demographic characteristics such as race and socioeconomic status." Reichman estimates that no more than 3 to 4% of the black–white IQ gap can be explained by black–white disparities in low birth weight. Education Several studies have proposed that a large part of the gap can be attributed to differences in quality of education. Racial discrimination in education has been proposed as one possible cause of differences in educational quality between races. According to a paper by Hala Elhoweris, Kagendo Mutua, Negmeldin Alsheikh and Pauline Holloway, teachers' referral decisions for students to participate in gifted and talented educational programs were influenced in part by the students' ethnicity. The Abecedarian Early Intervention Project, an intensive early childhood education project, was also able to bring about an average IQ gain of 4.4 points at age 21 in the black children who participated in it compared to controls. Arthur Jensen agreed that the Abecedarian project demonstrated that education can have a significant effect on IQ, but also declared his view that no educational program thus far had been able to reduce the black–white IQ gap by more than a third, and that differences in education are thus unlikely to be its only cause. A series of studies by Joseph Fagan and Cynthia Holland measured the effect of prior exposure to the kind of cognitive tasks posed in IQ tests on test performance. Assuming that the IQ gap was the result of lower exposure to tasks using the cognitive functions usually found in IQ tests among African American test takers, they prepared a group of African Americans in this type of tasks before taking an IQ test. The researchers found that there was no subsequent difference in performance between the African-Americans and white test takers. Daley and Onwuegbuzie conclude that Fagan and Holland demonstrate that "differences in knowledge between black people and white people for intelligence test items can be erased when equal opportunity is provided for exposure to the information to be tested". A similar argument is made by David Marks who argues that IQ differences correlate well with differences in literacy suggesting that developing literacy skills through education causes an increase in IQ test performance. A 2003 study found that two variables—stereotype threat and the degree of educational attainment of children's fathers—partially explained the black–white gap in cognitive ability test scores, undermining the hereditarian view that they stemmed from immutable genetic factors. Socioeconomic