A Group of Infants Are Identified as Having Low IQs

Multiple Choice

A group of infants are identified as having low IQs, although it is admitted that infant IQ scores have low reliability. Five years later, most of these children have higher IQs than before. What is the most reasonable and most parsimonious conclusion?

A) The test that was given at the later time must have been easier than the first test.
B) The increase is due to random fluctuations in unreliable data.
C) IQ tests get better and better each year.
D) These children must have profited from some special experience they received during the 5-year delay.