science-psychophysics: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/science-psychophysics - from package: science-psychophysics

You may install the required package with command apt-get install {package}

Error in other languages:
science-psychophysics: bevel nie gevind nie
science-psychophysics: comandă negăsită
science-psychophysics: comando não encontrado
science-psychophysics: commande introuvable
science-psychophysics: command not found
science-psychophysics: käsku ei ole
science-psychophysics: không tìm thấy lệnh
science-psychophysics: komanda nerasta
science-psychophysics: Kommando nicht gefunden.
science-psychophysics: kommandot finns inte
science-psychophysics: komut yok
science-psychophysics: nie znaleziono polecenia
science-psychophysics: níor aimsíodh an t-ordú
science-psychophysics: no se encontró la orden
science-psychophysics: no s'ha trobat l'ordre
science-psychophysics: opdracht niet gevonden
science-psychophysics: parancs nem található
science-psychophysics: perintah tidak ditemukan
science-psychophysics: príkaz nenájdený
science-psychophysics: příkaz nenalezen
science-psychophysics: команда не найдена
science-psychophysics: командата не е открита
science-psychophysics: 命令找不到
science-psychophysics: コマンドが見つかりません