yes, dear - :ihih: U told me to look over the definitions, & i did. a 'marker-Yes' is generally described as short & crisp, not "Yessss!". also, a whistle of S/S is the industry-standard for marine-mammal training, as is a thumbs-up for deaf-dogs; i've only seen one person use a starburst-hand to mark goal-behavior for a deaf-dog, usually it's one or another of the approval signals from ASL - American Sign Language, which U also might want to include. since consequences drive behavior, & the fact that the marker: click, flash, hand-sign, etc - predicts a reward is the salient clue to our learner of any species, i thought that should also be included in the definition. :001_smile: artificial language: an entirely-invented language, usually symbols, which can be used by non-humans to communicate with humans or non-humans conversant in the artificial language. see machine language. ASL: American Sign Language, a system of hand-signs which convey words or phrases, used to communicate by deaf-persons, or in very loud environs, or to communicate with non-humans. also see artificial language or machine language. machine language: an entirely-invented system of communication, usually symbols, used in research on the abilities & limits of non-human intelligence, thus far mostly in primates. see artificial language. EDIT: also, i think U missed 'Extinction' - the so-called 5th quadrant.