IQ Gains in Early Schooling Fade

Children enrolled in Head Start or in another enriched preschool program, compared to similar children without such preschool, typically show a gain of about 10 IQ points during the year of the Head Start experience. This IQ gain typically fades and then disappears within the first few years of school, so that by second grade neither IQ nor achievement test scores nor¬ mally reveal any difference in performance between those children who had been in Head Start and those who had not been in...

 Alternative Reason for Age-Related Cognitive Decline

As adults age, their performance on many psychometric tests changes systematically, a finding that is widely taken to reveal that cognitive information-processing capacities decline across adulthood. Contrary to this, we suggest that older adults'; changing performance reflects memory search demands, which escalate as experience grows. A series of simulations show how the performance patterns observed across adulthood emerge naturally in learning models as they acquire knowledge. The simulati...

 Predictability and the Base Rate

Whenever a statistician wants to predict the likelihood of some event based on the available evidence, there are two main sources of information that have to be taken into account: (1) the evidence itself, for which a reliability figure has to be calculated; and (2) the likelihood of the event calculated purely in terms of relative incidence. The second figure here is the base rate. Since it is just a number, obtained by the seemingly dull process of counting, it frequently gets overlooked wh...

 The Danger of Measurement

Measurement has too often been the leitmotif of many investigations rather than the experimental examination of hypotheses. Mounds of data are collected, which are statistically decorous and methodologically unimpeachable, but conclusions are often trivial and rarely useful in decision making. This results from an overly rigorous control of an insignificant variable and a widespread deficiency in the framing of pertinent questions. Investigators seem to have settled for what is measurable ins...