Researchers have long been interested in studying differences in implicit motive between different groups. Implicit motives are typically measured by scoring text that respondents have written in response to picture cues. Recently, research on the measurement of implicit motives has made progress through the application of a dynamic Thurstonian item-response theory model (DTM; Lang, 2014 Lang, J. W. B. (2014). A dynamic Thurstonian item response theory of motive expression in the picture story exercise: Solving the internal consistency paradox of the PSE. Psychological Review, 121, 481–500. doi:10.1037/a0037011 [Crossref], [PubMed], [Web of Science ®] [Google Scholar] ) that captures 2 basic motivational processes in motivational research: motive competition and dynamic reduction of motive strength after a motive has been acted out. In this article, the authors use the DTM to investigate differential item functioning (DIF) in implicit motive measures. The article first discusses DIF in the context of the DTM. The authors then conduct a DIF analysis of data from a study that used a picture set of the Operant Motive Test (OMT; Kuhl & Scheffer, 2002) with participants from Cameroon, Germany, and Costa Rica. Results showed no evidence of DIF in 9 pictures and some evidence for DIF in 3 pictures. The authors show a partial invariance model can be specified and use this partial invariance model to study latent mean differences between Cameroon, Germany, and Costa Rica. The discussion focuses on the use of IRT DIF methods in future research on implicit motives.

We propose a model of volunteering and test its validity across four cultural groups. We hypothesize that individuals’ explicit prosocial motivation relates positively to sustained volunteering, which is conceptualized as a latent factor comprising activity as a volunteer, service length, service frequency, and hours of volunteering. Moreover, we introduced implicit prosocial motivation and hypothesized that the relationship between explicit prosocial motivation and sustained volunteering would be amplified by implicit prosocial motivation. Data were collected from samples in China, Germany, Turkey, and the United States. Results confirmed our expectation that, across cultures, sustained volunteering was associated with explicit prosocial motivation and that the relationship between explicit prosocial motivation and sustained volunteering was strongest when implicit prosocial motivation was also high. By including implicit prosocial motivation, our study offers a novel approach to identifying sustained volunteer involvement, which can be of particular relevance for recruitment activities of voluntary organizations across various cultural contexts.