The development of unbiased tests is crucial in the arena of language testing in order to ensure validity. To date, studies of bias in language testing have mainly focused on factors such as gender, native language, or academic background, inter alia. However, bias may also result from psychological factors. Therefore, the present study investigates the role of English as a Foreign Language -EFL- test takers’ emotioncy, defined as the emotions evoked by senses that one holds for an entity, in their test performance. Specifically, this study aimed to examine emotioncy for the form as well as the meaning of 20 words to find out whether it can lead to differential functioning of the items on a vocabulary test. To this end, two emotioncy scales and a vocabulary test were designed. Then, based on the data collected from 235EFL students, the participants were bisected into the Low-Group and the High-Group, once based on their emotioncy scores for each word form and then based on their emotioncy scores for each word meaning. Subsequently, Rasch model-based Differential Item Functioning -DIF- analysis was performed across the two groups. The results showed that the vocabulary test items functioned differentially across the two groups in both form and meaning classifications, favoring the High-Group. Therefore, the study provides evidence for emotioncy as a psychological source of test bias and discusses implications for language testing stakeholders.

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