It is demonstrated that the popular three-parameter logistic model can lead to markedly inaccurate individual ability level estimates for mixture populations. A theoretically and empirically important setting is initially considered where (a) in one of two subpopulations (latent classes) the two-parameter logistic model holds for each item in a…

The term speed-accuracy tradeoff is used when an increase in response speed comes at the expense of response accuracy. Although originally a concept from experimental psychology, the speed-accuracy tradeoff has been a topic in psychological assessment, too. In the first part of the manuscript, we discuss motivational factors that may be…

A new and very interesting approach to the analysis of responses and response times is proposed by Goldhammer (this issue). In his approach, differences in the speed-ability compromise within respondents are considered to confound the differences in ability between respondents. These confounding effects of speed on the inferences about ability can…

The excellent paper by Goldhammer (this issue) deals with a most relevant and very pervasive problem of ability assessment: the evaluation of performance by considering speed and accuracy of performance. Goldhammer proposes item-level time limits as a possible remedy for individual differences in the speed-accuracy trade-off (SATO) to keep time…

Research into executive functioning (EF) has indeed grown exponentially across the past few decades, but as the Willoughby et al. critique makes clear, there remain fundamental questions to be resolved. The crux of their argument is built upon an examination of the confirmatory factor analysis (CFA) approach to understanding executive processes.…

The main challenge of ability tests relates to the difficulty of items, whereas speed tests demand that test takers complete very easy items quickly. This article proposes a conceptual framework to represent how performance depends on both between-person differences in speed and ability and the speed-ability compromise within persons. Related…

This article describes an exploration of the distinction between typological and factorial latent variables in the domain of personality theory. Traditionally, many personality variables have been considered to be factorial in nature, even though there are examples of typological constructs dating back to Hippocrates. Recently, some…

Nesselroade, Gerstorf, Hardy, and Ram developed a new and interesting way to enforce invariance at the second-order level in P-technique models, while allowing first-order structure to stray from invariance. We discuss our concerns with this approach under the headings of falsifiability, the nature of manifest variables included in models, and…

Nesselroade, Gerstorf, Hardy, and Ram (this issue) propose to "filter out" idiosyncrasies of dynamic processes at the level of the individual through the application of dynamic factor analysis. The problem that they deal with is that individuals may differ in the items that are "salient" for a given construct, so that the same measurement model…

Nomothetic and idiographic approaches to research have long been in tension. John Nesselroade et al. have been at the forefront of a constructive rapprochement between these traditions. Heretofore their efforts have assumed a common measurement structure across persons. They have primarily focused on modeling relationships within persons, which…

Ideally, the unit of analysis in psychology is the individual. However, many psychological methods do not cope well, either at the level of construct definition or at the level of measurement, with individuality in behavior. There is little leeway for constructs to be both idiosyncratically tailored to the individual, and still identified as…

In this article, the authors comment on Nesselroade, Gerstorf, Hardy, and Ram's efforts (this issue) to grapple with the challenge of accommodating idiographic assessment as it pertains to measurement invariance (MI). Although the authors are in complete agreement with the motivation for Nesselroade et al.'s work, the authors have concerns about…

This article presents a rejoinder to Rogosa's (2004) commentary on the author's (Molenaar, 2004) focus article titled, "A Manifesto on Psychology as Idiographic Science." The expert commentary of Rogosa brings up some central issues that require careful evaluation. The basic message of the author's focus article was straightforward: In general,…