In 2024, Psychometrika ran an unusual exchange. Three senior psychometricians — Klaas Sijtsma, Jules Ellis, and Denny Borsboom — published a focus article arguing that the humble sum score, the simple total of right-or-wrong answers on a test, is psychometrics’ greatest accomplishment and should remain central to practice. Two commentaries, …
A test item that scores differently for two groups of equally able examinees is called a differential item functioning (DIF) item, and identifying these items is now a routine part of large-scale assessment quality control. The hard part has never been the detection — statistical tests for DIF have been …
Lawrence T. DeCarlo’s recent article introduces a psychological framework for mixed-format exams, combining signal detection theory (SDT) for multiple-choice items and item response theory (IRT) for open-ended items. This fusion allows for a unified model that captures the nuances of each item type while providing insights into the underlying cognitive …
A 2024 study in Annals of Behavioral Medicine measured something most exercise-and-cognition research has not: not whether a structured exercise program improves brain function over weeks or months, but whether a single bout of everyday physical activity — walking the dog, climbing stairs, household chores — produces a measurable cognitive …
Multidimensional item response theory (MIRT) extends one-dimensional models like the 2PL or 3PL to test items that load on more than one latent trait. Once a model has more than one factor, the factor solution is not unique: any rotation of the factor axes produces an equivalent fit, so an …
When children from low-income backgrounds attend high-quality early childhood education programs, boys and girls show similar gains in IQ and reading by school entry. Where the picture changes is later. Long-term tracking of the Carolina Abecedarian Project — among the most rigorously studied early-childhood interventions in the world — shows …
Item response theory (IRT) parameters are not unique. Different parameterizations of the same model fit the data identically, and the choice between them is settled by convention rather than discovered from the data. The standard fixes — anchoring the latent-trait scale, fixing one item’s parameters, or imposing identification constraints during …
For a long time motor development and cognitive development were treated as parallel but mostly independent strands of children’s growth: motor skills tracked through pediatric milestones, cognitive skills tracked through psychometric assessments, and the two domains analyzed by separate researchers using separate frameworks. The past two decades of research have …
Calibrating a two-parameter logistic (2PL) item response theory model on a small or sparse dataset is a recurring practical problem. Maximum-likelihood estimators give unstable estimates with wide standard errors when there are few respondents per item, and they offer no principled way to share information across items or examinee subgroups. …
The heritability of intelligence is one of the most replicated findings in psychology — and one of the most consistently misunderstood. Six decades of twin and adoption studies, recently joined by genome-wide association studies on samples in the millions, converge on the conclusion that genetic differences explain a substantial fraction …
