All of the following statements about 'Imbecile' are true, EXCEPT:

Imbeciles have an IQ of 25 to 49 and a mental age of 3-7 years. They have impaired and this intellectual disability is usually congenital or acquired at an early age. Intelligence quotient( IQ), is obtained by dividing the subject's mental age (as determined by the Binet-Simon scale) by his chronologic age (up to the 14th year) and multiplying the result by 100. IQ increases with age up to 14th to 16th years and then remains stable, at least until late adult life. Level of intelligence according to IQ Idiot < 25 Imbecile 25-50 Moron 50-70 Borderline defective 70-80 Low normal 80-90 Normal 90-110 High average 110-120 Superior Very superior 120-140 >140 Ref: Park 20th edition, page 592; Introduction to Psychology By J.mahmud, page 236; Current Diagnosis & Treatment: Psychiatry, 2e chapter 31.