's (1980) test ( = 4.44, p < .001). A more conclusive test is to examine the incremental contribution (I2) in predicting information search and processing obtained by adding the Discard measure to an equation that contains the RPII measure (Cohen and Cohen 1983). This analysis shows no significant contribution by the Discard measure in a hierarchical regression analysis (I2 = .001, NS).

Because the PII was found to be especially reliable on an individual product basis, this hierarchial regression analysis was repeated on a product by product basis. For eight of nine products, the addition of the Discard measure again failed to improve upon the prediction of outcomes obtained from the RPII (the exception is color televisions). These individual product analyses indicate that in most cases the items in the Discard measure perform no useful function from the standpoint of prediction of information search and processing.

Also of note are analyses of the attitude measure in prediction of information search and processing. Despite the high correlation between attitude and both Zaichkowsky's PII and our RPII measures of involvement, attitude is clearly inferior as a predictor of behavioral outcomes, accounting for but 27% of the variance in the eight item sum.

Discrimination Among Situations

Red wine, calculators and cameras were each presented to respondents in two distinct situational contexts. The PII successfully discriminated between two situations in the case of three different products examined in three different types of situations (Table 2), as would be expected of a measure of felt involvement (Celsi and Olson 1988; Peter and Olson 1987). We also found the RPII to be about as effective as the PII in this task. The RPII is also able to discriminate differing degrees of involvement across situations in all three cases; however, in a discriminant analysis it does not correctly classify quite as many cases as the PII (Table 2). On the other hand, in a hierarchical discriminant analysis where the RPII is entered first, the Discard measure does not add significantly to the RPII's discrimination between situations in two of three cases (red wine and cameras). The roughly equivalent performance of the RPII, in conjunction with the limited incremental value of the Discard measure, suggest that the extra items in the PII may be of limited value when the goal is to discriminate degree of felt involvement with a product across multiple situations.

Construct Validity

Implicit in the Park and Mittal (1985) theory is the idea that the involvement response by an individual to a product may be a function of either the perceived importance it has, or its interest value, or both. This suggests an examination of the relative contribution of the Importance and Interest sub-scales of the RPII in predicting information search and processing. Using the eight item sum of information search and processing, and now looking at each product individually, Table 3 shows that for facial tissues, headache remedies, and laundry detergent, Importance is clearly a better predictor of involvement outcomes than Interest. In fact, for the first two products, Interest makes no incremental contribution to the prediction of outcomes. For automobiles, color televisions, instant coffee, and jeans, the reverse is true: Importance is less predictive than Interest, and affords no increment in prediction. For breakfast cereal and mouthwash, outcomes appear to be driven by both Importance and Interest. Taken together, the above analyses indicate the utility of distinguishing between the importance and interest facets of involvement.

DISCUSSION

One finding of this study is the strong performance of Zaichkowsky's PII across a number of validation tests. It is exceedingly reliable; it is highly predictive of a broad range of behavioral outcomes associated with involvement; and it is able to successfully discriminate felt involvement across several products and a variety of situations. The last two validation tests go beyond the evidence provided by Zaichkowsky (1985) in her original article. However, the PII also appears to suffer several limitations. It is unnecessarily long and elaborate; needlessly difficult to comprehend; insufficiently predictive of information search and processing outcomes; and unduly narrow in its conceptualization. The revised version of the PII examined in this paper appears to retain what is best in the original PII while offering a number of significant improvements and incurring no major liabilities. The ten item RPII is one-half as long as the PII while remaining very reliable; uses mostly short and simple words; is strongly predictive of information search and processing; and is effective at discriminating felt involvement across situations.

The most significant weakness of the RPII in comparison with the PII is its somewhat lower although still quite high reliability, as evidenced by both coefficient alpha and test-retest correlations. This weakness is most apparent at the individual product level. There are probably some situations, involving the correct classification of respondents into groups or with respect to some cut-off value, where this lowered reliability may argue for use of the PII instead of the RPII. However, even here the investigator will have to weigh the PII's reliability advantage against its more polysyllabic character and the associated difficulties in comprehension. Similar comments apply when the investigator seeks to discriminate among situations.

TABLE 3

COMPARISON OF IMPORTANCE AND INTEREST SUB-SCALES OF THE RPII IN THE PREDICTION OF MULTIPLE OUTCOMES ACROSS PRODUCTS

There is clearly a need for additional theoretical work on how favorability and involvement are related in the case of specific products. For the products we examined, both the RPII and the PII were highly correlated with the attitude (although the interest sub-scale is less so). The fact that the involvement measures are much better than the favorablity measure at predicting information search and processing is certainly grounds for retaining the distinction between involvement and attitude. In future research it might be interesting to attempt to identify, on the one hand, products which are favorably regarded but uninvolving, and on the other, products which are unfavorably regarded but involving. Close examination of such products might help to disentangle the relationship between involvement and attitude.

The other conceptual finding of note is that involvement cannot be reduced to either personal relevance (i.e., importance) or interest. Most contemporary definitions (e.g., Bloch and Richins 1983; Cohen 1983; Mitchell 1979; Rothschild 1984; Zaichkowsky 1985) emphasize either the one or the other of these facets. Conceptualizations that identify the involvement construct with interest need to deal with product categories such as headache remedies where interest is quite unable to predict a wide range of behaviors typically associated with involvement. Similarly, conceptualizations that identify involvement with personal relevance need to grapple with product categories such as jeans, where importance is a weak predictor of outcomes. In the meantime, the results reported here, in conjunction with theoretical work by Park and Mittal (1985) and also Laurent and Kapferer (1985), Ratchford (1987), Vaughn (1980), and Zaichkowsky's (1987) own later work argue for a multidimensional conceptualization of involvement. Whether importance and interest should be modelled as antecedents, or as facets, or as alternative expressions of involvement, is a task for future research. Here again it would be useful to examine some extreme cases: products that are important but uninteresting, or interesting but unimportant.

In conclusion, the findings indicate that the RPII represents a viable alternative to the PII for measuring involvement. Researchers who need a short measure with high criterion validity, and who can tolerate a slight decrease in reliability, may choose to use it in preference to the PII.

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