rtprep: Screening, Trimming, and Aggregating Response Time Data

Tools for the decisions made about response times before a model is fitted: which trials to keep, how to summarise the ones that survive, and how to check what either choice did.

The screening rules come from families that were never built to be compared: absolute cutoffs, criteria based on a centre and a spread, the recursive criteria, a control chart on accuracy, a fitted contaminant mixture. Every published implementation returns something different. Here they all return one row per trial with the same four columns, so swapping one for another is a one-word change and the difference between them can be measured.

The four layers

Screening

rt_screen() applies a rule and returns the keep decision, the probability behind it, and the reason. rt_keep() gives the decision alone for filter(); screen_fits() gives the per-group diagnostics. The rules are in rules, and rule_all() and its companions combine them.

Aggregation

rt_summary() turns surviving trials into the mean, variance and accuracy the EZ-diffusion equations take, by sample moments, robust moments, trimming, or a fitted mixture. ez_ddm() inverts them into parameters; adjust_accuracy() corrects the counts.

Comparison

screen_compare() applies several rules at once and reports how much each removed and how far they disagree. check_guessing() asks whether the fast trials a rule removed were really guesses.

Ground truth

r_contaminated() generates response times with contaminants labelled, and rule_oracle() removes exactly those, which is the ceiling every real rule is read against.

Two things that hold everywhere

.prob is always the probability that a trial came from the decision process, never the probability that it is a contaminant, and the keep decision is a separate step. A deterministic rule returns 0 and 1; a mixture returns a posterior; both can feed rt_summary(weights = ) without a threshold being chosen.

A rule that cannot be evaluated removes nothing: too few trials, zero spread or a fit that did not converge keeps every trial in the group and records why in screen_fits(). extending states the contract that follows from.

Terms

See rtprep-glossary for contaminant, drift, bound, ndt, leading edge, and the difference between screening, trimming and aggregation.

See also

vignette("rtprep") for the whole chain on one data set; extending to add a rule of your own.

Author

Maintainer: Gidon T. Frischkorn gidon.frischkorn@psychologie.uzh.ch (ORCID) [copyright holder]