Release version 1.2.2 substantially increases computational efficiency by integrating R packages fastverse and Rfast and is compatible with R Statistical Computing Environment version 4.1. This release produces results nearly identical (see RMSE note below) to release version 1.0.0 used to conduct simulation analyses in the companion article. For most users, I recommend the latest release. For users preferring R package Tidyverse to fastverse, I recommend release version 1.1.0. Release Notes for Multi-observer Models version 1.2.2 Added R packages 'fastverse' and 'Rfast' to dependencies for simulation engine (DataS3) and example R code (DataS1) Optimized code to make use of efficient 'fastverse' and 'Rfast' functions in simulation engine and example R code Preferred matrices versus data frames for data analysis and data manipulation Added option to specify a random number seed in simulation input files (see DataS2) Updated example simulation file input file in DataS3 to include random number seed used to generate results Removed obsolete function 'psi.table.f' from 'supplemental_functions.r' For some models including covariates, corrected the sample size (sometimes off by 1) for computation of RMSE (root mean square error) for estimated overall mean true species probabilities ψ and overall mean classification probabilities θ. Changes to RMSE are minimal. Increased use of pipes to increase clarity of code Reduced dependence on package 'plyr' Edits to in-code documentation and supporting metadata files