The orangutans are learning to use a symbol-based language that is presented on a computer monitor. The monitor screen has large "buttons" that are big enough for orangutan fingers. The OLP dictionary contains a total of about 70 symbols. All symbols are abstract and have no visual relation to what they represent. In other words, the symbol for an apple looks nothing like an apple.
There are seven different categories of symbols and each category currently contains ten individual symbols. The symbol categories are:
Each category of symbols has its own specific exterior shape. For example, all food symbols have a rectangular exterior and all non-food object symbols have a circular exterior. A rectangle alone means "food" and a circle alone means "non-food object." Thus, each symbol can be broken down into its component parts just as a words are spelled using a series of letters. Individually, the interior components of each symbol are meaningless (like the letters of a word). It's the arrangement within the exterior shape that gives each symbol a specific meaning. In addition to the seven categories, there are symbols that mean "send," "clear," "yes/good," and "no/wrong."
The OLP dictionary can be expanded to as many symbols as the orangutans can learn. Currently, the orangutans are building their vocabularies. The next step will be to introduce syntax so that the individual symbols can be strung together to form simple sentences.
The orangutans participate in the OLP on a voluntary basis. There are no coercive or disciplinary elements to the program; orangutans are only reinforced with positive rewards. The animals are never coerced into working by being deprived of food, companionship, play time, or anything else.