Evaluating Sexual Objectification Instruments and the Cumulative Evidence of their Psychometric Properties: A Systematic Review

Background: Sexual objectification, a psychological process whereby individuals are rendered as sexual objects, has become increasingly evident in mass media. Accurate measurement is imperative given its associated negative outcomes for adults and children; however, there has yet been a systematic evaluation of sexual objectification instruments.

Method: Articles that included self-report instruments measuring sexual objectification were identified through MEDLINE Complete, ProQuest Central, Psychology and Behavioural Sciences Collection, PsycINFO, and Web of Science. Reference lists were also examined for potentially relevant articles. The following characteristics were recorded for each instrument where available: (a) sampling methods and characteristics, (b) number of items, item development, scales and subscales, response anchors and score ranges, (c) description of instrument, (d) targets of sexual objectification, (e) reliability and (f) validity.

Results: Forty-four studies and 21 instruments were identified. There were variabilities in how instrument items were generated and how instruments measured and defined sexual objectification. There were also limited psychometric evaluations for almost all instruments, including concurrent, predictive, convergent, and known-groups validities. Consequently, evidence of cumulative validity was gathered by examining studies that used these instruments.

Conclusion: While researchers are given various options for instrument selection, very limited attention has centred on ensuring that existing sexual objectification instruments are psychometrically sound. Future research may benefit from refining these instruments to ensure that they have stable psychometric properties.

Evaluating Sexual Objectification Instruments and the Cumulative Evidence of their Psychometric Properties: A Systematic Review

Western societies have seen a notable rise of sexualisation in mass media as content analyses demonstrate that men, women, and young girls have been increasingly sexualised over recent decades (Collins, 2011; Graff, Murnen, & Krause, 2013; Hatton & Trautner, 2011; Rohlinger, 2002). Specifically, their bodies are often portrayed in overly provocative ways in television, magazines, and advertising, arguably with the intent of selling a product or attracting the viewer’s attention (Vaes, Paladino, & Puvia, 2011). Such sexualised portrayals often lead to unrealistic cultural standards of beauty and promote what researchers have labelled as the sexual objectification of these individuals (Fredrickson & Roberts, 1997). Sexual objectification is the psychological process of perceiving an individual as a sexual object devoid of any individuality, scrutinising their appearance for pleasure or evaluation, and/or imposing sexuality upon them (LaCroix & Pratto, 2015; McKinley & Hyde, 1996). Objectified individuals are regarded as mere instruments to be consumed by others, which in turn can result in severe consequences (Loughnan et al., 2010).

Consequences of Sexual Objectification

Ample evidence to date has demonstrated that constant sexual objectification is associated with negative mental health outcomes. Among these outcomes is the notion of self-objectification[1], where objectified individuals internalise observers’ perspectives and subsequently appraise their physical appearance to assimilate to cultural standards of beauty (Fredrickson, Roberts, Noll, Quinn, & Twenge, 1998). According to objectification theory (Fredrickson & Roberts, 1997), which is a theoretical feminist framework for explaining the ramifications of sexual objectification for women, self-objectification subsequently leads to experiencing shame and anxiety over one’s own appearance and disordered eating behaviours. Current research has confirmed this assertion, with studies demonstrating the direct and indirect positive relationships between sexual objectification and media consumption, body shame, appearance anxiety, and disordered eating behaviours (see Moradi & Huang, 2008 for a detailed review).

Evidence also suggests that sexual objectification further perpetuates gender oppression and discrimination (Fredrickson & Roberts, 1997; Gardner, 1995). For example, individuals who objectify others are more likely to endorse sexist beliefs or stereotypical gender roles, pressure others to have sex (i.e., sexual coercion), or engage in sexual harassment (Rudman & Mescher, 2012; Davidson, Gervais, & Sherd, 2015). Current research also indicates that objectified individuals are more likely to report experiencing sexual harassment or sexual coercion (Fairchild & Rudman, 2008; Harned, 2000; Miles-McLean et al., 2015). Taken together, the academic literature has confirmed that sexual objectification is related to severe ramifications that occur on both an individual and interpersonal level. While the academic literature has mainly focused on women, a growing body of evidence has indicated that sexual objectification can occur for and have the same deleterious impact on men and young girls (Graff, Murnen, & Smolak, 2012; Holland & Haslam, 2016; Loughnan et al., 2010; Davidson, Gervais, Canivez, & Cole, 2013). Such evidence aligns with the idea that anyone can be objectified (Nussbaum, 1995).

Given the heightened promotion of sexual objectification in mass media over recent decades and its associated consequences, scientific interest and research have emerged to understand this social phenomenon in order to develop and evaluate related interventions (Loughnan et al., 2010). In response several instruments have been developed to measure sexual objectification in the academic literature.

Quantifying Sexual Objectification

Various methodologies have been introduced to determine how best sexual objectification should be measured. An overwhelming majority of studies have developed or used instruments that rely on self-reports, either through Likert-type questionnaires (e.g., Interpersonal Sexual Objectification Scale [ISOS]; Kozee, Tylka, Augustus‐Horvath, & Denchik, 2007), ranking the importance of body parts (e.g., Other-Objectification Scale [OOQ]; Strelan & Hargreaves, 2005) and human attributes (e.g., Mental State Attribution Task [MSAT]; Loughnan et al., 2010), or reporting sexual objectification experiences on a “Yes/No” response format (e.g., Sexual Experiences Survey [SES]; Carr & Szymanski, 2011). Although the use of these instruments is valuable in measuring constructs in a simple and efficient manner, bias can occur as respondents are able to modify their answers because of personal motivations or social desirability concerns. Most recently, the use of implicit and indirect instruments have gained traction as ways of circumventing bias by examining non-conscious objectifying cognitions (Rudman & Mescher, 2012); however, evaluating these instruments are beyond the scope of this review, particularly as their use in the academic literature remains scarce (Vaes et al., 2011).

Self-report instruments have been widely used in examining sexual objectification over the past decade. Given its popularity, there exists a disproportionate and perhaps superfluous amount of instruments that have been developed during this somewhat brief period. It is possible that the large volume of instruments may be due to each instrument measuring different components or aspects of sexual objectification, particularly as there is yet no holistic view of the social phenomenon (Holland & Haslam, 2013). While the availability of multiple valid instruments is central to fostering good research and practice (Kerr & Holden, 1996), careful consideration is warranted in establishing effective instruments of sexual objectification and documenting and refining their psychometric properties. This point is made further salient when taking into account that good research is established on a solid foundation of measurement methods (Calogero, 2010).

Aim of Present Systematic Review

Sexual objectification – whether societal or internalised – is of great mental health and social importance. Therefore, the accurate measurement of sexual objectification is vital in studying and addressing its negative consequences for adults and children. Despite the various instruments used in sexual objectification research, there has not yet been a systematic evaluation of these measurement tools. The need for such an evaluation is evident since the real-world implications of the findings for those at risk of being objectified further augment the demand for using the most valid and reliable instruments. Accordingly, this systematic review aimed to evaluate self-report instruments that have been developed and used to measure sexual objectification and to record their psychometric properties (i.e., validities and reliabilities) as presented in the academic literature. By presenting an evaluation of the available instruments in the academic literature, it is hoped that researchers can make an informed selection of instrument(s) that correspond with their research questions and target populations rather than purely based on convenience.

Method

The following review on sexual objectification instruments was based on Cochrane procedures (Higgins & Green, 2008) and is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Moher, Liberati, Tetzlaff, & Altman, 2009) guidelines. As this review only focused on the availability and psychometric properties of sexual objectification instruments, the four Populations, Intervention, Comparison, and Outcome (PICO) elements were not incorporated in this review. Correspondingly, risk of bias analyses and quality assurances were not conducted as it was deemed irrelevant to a review of this nature. There has been no published protocol for this review.

A systematic search was conducted across five databases: MEDLINE Complete, ProQuest Central, Psychology and Behavioural Sciences Collection, PsycINFO, and Web of Science. Database searches involved combining terms associated with sexual objectification and measurement using the Boolean terms or and and (see Table 1). For example, articles containing a test or instrument of sexual objectification were included in the results. Terms were also abbreviated to search for multiple suffixes; that is, searching on objectif* would include results for objectification, objectifying, objectifies and objectified. The complete strategy for the PsycINFO search is shown in Appendix A.

Searches of titles and abstracts resulted in a total of 7,324 potentially relevant articles. Articles from the first available date to 8December 2016 were included, and were retained for analysis and review if they: (a) were written in English, (b) contained more than one item, (c) measured sexual objectification and, (d) did not use sexual objectification instruments solely for manipulation checks. Articles were also excluded if they were not original or peer-reviewed articles, and if they measured self-objectification. While sexual objectification and self-objectification are related constructs, they arguably involve different cognitive processes and possess unique antecedents and consequences (Fredrickson et al., 1997; Fredrickson et al., 1998).

After abstract and title screening the 7,324 articles to identify those that reported measuring sexual objectification, 560 full-text articles were then examined based on the inclusion and exclusion criteria. An additional three articles were also identified for possible inclusion from examining the reference lists of retained articles. Forty-four studies and 21 instruments were identified for qualitative analysis. Figure 1 displays the PRISMA statement addressing detailed reasons for exclusion.

Original articles reporting the development and validation of instruments were included whenever possible. In some studies sexual objectification was measured using either modified self-objectification instruments or existing instruments that were not originally developed to measure sexual objectification. In these instances, studies that first introduced the instrument to measure sexual objectification were included in the analysis in place of the original articles. The following characteristics were extracted for each instrument where available: (a) sampling methods and characteristics, (b) number of items, item development, scales and subscales, response anchors and score ranges, (c) description of instrument, (d) targets of sexual objectification, (e) reliability (i.e., test-retest, internal consistency, split-half reliability), and (f) validity (i.e., concurrent, predictive, convergent, and known-groups validity).

Results

Database searches yielded 7,324 articles, and 21 instruments were identified from the protocol presented in this review. A detailed description of these instruments and their psychometric properties are provided in Tables 2 through 4.

Background and Development

Information relating to the description, background, and development of each instrument is presented in Table 2, which indicated that instruments differed in how they were developed. Specifically, item development was informed by various sources, including the academic literature, experts, students, and other instruments. Two instruments were modifications of self-objectification instruments, and four instruments that were originally developed to assess different constructs (e.g., mind perception, moral status, sexual experiences, and sexism) were used to measure sexual objectification. The most commonly used statistical method for item selection was factor analysis.

Samples of high-school and college students were used in the development of 16 instruments. Correspondingly, most instruments (n=13) were developed using samples of primarily White or Caucasian respondents from Western countries, including Australia.

There is considerable variability in the criteria used to define and measure sexual objectification. Six ways of how sexual objectification is measured were identified in this review: (a) the frequency an individual reports encountering sexual objectification experiences; (b) the extent that women are considered sexual objects; (c) the frequency an individual reports objectifying others; (d) the degree of acceptance that men can objectify women; (e) ranking the importance of body- and appearance-related traits; and (f) the extent a target is attributed with personality- and human-related traits, including thoughts and emotions.

Seven instruments were used only once to measure sexual objectification in the academic literature. Most instruments (n=14) were originally developed to exclusively measure the sexual objectification of women. In comparison, only a few instruments were developed to measure the sexual objectification of both men and women (n=3) or girls (n=3). Only one instrument was developed to exclusively measure the sexual objectification of men, and no instruments were found to measure the sexual objectification of boys.

Instrument Characteristics

Instrument characteristics, including items, subscales, scaling, and scoring, are shown in Table 2. The mean number of items was 14.05, with a range from 4 to 40. Most instruments used a Likert-type response format to measure the degree of frequency or agreement/disagreement with items, with scales ranging from 5- to 9-points. The other two instruments adopted either a “Yes/No” response format, or a ranking system to organise respondents’ perceived importance of traits. Scores on a majority of instruments (n=19) are determined using the sums or averages of the items. For most instruments (n=14), higher scores indicate greater frequencies of being objectified or greater tendencies to objectify others. Directionality differed for all remaining instruments (n=7), with higher scores implying lesser tendencies to objectify others since respondents attribute greater personality- or human-related traits to a target.

Reliability

Information pertaining to instrument reliability is presented in Table 3. Internal consistency estimates (i.e., coefficient α) were available for most instruments (n=17), and ranged from.60 to .96. Three instruments did not report internal consistency estimates, while a coefficient α was not possible to calculate for one instrument because its scoring protocol required ranking items. Test-retest reliability estimates were available for only three instruments, which ranged from .72 to .93, and split-half and inter-rater reliability estimates were not available for any instrument.

Validity

Most articles examined the theoretical relationships between sexual objectification scores and relevant constructs (e.g., self-objectification), and differences on sexual objectification scores between selected groups of participants and/or targets (e.g., men vs. women). Information pertaining to evidence of instrument validity in prior studies – via significance testing (e.g., r values, t-tests, F-tests, R² values, B and β values) – is presented in Table 4. As the area of sexual objectification is currently somewhat limited in scope, psychometric evaluations were not provided for most instruments. Cumulative validity was therefore gathered in this review by evaluating the results from studies that used these instruments.

In accordance with Cronbach and Meehl’s (1955) conceptualisations of validity, concurrent validity is defined as the correlations between sexual objectification scores and variables theorised to be associated with sexual objectification. In the case of providing concurrent validity for sexual objectification instruments, variables used in the literature include: self-objectification, eating disorder symptoms, consumption and exposure to the media, sexist attitudes, and sexual coercion. Correlations between sexual objectification scores and other variables not traditionally associated with sexual objectification were also included in Table 4. Predictive validity is defined as the ability of sexual objectification instruments to predict performances on some future criterion, and convergent validity is defined as the correlations between scores on sexual objectification instruments (Cronbach & Meehl, 1955).  Sexual objectification scores were also examined across selected groups of participants to provide evidence of known-groups validity (Cronbach & Meehl, 1955). Ultimately, 15 of the 21 instruments established some form of validity.

Concurrent Validity: Variables Theorised to be Related to Sexual Objectification

Self-Objectification. Evidence for the hypothetical relationships between sexual objectification and self-objectification was established in seven instruments. Body shame and body surveillance (i.e., components of self-objectification), and self-objectification were associated with greater scores on instruments measuring the frequency of reported encounters with sexual objectification experiences or tendencies to objectify others. The strength of these correlations (i.e., r values) were generally small, but ranged from.15 to .69 (Mdn=.27). Only scores on three instruments demonstrated correlations equal to or greater than .30, which included the ISOS (Kozee et al., 2007), OOQ (Strelan & Hargreaves, 2005), and Partner-Objectification Scale (Zurbriggen, Ramsey, & Jaworski, 2011). All other instruments demonstrated correlations less than.30[2], suggesting that the strength between sexual objectification scores on these instruments and self-objectification were generally small.

Eating Disorder Symptoms. Four instruments established evidence for the theoretical relationships between sexual objectification and eating disorder symptoms. Men and women who reported engaging in disordered eating behaviours were more likely to score higher on instruments measuring how frequently they encountered sexual objectification experiences. The ISOS (Kozee et al., 2007) was the only instrument that consistently demonstrated correlations between sexual objectification scores and eating disorder symptoms that were above .30. Other instruments established correlations ranging from.15 to .28.

Consumption or Exposure to the Media. Evidence for the hypothetical relationships between sexual objectification and consumption or exposure to the media was established in seven instruments. Increased exposure to the media and consumption of pornography were associated with greater scores on instruments evaluating individuals’ tendencies to objectify others. Boys’ and girls’ exposure to sexually explicit media was also related to scores on instruments measuring their beliefs that women are sexual objects. Women who had a previous partner who frequently consumed pornography were also more likely to score higher on instruments evaluating how frequently they encountered sexual objectification experiences. Of all instruments, only the Women as Sex Objects Scale (Peter & Valkenburg, 2007) and Interpersonal Sexual Objectification Scale – Perpetrator (ISOS-P; Gervais, DiLillo, & McChargue, 2014) established correlations between sexual objectification scores and media consumption or exposure that were equal to or above .30. Other instruments demonstrated correlations ranging from.14 to .27.

Sexist Attitudes. Five instruments established evidence for the theoretical relationships between sexual objectification and sexist attitudes. Men who displayed hostility towards women or endorsed women’s traditional and sexual roles were likely to score higher on instruments evaluating their tendencies to objectify women. Women who reported unfair sexist treatment at school or work were also more likely to score greater on instruments measuring how frequently they encounter sexual objectification experiences. The ISOS (Kozee et al., 2007) and Objectified Body Consciousness Scale – Modified (OCB-M; Ramsey & Hoyt, 2015) were the only instruments that consistently established correlations between sexual objectification scores and sexist attitudes that were over .30. All instruments demonstrated correlations ranging from.14 to .37.

Sexual Coercion. Evidence for the hypothetical relationships between sexual objectification and sexual coercion was established in three instruments. Men who engaged in sexual violence or manipulated women to have sex were more likely to score greater in instruments evaluating their tendencies to objectify others. Women who reported encountering sexual objectification experiences were also more likely to feel coerced to have sex and perceive themselves as being manipulated by their partners to have sex. All instruments established correlations between sexual objectification scores and sexual coercion that ranged from .16 to .51.

Other Variables. Three instruments established evidence for the theoretical relationships between sexual objectification scores and psychological wellbeing, where women who reported greater frequencies of encountering sexual objectification experiences were more likely to report psychological distress, depression, and anxiety. Two instruments demonstrated positive correlations between scores on sexual objectification instruments and drug and alcohol use in men and women. Evidence for the hypothetical relationships between sexual objectification and age was also established in four instruments, with age being negatively associated with instruments measuring the frequency of reported encounters with sexual objectification experiences for men and women. Three instruments established positive correlations between sexual objectification scores and the internalisation of cultural beauty standards in men and women. Two instruments demonstrated positive correlations between sexual objectification scores and appearance-related outcomes, including increased drives for thin bodies in women and muscular bodies in men.

Predictive Validity: Sexual Objectification Scores Predicting Other Variables

Limited evidence exists regarding the predictive validity of sexual objectification instruments, with only four instruments providing some form of predictive validity. It is important to note, however, that no authors directly purported that these findings were evidence of predictive validity. Sexual objectification scores on instruments evaluating men’s tendencies to objectify women predicted men’s breast-size ideals, and sexual objectification scores on instruments measuring boys’ tendencies to objectify girls predicted boys’ exposure to sexy self-presentation. Correspondingly, scores on instruments measuring individuals’ tendencies to objectify others predicted relationship satisfaction for men and women, and sexual satisfaction for men.

Convergent Validity: Correlations with Other Sexual Objectification Instruments

Little evidence of convergent validity was found in this systematic review. Only four instruments were used in studies that demonstrated convergent validity, which included the ISOS (Kozee et al., 2007), SES (Carr & Szymanski, 2011), MSAT (Loughnan et al., 2010), and Human Emotions Task (Borinca, 2016); however, there were no assertions made by any author that these findings were evidence of convergent validity. The correlations reported for these instruments ranged from .42 to .43.

Known-Groups Validity: Differences in Sexual Objectification Scores Amongst Groups

Known-groups validity was observed in six instruments, with differences in gender and sexual orientation most commonly examined. In terms of gender differences, women reported encountering more sexual objectification experiences than men. Contrastingly, men reported sexually objectifying women more than women while boys also regarded women as sexual objects more than girls.

Heterosexual men reported encountering less sexual objectification experiences than heterosexual women, lesbians, and gay men, whom reported comparable levels of sexual objectification experiences. Similarly, gay men reported objectifying men more than heterosexual men. No authors explicitly claimed that any of these findings were evidence of known-groups validity.

Discussion

The theoretical tenets of objectification theory have been empirically tested with a variety of instruments that have been created in response to the growing scientific interest in sexual objectification. These instruments have been developed with the good intent of quantifying the components of sexual objectification in order to allow the documenting of this social phenomenon, and the development of interventions against its associated harmful ramifications. It is perhaps this good intent that has led to the precipitous development of many instruments that are under-evidenced in terms of their psychometric utility.

Although the rapid expansion of sexual objectification research and instruments is promising, researchers are faced with the challenging task of selecting the most appropriate instrument for their research. Consequently, this systematic review was conducted with the primary aim of identifying the available instruments for use in this area, and presenting their cumulative evidence. This was done with the explicit intention of allowing researchers to make informed decisions when selecting instruments for their research. This review identified 21 instruments that have been previously used to measure sexual objectification in the academic literature from 2001 until 2016. The outcomes of this review were based on the published psychometric properties and the related and available evidence of the use of each instrument. Three major observations emerged in this review, as discussed below.

Limited Psychometric Evaluations and Variations Among Instruments

There is a considerable lack of psychometric evaluation for sexual objectification instruments examined in this review. With the exception of the ISOS (Kozee et al., 2007), the psychometric properties of all instruments were seldom assessed by researchers. While internal consistency reliability estimates were provided for most instruments, cumulative validity was gathered in this review since there were limited psychometric evaluations in the original studies. Given the importance of using valid and reliable instruments in psychological research (Kaplan & Saccuzzo, 2017), the scarcity of assessing instruments’ psychometric properties is concerning because it calls into question whether these instruments are accurately measuring sexual objectification. Concerns are further raised in view of the different criteria used to assess sexual objectification and how these instruments were developed (i.e., issues involving content validity).

There are many variations regarding how instruments measure sexual objectification. Specifically, six ways of assessing the social phenomenon were identified in this review, which may be accounted for by the diverse explanations regarding what constitutes as sexual objectification. Instruments examined were also found to measure certain aspects or components of sexual objectification, thereby demonstrating that there is yet no instrument that comprehensively assesses the full range of the construct. For example, the ISOS (Kozee et al., 2007) specifically measures how frequently an individual encounters sexual objectification experiences while the Women as Sex Objects Scale (Peter & Valkenburg, 2007) specifically measures the extent an individual perceives women as sexual objects. Taken together, there is inconsistency with how sexual objectification is defined and measured, which may complicate researchers’ task of choosing the most suitable instrument for their research.

Disparities were also noted in how instrument items were generated, as previous research, existing instruments, and/or factor analyses were used to select items for inclusion; however, of all instruments, only three – the ISOS (Kozee et al., 2007), the Sexual Objectification Experiences Scale (SOES; Wiseman & Moradi, 2010), and Cultural Sexual Objectification Scale (CSOS; Hill & Fischer, 2008) – employed a panel of experts to generate and review items. When considering the importance of involving experts in establishing content validity (Hinkin, Tracey, & Enz, 1997), the dearth of expert opinion when developing instruments may cast doubt on whether the “best” items were retained or even generated to begin with. Respectively, the use of existing instruments is potentially problematic since these instruments may assess constructs that are related yet are different to sexual objectification (e.g., sexism). There is therefore a possibility that items included in these instruments may not sufficiently capture and assess the full range of the sexual objectification construct, which may render the content validity of these instruments negligible. Consequently, this reinforces the need for psychometric evaluations of current instruments to ensure that they validly and reliably measure sexual objectification.

Uniformity of Findings and Methodological Caveats

Despite the great variation in the measurement and development of these instruments, the findings were markedly uniform across studies. All instruments were related to variables associated with sexual objectification where examined, and there were no discrepancies in terms of the direction of the relationships. For example, greater tendencies to sexually objectify others and the frequency of reported encounters of sexual objectification experiences were consistently associated with higher levels of self-objectification, eating disorder symptoms, and media consumption and exposure. Taken together, the cohesive findings demonstrate some evidence of concurrent validity; however, the correlations were generally small, indicating weak relationships between scores on sexual objectification instruments and other examined variables. Such low correlations may likely be explained by the shortage of psychometric evaluations of instruments, the differing ways in which instruments have been developed, and how instruments define and measure sexual objectification. Nevertheless, the weak relationships indicate that existing instruments may largely demonstrate inadequate evidence of concurrent validity.

To a much lesser extent evidence of known-groups, predictive, and convergent validity were provided, with less than one third of instruments demonstrating any one of these validities. Regardless, the findings were strongly consistent across instruments despite not being explicitly stated by researchers as evidence of validity. For example, the findings unvaryingly demonstrated significant and meaningful positive relationships between four instruments, thereby indicating convergent validity. Although the consistency of these findings is encouraging, very little is known of the predictive utility of most sexual objectification instruments, their relationships with other similar instruments, and their ability to establish differences between sexually objectification scores across distinct groups. Accordingly, the limited validities of a majority of existing instruments may further hinder researchers’ efforts with selecting the most appropriate instrument for their research.

Despite the uniformity of the findings in the academic literature, there are some methodological caveats that should be considered. Evidently, the generalisability of the findings (i.e., external validity) is largely restricted to Caucasian, high-school and university-aged students or adult women. It is possible that individuals who are older, or who originate from a more socially conservative society, may respond differently to being sexually objectified or sexually objectifying others (Graff et al., 2012; Loughnan et al., 2015). Men and/or children may also experience sexual objectification in a dissimilar way to women (Graff et al., 2012). The limited external validity of findings is made more salient when taking into account that there are no normative data across all instruments. It is therefore not possible to establish what normative high or low scores would appear for any population, let alone to adequately make cross-cultural comparisons. Taken together, such caveats may impede our understanding of sexual objectification to a wider range of individuals in the community. Future research may therefore benefit from using more diverse samples – including cross-cultural, clinical, and minority populations – and incorporating normative data for these instruments.

Selecting the “Best” Instrument

The final albeit most important observation made in this review involves evaluating the quality of evidence and determining the “best” instrument to measure sexual objectification accordingly. It is important to note that it is difficult and perhaps inapposite to make such judgements given the great variation with how instruments define and measure sexual objectification.

Based on examining psychometric properties alone, the ISOS (Kozee et al., 2007) stands out as the most widely-used and psychometrically sound sexual objectification instrument. As opposed to other instruments, the ISOS relied on experts and the academic literature to ensure good scale and item development, demonstrated good internal consistency reliability and test-retest reliability estimates, and possesses the most extensive evidence of cumulative validity (i.e., 35 findings). Importantly, the ISOS (Kozee et al., 2007) is only appropriate for measuring how frequently an individual reports encountering sexual objectification experiences. Researchers wishing to measure respondents’ propensity to objectify others may consider the OOQ (Strelan & Hargreaves, 2005), which has the second most extensive evidence of cumulative validity (i.e., 23 findings); however, as this instrument was modified from a self-objectification instrument, it may not accurately represent or measure the sexual objectification construct.

Although researchers may first consider the ISOS (Kozee et al., 2007) and OOQ (Strelan & Hargreaves, 2005), other factors should be taken into account, including which instruments are of suitable length and reading level or possess subscales of interest. By referring to Tables 2 through 4 as a guide, researchers with specific hypotheses and populations can choose instruments that match their requirements. For example, researchers intending on assessing the frequency of sexual objectification experiences encountered by gay or bisexual men may consider the SOES (Wiseman & Moradi, 2010) since it was specifically developed to be used with sexual minority men. Correspondingly, researchers wishing to establish change over time with stable instruments may consider employing the SES (Carr & Szymanski, 2011) or the ISOS (Kozee et al., 2007) for which respondents’ scores have been strongly correlated between two different time points.

Limitations of the Systematic Review

This review has several limitations that warrant mention. Firstly, a single coder conducted this review, which may increase the possibility of bias and error. Secondly, only self-report instruments (e.g., questionnaires and scales) were examined in this review, thereby limiting the evaluations of other types of instruments that have been used to measure sexual objectification (e.g., implicit instruments). Lastly, this review was limited to English-speaking articles and did not include unpublished articles, conference articles, and dissertations. Future research may thus benefit from examining a broader and conceivable range of suitable instruments and articles to investigate and incorporate the findings into the academic literature.

Concluding Remarks

Sexual objectification research has flourished over recent decades, leading to the proliferation of instruments in the academic literature. While researchers are given a plethora of options for selecting an instrument, this review has demonstrated that very limited attention has centred on ensuring that these instruments are psychometrically sound. Instruments examined in this review varied considerably in terms of how they define and measure sexual objectification, as well as the extent they provided evidence of validity and reliability for tests’ scores. Most concerning is that some instruments did not demonstrate any evidence of validity or were only used once, signifying that they are not viable instruments for psychological research. Taken together, this review emphasises the imperativeness of ensuring that existing instruments have stable psychometric properties via evaluations of their validity and reliability. It is also important that a review of this nature is continually updated to reflect the current academic literature, particularly as instruments will require frequent refinement to ensure that they consistently and optimally measure sexual objectification.

Overall, there is importance placed on developing and selecting valid and reliable instruments in psychological research. Newer fields of psychology – like sexual objectification – are therefore not exempt from employing stringent protocols in developing and validating instruments. This point is made further salient when considering the implications of using psychometrically robust instruments. In using sexual objectification instruments that have adequate or strong evidence of validity and reliability, it becomes possible to accurately enhance our understanding of sexual objectification in order to minimise the harmful ramifications for sexually objectified individuals.

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Table 1

Sexual Objectification and Measurement Terms Used in Boolean Search

Note. Asterisks cause the search to include all possible suffixes to a term.

Table 2. Background and Development

(Continued)

Table 2. Background and Development (Continued)

(Continued)

Table 2. Background and Development (Continued)

(Continued)

Table 2. Background and Development (Continued)

Table 3. Instrument Characteristics and Reliability Evidence