ANCHOR Model Implementation

This archive contains Matlab software implementing the ANCHOR model of category rating and absolute identification. A comprehensive list of ANCHOR publications is available from my publication page. The defining article is:

Petrov, A. & Anderson, J. R. (2005)
The Dynamics of Scaling: A Memory-Based Anchor Model of Category Rating and Absolute Identification. Psychological Review, 112(2), 383-416.
Abstract Reprint (pdf)

Contents of This Package

The main directory contains the implementation of the ANCHOR model itself (anchor2.m) as well as a model-tracking version (anchor2mt.m) for parameter fitting (Petrov, 2001).

The finalsim directory provides tools for analysing the stimulus-response sequences generated by the model and comparing them to human data. The finalsim/hier directory contains the simulation results with a hierarchy of nested models on a battery of measures of various phenomena. These results are reported in Table 4 of Petrov & Anderson (2005) and are provided here as a research-grade example of how to use the ANCHOR software.

The utils directory and its subdirectory contains a library of utilities used by the model code. See the Contents.m files in these respective directories for a list of the individual files and for examples of their use. Each .m file contains extensive comments too.

Finally, finalsim/hier directory contains several transcripts (*.txt files), scripts (.m), and data (.mat) taken during the development and fitting of the model. Use them as guidance.

ANCHOR was developed and run on Matlab ver (R11) for Windows. The implementation ported flawlessly to Matlab 7.2 (R2006b) for Mac OS X. It depends on my UTILS Toolbox distributed free under the terms of the GNU GPL. The relevant utilities are included in the, although newer versions may be available from my software page. The parameter search routines depend on Matlab's stats and optim Toolboxes, although the stats dependency probably is minimal.

For a basic installation, simply unzip the archive in a directory of your choice and add anchor and utils/general to Matlab's path. To fit parameters, the path should also include utils/paramsearch, utils/regression, and anchor/finalsim. See Contents.m for specific examples. There are also examples in many of the individual .m files.

Please notify me of any bugs, notes, comments or suggested changes, particularly of any useful changes you may have made to your own copy of the software.

Thank you for your interest in ANCHOR. Happy modeling!


This software is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License and the Free Software Foundation for more details.

The software is freely available and freely redistributable, according to the conditions of the GNU General Public License. You may not distribute the software, in whole or in part, in conjunction with proprietary code. That means you only have my permission to distribute a program that uses my code if you also make freely available (under the terms of the GNU GPL) the source code for your whole project. You may not pass on the software to another party in its current form or any altered, embellished or reduced form, without acknowledging the author, citing Petrov & Anderson (2005), and including a copy of the GNU GPL. Check the validity of this page's XHTML Check the validity of this site's Cascading Style Sheet Page maintained by Alex Petrov
Created 2007-03-30, last updated 2007-03-30.