@article{SchadVasishthHohensteinetal.2020, author = {Schad, Daniel and Vasishth, Shravan and Hohenstein, Sven and Kliegl, Reinhold}, title = {How to capitalize on a priori contrasts in linear (mixed) models}, series = {Journal of memory and language}, volume = {110}, journal = {Journal of memory and language}, publisher = {Elsevier}, address = {San Diego}, issn = {0749-596X}, doi = {10.1016/j.jml.2019.104038}, pages = {40}, year = {2020}, abstract = {Factorial experiments in research on memory, language, and in other areas are often analyzed using analysis of variance (ANOVA). However, for effects with more than one numerator degrees of freedom, e.g., for experimental factors with more than two levels, the ANOVA omnibus F-test is not informative about the source of a main effect or interaction. Because researchers typically have specific hypotheses about which condition means differ from each other, a priori contrasts (i.e., comparisons planned before the sample means are known) between specific conditions or combinations of conditions are the appropriate way to represent such hypotheses in the statistical model. Many researchers have pointed out that contrasts should be "tested instead of, rather than as a supplement to, the ordinary 'omnibus' F test" (Hays, 1973, p. 601). In this tutorial, we explain the mathematics underlying different kinds of contrasts (i.e., treatment, sum, repeated, polynomial, custom, nested, interaction contrasts), discuss their properties, and demonstrate how they are applied in the R System for Statistical Computing (R Core Team, 2018). In this context, we explain the generalized inverse which is needed to compute the coefficients for contrasts that test hypotheses that are not covered by the default set of contrasts. A detailed understanding of contrast coding is crucial for successful and correct specification in linear models (including linear mixed models). Contrasts defined a priori yield far more useful confirmatory tests of experimental hypotheses than standard omnibus F-tests. Reproducible code is available from https://osf.io/7ukf6/.}, language = {en} } @article{SorensenHohensteinVasishth2016, author = {Sorensen, Tanner and Hohenstein, Sven and Vasishth, Shravan}, title = {Bayesian linear mixed models using Stan: A tutorial for psychologists, linguists, and cognitive scientists}, series = {Tutorials in Quantitative Methods for Psychology}, volume = {12}, journal = {Tutorials in Quantitative Methods for Psychology}, publisher = {University of Montreal, Department of Psychology}, address = {Montreal}, issn = {2292-1354}, doi = {10.20982/tqmp.12.3.p175}, pages = {175 -- 200}, year = {2016}, abstract = {With the arrival of the R packages nlme and lme4, linear mixed models (LMMs) have come to be widely used in experimentally-driven areas like psychology, linguistics, and cognitive science. This tutorial provides a practical introduction to fitting LMMs in a Bayesian framework using the probabilistic programming language Stan. We choose Stan (rather than WinBUGS or JAGS) because it provides an elegant and scalable framework for fitting models in most of the standard applications of LMMs. We ease the reader into fitting increasingly complex LMMs, using a two-condition repeated measures self-paced reading study.}, language = {en} } @article{HohensteinKliegl2014, author = {Hohenstein, Sven and Kliegl, Reinhold}, title = {Semantic preview benefit during reading}, series = {Journal of experimental psychology : Learning, memory, and cognition}, volume = {40}, journal = {Journal of experimental psychology : Learning, memory, and cognition}, number = {1}, publisher = {American Psychological Association}, address = {Washington}, issn = {0278-7393}, doi = {10.1037/a0033670}, pages = {166 -- 190}, year = {2014}, abstract = {Word features in parafoveal vision influence eye movements during reading. The question of whether readers extract semantic information from parafoveal words was studied in 3 experiments by using a gaze-contingent display change technique. Subjects read German sentences containing 1 of several preview words that were replaced by a target word during the saccade to the preview (boundary paradigm). In the 1st experiment the preview word was semantically related or unrelated to the target. Fixation durations on the target were shorter for semantically related than unrelated previews, consistent with a semantic preview benefit. In the 2nd experiment, half the sentences were presented following the rules of German spelling (i.e., previews and targets were printed with an initial capital letter), and the other half were presented completely in lowercase. A semantic preview benefit was obtained under both conditions. In the 3rd experiment, we introduced 2 further preview conditions, an identical word and a pronounceable nonword, while also manipulating the text contrast. Whereas the contrast had negligible effects, fixation durations on the target were reliably different for all 4 types of preview. Semantic preview benefits were greater for pretarget fixations closer to the boundary (large preview space) and, although not as consistently, for long pretarget fixation durations (long preview time). The results constrain theoretical proposals about eye movement control in reading.}, language = {en} } @article{RisseHohensteinKliegletal.2014, author = {Risse, Sarah and Hohenstein, Sven and Kliegl, Reinhold and Engbert, Ralf}, title = {A theoretical analysis of the perceptual span based on SWIFT simulations of the n+2 boundary paradigm}, series = {Visual cognition}, volume = {22}, journal = {Visual cognition}, number = {3-4}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1350-6285}, doi = {10.1080/13506285.2014.881444}, pages = {283 -- 308}, year = {2014}, abstract = {Eye-movement experiments suggest that the perceptual span during reading is larger than the fixated word, asymmetric around the fixation position, and shrinks in size contingent on the foveal processing load. We used the SWIFT model of eye-movement control during reading to test these hypotheses and their implications under the assumption of graded parallel processing of all words inside the perceptual span. Specifically, we simulated reading in the boundary paradigm and analysed the effects of denying the model to have valid preview of a parafoveal word n + 2 two words to the right of fixation. Optimizing the model parameters for the valid preview condition only, we obtained span parameters with remarkably realistic estimates conforming to the empirical findings on the size of the perceptual span. More importantly, the SWIFT model generated parafoveal processing up to word n + 2 without fitting the model to such preview effects. Our results suggest that asymmetry and dynamic modulation are plausible properties of the perceptual span in a parallel word-processing model such as SWIFT. Moreover, they seem to guide the flexible distribution of processing resources during reading between foveal and parafoveal words.}, language = {en} } @article{KlieglHohensteinYanetal.2013, author = {Kliegl, Reinhold and Hohenstein, Sven and Yan, Ming and McDonald, Scott A.}, title = {How preview space/time translates into preview cost/benefit for fixation durations during reading}, series = {The quarterly journal of experimental psychology}, volume = {66}, journal = {The quarterly journal of experimental psychology}, number = {3}, publisher = {Wiley}, address = {Hove}, issn = {1747-0218}, doi = {10.1080/17470218.2012.658073}, pages = {581 -- 600}, year = {2013}, abstract = {Eye-movement control during reading depends on foveal and parafoveal information. If the parafoveal preview of the next word is suppressed, reading is less efficient. A linear mixed model (LMM) reanalysis of McDonald (2006) confirmed his observation that preview benefit may be limited to parafoveal words that have been selected as the saccade target. Going beyond the original analyses, in the same LMM, we examined how the preview effect (i.e., the difference in single-fixation duration, SFD, between random-letter and identical preview) depends on the gaze duration on the pretarget word and on the amplitude of the saccade moving the eye onto the target word. There were two key results: (a) The shorter the saccade amplitude (i.e., the larger preview space), the shorter a subsequent SFD with an identical preview; this association was not observed with a random-letter preview. (b) However, the longer the gaze duration on the pretarget word, the longer the subsequent SFD on the target, with the difference between random-letter string and identical previews increasing with preview time. A third patternincreasing cost of a random-letter string in the parafovea associated with shorter saccade amplitudeswas observed for target gaze durations. Thus, LMMs revealed that preview effects, which are typically summarized under preview benefit, are a complex mixture of preview cost and preview benefit and vary with preview space and preview time. The consequence for reading is that parafoveal preview may not only facilitate, but also interfere with lexical access.}, language = {en} } @article{HohensteinKliegl2010, author = {Hohenstein, Sven and Kliegl, Reinhold}, title = {Semantic preview benefit in eye movements during reading : a parafoveal fast-priming study}, issn = {0278-7393}, doi = {10.1037/A0020233}, year = {2010}, abstract = {Eye movements in reading are sensitive to foveal and parafoveal word features. Whereas the influence of orthographic or phonological parafoveal information on gaze control is undisputed, there has been no reliable evidence for early parafoveal extraction of semantic information in alphabetic script. Using a novel combination of the gaze- contingent fast-priming and boundary paradigms, we demonstrate semantic preview benefit when a semantically related parafoveal word was available during the initial 125 ms of a fixation on the pretarget word (Experiments 1 and 2). When the target location was made more salient, significant parafoveal semantic priming occurred only at 80 ms (Experiment 3). Finally, with short primes only (20, 40, 60 ms), effects were not significant but were numerically in the expected direction for 40 and 60 ms (Experiment 4). In all experiments, fixation durations on the target word increased with prime durations under all conditions. The evidence for extraction of semantic information from the parafoveal word favors an explanation in terms of parallel word processing in reading.}, language = {en} }