For preference comparisons of paired successive musical excerpts, Koh (American Journal of Psychology, 80, 171-185, 1967) found time-order effects (TOEs) that correlated negatively with stimulus valence-the first (vs. the second) of two unpleasant (vs. two pleasant) excerpts tended to be preferred. We present three experiments designed to investigate whether valence-level-dependent order effects for aesthetic preference (a) can be accounted for using Hellström's (e.g., Journal of Experimental Psychology: Human Perception and Performance, 5, 460-477, 1979) sensation-weighting (SW) model, (b) can be generalized to successive and to simultaneous visual stimuli, and (c) vary, in accordance with the stimulus weighting, with interstimulus interval (ISI; for successive stimuli) or stimulus duration (for simultaneous stimuli). Participants compared paired successive jingles (Exp. 1), successive color patterns (Exp. 2), and simultaneous color patterns (Exp. 3), selecting the preferred stimulus. The results were well described by the SW model, which provided a better fit than did two extended versions of the Bradley-Terry-Luce model. Experiments 1 and 2 revealed higher weights for the second stimulus than for the first, and negatively valence-level-dependent TOEs. In Experiment 3, there was no laterality effect on the stimulus weighting and no valence-level-dependent space-order effects (SOEs). In terms of the SW model, the valence-leveldependent TOEs can be explained as a consequence of differential stimulus weighting in combination with stimulus valence varying from low to high, and the absence of valence-leveldependent SOEs as a consequence of the absence of differential weighting. For successive stimuli, there were no important effects of ISI on weightings and TOEs, and, for simultaneous stimuli, duration had only a small effect on the weighting.Keywords Aesthetic preference . Presentation order . Time-order errors . Space-order errors . Visual perception . Audition . Math modeling Fechner (1860) was the first to notice the ubiquitous and enigmatic systematic errors that occur in comparisons of successive and simultaneous stimuli, which make two physically equal stimuli subjectively different when compared: the Zeitfehler (time-order error) and the Raumfehler (spaceorder error). The time-order effect (TOE) and space-order effect (SOE) were defined as positive (vs. negative) for overestimation (vs. underestimation) of the first or left stimulus, respectively, relative to the second or right stimulus. Fechner (1876) also introduced experimental aesthetics, with scaling of aesthetic appreciation. However, he never combined those two subjects, which we attempt to do in the present article.Since Fechner's (1860) discovery, TOEs have been found for a wide range of modalities, including heaviness, tone loudness, line length, duration (see, e.g., Guilford, 1954;Hellström, 1985, for reviews), and brightness (Maeda, 1959).