Pseudo is a program that generates nonwords from a list of words by randomly substituting one or more letters, transposing two letters, or by adding/inserting/deleting one or more letters. Multiple constraints (e.g., minimum bigram or trigram frequency) can be applied so that the generated nonwords become word-like strings that are more likely pronounceable (i.e., pseudowords). Furthermore, generated nonwords can be checked against one or more lexicons to make sure that it is not an actual word in a language.
Pseudo also automatically checks whether a newly generated nonword is already in the list of generated nonwords. When the program is unable to generate a nonword (e.g., due to strict constraints), it adds a "<" and ">" around the source string and copies this to the list of nonwords. The program can also generate all possible nonwords from a single letter string. First, enter a single letter string as source and then select "Generate all nonwords" in the menu "Generate".
The program calculates (position specific and position non-specific) letter, bigram, and trigrams frequencies from a word frequency database (e.g., SUBTLEX-UK) and these can be used to generate more word-like nonwords. The lexicon file format needs to be plain text (e.g., ASCII, UTF8 format) with two columns separated by a space or tab. The first column should contain words and the second column word frequencies. Letter, bigram and trigram frequencies (type/tokens) can be viewed in the program and saved to a text file.
Pseudo can generate nonwords in alphabetic and non-alphabetic languages. Vowels and consonants are provided for many languages and the character sets of non-alphabetic languages can be imported into the program.
Downloads
Latest version: 2.60
- macOS (Apple Silicon) (M1 or later, DMG)
- macOS (Intel) (DMG)
- Windows (x64) (Windows Intel/AMD installer)
- Windows (ARM64) (Windows ARM64 installer)
Recent changes
- Added more writing systems.
- A frequency list can be created from text files.
- GUI improvements and font fixes.
Please note that the apps/installers are not notarized. To open the app on macOS follow the instructions on this page, see section: How to open an app that hasn’t been notarized or is from an unidentified developer.
Disclaimer
Pseudo is provided “as is”, without warranty of any kind, express or implied. To the fullest extent permitted by law, the author shall not be liable for any claim, loss, damage or other liability arising from the software or its use.
Citation
If you use Pseudo in your research, please cite it as follows:
van Heuven, W. J. B. (2026). Pseudo (Version 2.60) [Computer software]. https://waltervanheuven.net/pseudo/