the igbo language was used by john goldsmith as an example to justify deviating from the classical linear model of phonology as laid out in "the sound pattern of english". it is written in the roman script as well as the nsibidi formalized ideograms, which is used by the ekpe society and okonko fraternity, but is no longer widely used. nsibidi ideography existed among the igbo before the 16th century, but died out after it became popular among secret societies, who made nsibidi a secret form of communication. igbo language is difficult because of the huge number of dialects, its richness in prefixes and suffixes and its heavy intonation. igbo is a tonal language and there are hundreds of different igbo dialects and igboid languages, such as the ikwerre and ekpeye languages. in 1939, dr. ida c. ward led a research expedition on igbo dialects which could possibly be used as a basis of a standard igbo dialect, also known as "central igbo". this dialect included that of the owerri and umuahia groups, including the ohuhu dialect. this proposed dialect was gradually accepted by missionaries, writers, publishers, and cambridge university.