Investment Model Scale

Abstract

The Investment Model Scale (IMS) is a widely used psychological instrument designed to operationalize the four core components of the Investment Model of commitment processes, primarily developed by Caryl Rusbult. This scale measures an individual’s level of commitment to a relationship by assessing four distinct yet interrelated factors: satisfaction level, quality of alternatives, investment size, and commitment level itself. It is specifically employed in social and relationship psychology research to predict relationship maintenance, stability, and persistence in various dyadic associations, including romantic partnerships and friendships, and has been adapted for organizational commitment research.

Keywords

Investment Model, Relationship commitment, Satisfaction Level, Quality of Alternatives, Investment Size, Relationship Maintenance, Psychological Scale, Interdependence Theory

Authors

Caryl E. Rusbult, Julie M. Martz, Christopher R. Agnew

Purpose

The primary purpose of the Investment Model Scale is to provide researchers with reliable and valid measures for the key components theorized to drive commitment within close relationships. Rooted in interdependence theory, the scale allows for the quantitative prediction of relationship stability, dissolution, and persistence behaviors (e.g., accommodation, willingness to sacrifice).

The scale structure ensures that each of the four core variables—satisfaction, alternatives, investment, and commitment level—is measured thoroughly through both facet-specific items and broader global items, offering a robust assessment framework for testing the predictive power of the Investment Model across diverse populations and relationship contexts.

Construct

The scale measures four distinct, yet conceptually linked, psychological constructs central to the Investment Model (Rusbult, 1980, 1983):

• Satisfaction Level: Reflects the degree to which an individual feels positive about the relationship, based on the ratio of rewards received versus costs incurred, often compared against a personal Comparison Level (CL).
• Quality of Alternatives: Represents the perceived desirability of options outside the current relationship. This includes alternative partners, being single, or focusing on non-relational aspects of life (e.g., career, friends). Lower perceived quality of alternatives typically increases commitment level.
• Investment Size: Refers to the resources, both intrinsic (e.g., time, emotional disclosure, shared memories) and extrinsic (e.g., shared possessions, mutual friends, community identity), that a person has put into the relationship and that would be lost if the relationship ended. Greater investment size leads to higher commitment.
• Commitment Level: The central outcome variable, defined as the intention to persist in a relationship, including long-term orientation and psychological attachment to the partner.

Validity

The development of the Investment Model Scale (Rusbult et al., 1998) was supported by evidence of strong construct and predictive validity. The scale components consistently relate to theoretical outcomes as predicted by the model: satisfaction and investment size show positive correlation with commitment, while quality of alternatives shows a negative correlation.

The scale has demonstrated high predictive validity, successfully forecasting relationship maintenance behaviors (such as accommodation and willingness to sacrifice) and long-term outcomes, including relationship persistence and dissolution, across various longitudinal studies. Its application has extended beyond romantic relationships to organizational commitment, further supporting its utility and generalizability (Bayer, 2009).

Reliability

The Investment Model Scale exhibits high levels of internal consistency across all four subscales, as reported in the original validation study (Rusbult et al., 1998) and subsequent research. The reliability coefficients (Cronbach’s alpha) indicate that the items within each subscale reliably measure their intended construct:

• Commitment Level: Global items demonstrated strong internal consistency (alpha 0.91, 0.91, 0.95; overall $alpha = .90$).
• Satisfaction Level: Global items showed excellent reliability (0.92, 0.95, 0.94; overall $alpha = .87$).
• Investment Size: Global items also maintained high reliability (alpha .84, .84, .82; overall $alpha = .88$).
• Quality of Alternatives: Global items showed acceptable to good reliability (alpha 0.82, 0.85, 0.88; overall $alpha = .82$).

Factor Analysis

Although specific details of exploratory or confirmatory factor analysis beyond the implied four-factor structure are often detailed in the original publication (Rusbult et al., 1998), the scale is designed based on the theoretical premise of four distinct, orthogonal components: Satisfaction, Alternatives, Investment, and Commitment. Research consistently supports this underlying four-factor structure, confirming that the items cluster appropriately to measure these separate constructs, which then combine predictably to determine overall commitment level.

Instrument

Test Type: Psychological Scale (Self-Report Questionnaire)

Format: Multi-item scale using a Likert-type response format (9-point scale).

Language Available: English (Widely translated into various languages for cross-cultural research).

Population Group: Individuals in close relationships (e.g., dating, married, cohabiting couples, or organizational members in adapted versions).

Age Group: Adolescents and Adults.

Population Details: Originally validated on heterosexual romantic partners, but applicable across various relationship types and orientations.

Test Methodology: Respondents rate their agreement with statements regarding their current relationship using a 9-point scale ranging from 0 (Do Not Agree At All) to 8 (Agree Completely).

Keywords

Social Psychology, Relationship Science, Dyadic Relationships, Commitment Theory, Relationship Dissolution, Internal Consistency, Psychometrics, Interdependence

Authors

Author ORCID Identifier: Not specified in source.

Affiliation Email addresses: Not specified in source.

Correspondence Address: Not specified in source. Caryl E. Rusbult was affiliated with the Department of Psychology, University of North Carolina at Chapel Hill, at the time of publication.

Permissions & Fee and Test Year

The scale was published in 1998 by Rusbult, Martz, and Agnew. The scale is generally considered available for non-commercial academic research use, though researchers should verify copyright status with the original authors or publishers (Personal Relationships journal).

The original PDF of this instrument can be downloaded here: http://carylrusbult.com/documents/InvestmentModelScales.pdf

Reference’s

• Rusbult, C. E. (1980). Commitment and satisfaction in romantic associations: A test of the investment model. Journal of Experimental Social Psychology, 16, 172-186.
• Rusbult, C. E. (1983). A longitudinal test of the investment model: The development (and deterioration) of satisfaction and commitment in heterosexual involvements. Journal of Personality and Social Psychology, 45(1), 101-117.
• Rusbult, C. E., & Farrell, D. (1983). A longitudinal test of the investment model: The impact on job satisfaction, job commitment, and turnover of variations in rewards, costs, alternatives, and investments. Journal of Applied Psychology, 68, 429-438.
• Rusbult, C. E., Drigotas, S. M., & Verette, J. (1994). The investment model: An interdependence analysis of commitment processes and relationship maintenance phenomena. In D. J. Canary & L. Stafford (Eds.) Communication and relational maintenance (pp. 115-139). San Diego: Academic Press.
• Rusbult, C. E., Martz, J. M., & Agnew, C. R. (1998). The Investment Model Scale: Measuring commitment level, satisfaction level, quality of alternatives, and investment size. Personal Relationships, 5; 357-391.
• Bayer, Lucy. (2009). The Investment Model and Organizational Commitment: Predicting Workplace Behaviors. Haverford College. Dept. of Psychology. Thesis (B.A.). Available electronically from http://hdl.handle.net/10066/3733.
• Rusbult, Caryl E.; Agnew, Christopher; and Arriaga, Ximena, “The Investment Model of Commitment Processes” (2011). Department of Psychological Sciences Faculty Publications. Paper 26. http://docs.lib.purdue.edu/psychpubs/26.

Items of the Investment Model Scale

Satisfaction Level Facet and Global Items

1. Please indicate the degree to which you agree with each of the following statements regarding your current relationship (circle an answer for each item).

• (a) My partner fulfills my needs for intimacy (sharing personal thoughts, secrets, etc.)
• (b) My partner fulfills my needs for companionship (doing things together, enjoying each other’s company, etc.)
• (c) My partner fulfills my sexual needs (holding hands, kissing, etc.)
• (d) My partner fulfills my needs for security (feeling trusting, comfortable in a stable relationship, etc.)
• (e) My partner fulfills my needs for emotional involvement (feeling emotionally attached, feeling good when another feels good, etc.)

2. I feel satisfied with our relationship (please circle a number).

3. My relationship is much better than others’ relationships.

4. My relationship is close to ideal.

5. Our relationship makes me very happy.

6. Our relationship does a good job of fulfilling my needs for intimacy, companionship, etc.

Quality of Alternatives Facet and Global Items

1. Please indicate the degree to which you agree with each statement regarding the fulfillment of each need in alternative relationships (e.g., by another dating partner, friends, family).

• (a) My needs for intimacy (sharing Don’t personal thoughts, secrets, etc.) could be fulfilled in alternative relationships
• (b) My needs for companionship (doing things together, enjoying each other’s company, etc.) could be fulfilled in alternative relationships
• (c) My sexual needs (holding hands, kissing, etc.) could be fulfilled in alternative relationships
• (d) My needs for security (feeling trusting, comfortable in a stable relationship, etc.) could be fulfilled in alternative relationships
• (e) My needs for emotional involvement (feeling emotionally attached, feeling good when another feels good, etc.) could be fulfilled in alternative relationships

2. The people other than my partner with whom I might become involved are very appealing (please circle a number).

3. My alternatives to our relationship are close to ideal (dating another, spending time with friends or on my own, etc.).

4. If I weren’t dating my partner, I would do fine-I would find another appealing person to date.

5. My alternatives are attractive to me (dating another, spending time with friends or on my own, etc.).

6. My needs for intimacy, companionship, etc., could easily be fulfilled in an alternative relationship.

Investment Size Facet and Global Items

1. Please indicate the degree to which you agree with each of the following statements regarding your current relationship (circle an answer for each item).

• (a) I have invested a great deal of time in our relationship
• (b) I have told my partner many private things about myself (I disclose secrets At All Slightly Moderately Completely to him/her)
• (c) My partner and I have an intellectual life together that would be difficult to replace
• (d) My sense of personal identity (who I am) is linked to my partner and our relationship memories
• (e) My partner and I share many memories

2. I have put a great deal into our relationship that I would lose if the relationship were to end (please circle a number).

3. Many aspects of my life have become linked to my partner (recreational activities, etc.), and I would lose all of this if we were to break up.

4. I feel very involved in our relationship-like I have put a great deal into it.

5. My relationships with friends and family members would be complicated if my partner and I were to break up (e.g., partner is friends with people I care about).

6. Compared to other people I know, I have invested a great deal in my relationship with my partner.

Commitment Level Items

1. I want our relationship to last for a very long time (please circle a number).

2. I am committed to maintaining my relationship with my partner.

3. I would not feel very upset if our relationship were to end in the near future.

4. It is likely that I will date someone other than my partner within the next year.

5. I feel very attached to our relationship-very strongly linked to my partner.

6. I want our relationship to last forever.

7. I am oriented toward the long-term future of my relationship (for example, I imagine being with my partner several years from now).

Commitment Level-Global items (alpha 0.91, 0.91, 0.95)

• I am committed to maintaining my relationship with my partner.
• I want our relationship to last for a very long time.
• I feel very attached to our relationship-very strongly linked to my partner.
• It is likely that I will date someone other than my partner within the next year. (-)
• I would not feel very upset if our relationship were to end in the near future.a (-)
• I want our relationship to last forever.
• I am oriented toward the long-term future of my relationship Our relationship is likely to end in the near future. (-)

Satisfaction Level-Global items (0.92, 0.95, 0.94)

• I feel satisfied with our relationship.
• My relationship is much better than others’ relationships.
• My relationship is close to ideal.
• Our relationship makes me very happy.
• Our relationship does a good job of fulfilling my needs for intimacy

Quality of Alternatives-Global items (alpha 0.82, 0.85, 0.88)

• My alternatives are attractive to me (dating another, spending time. . .).
• My alternatives to our relationship are close to ideal
• If I weren’t dating my partner, I would do fine-I would find another appealing.
• The people other than my partner . . . are very appealing.
• My needs for intimacy, companionship, etc., could easily be fulfilled
• I weren’t involved in a dating relationship, I would enjoy spending time

Investment Size-Global items (alpha .84 .84 .82)

• I have put a great deal into our relationship that I would lose
• Compared to other people I know, I have invested a great deal
• I feel very involved in our relationship-like I have put a great deal into it.
• Many aspects of my life have become linked to my partner.
• My relationships with friends and family members would be complicated.
• I have invested a great deal in our relationship that I would lose
• I have put things into our relationship that would be lost if our relationship
• There are special activities that are associated with our relationship
• There are things that are now tied to our relationship that I would lose