NEW YORK (AP) _ English children have shown an ''appreciable rise'' in average IQ over the past 50 years, a study says.

When an IQ test was given to 1,029 school children ages 9-11 in 1985, their average score was 12.42 points higher than the 1935 average of 100 points, researchers wrote.

The ''Cattell Non-Verbal'' test measures ''fluid intelligence,'' the mental power used to learn thinking skills, rather than the levels of those skills themselves, said Richard Lynn and colleagues from the University of Ulster.

The test presents problems in pictures and diagrams and minimizes influence of racial, ethnic and educational differences, they wrote in Thursday's issue of the British journal Nature.

The gain averaged 2.48 points per decade. A recent 14-nation survey suggested that Britain's rise was less than 2 points per decade, lagging behind that of other economically advanced nations, the researchers said.

The studies cited for Britain span the years of World War II, researchers wrote. The new study found an increase of only about 0.75 points per decade during 1935-49, jumping to 3.16 points per decade from 1949 to 1985.

So Britain's showing in the 14-nation survey stems from the slowing in the war years, they concluded. The post-war gain ''is within the normal range for other economically advanced nations,'' which is 2 points to 12 points per decade, they said.

In an accompanying editorial, psychologist Chris Brand of the University of Edinburgh said the newly measured gains may reflect ''lowered levels of caution, conscientiousness and conservatism of social attitudes.'' Such changes may affect scores on tests like the one in the study, he said.