The multidimensional log-normal response time model: An exploration of the multidimensionality of latent processing speed

With the popularity of computer-based testings, the collection of item response times (RTs) and other process data has become a routine in large- and small-scale psychological and educational assessments. RTs not only provide information about the processing speed of respondents but also could be utilized to improve the measurement accuracy because the RTs are considered to convey a more synoptic depiction of the participants’ performance beyond responses alone. In multidimensional assessments, various skills are often required to answer questions. The speed at which persons were applying a set of skills reflecting distinct cognitive dimensions could be considered as multidimensional as well. In other words, each latent ability was measured simultaneously with its corresponding working efficiency of applying a facet of skills in a multidimensional test. For example, the latent speed corresponding to the latent ability of decoding of an algebra question may differ from encoding. Therefore, a multidimensional RT model is needed to accommodate this scenario, which extends various currently proposed RT models assuming unidimensional processing speed.