The cognitive components of subjective well-being can be measured with the Satisfaction with life scale (SWLS) and the Harmony in life scale (HILS), which both comprise five items each. The aim of this article is to abbreviate these scales and examine their psychometric properties and validity. Three datasets including test-retest data are used (N = 787; N = 860; N = 343). The two first datasets were already collected, whereas the third dataset included delivering the three-item scales (SWLS-3; HILS-3) together (in random order) with one shared instruction. The last study was pre-registered, including open data and code. The SWLS-3 and the HILS-3 demonstrate good psychometric properties, including very high internal consistency and item total correlations, strong test-retest reliability, where two-factor models of cognitive well-being tend to yield very good fit indices. Further, the scales demonstrate measurement invariance across time and gender. In fact, the three-item scales demonstrate as strong psychometric properties as compared with the five-item scales. Additionally, the scales demonstrate similar validity by yielding similar correlations to assessments of well-being, mental health problems and social desirability. Thus, the SWLS-3 and the HILS-3 can efficiently be used together with one shared instruction, without compromising (and in most aspects even yielding small improvements) the psychometric soundness of the scales.
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