Mental meeting of the sexes: boys' spatial advantage fades in poor families.

Time and again, researchers have found that males outperform females on spatial tasks, such as those that require mental rotation of objects and shapes. A new study indicates, however, that boys and girls from poor families don't display this well-established sex difference.

The new finding suggests that childhood experiences crucially influence the sexes' spatial abilities, say psychologist Susan C. Levine of the University of Chicago and her colleagues. In poor families, both boys and girls have little access to toys and activities that promote spatial skills, the scientists propose. In previous studies of middle- and upper-income families, boys spent more time on such activities than girls did.

"Even if there is a biological propensity for a male advantage in certain spatial tasks, there are lots of reasons to think that it is not fixed," Levine says.

The researchers studied 276 boys and 271 girls who began second grade in 1999 at any of 15 schools in and around Chicago. Children came from relatively wealthy, working-class, or poor families. Annual household incomes ranged from about $20,000, a level just above the federal poverty line for a family of four, to $125,000. More of the poor families were black than were families in the other two categories.

Each child completed three tasks in the fall and spring of the second and third grades. Two tasks involved spatial skills--finding a map location for a spot marked in an aerial photograph and mentally rotating pairs of figures to determine whether they fit together to form a square. On a third, nonspatial task, children were asked to select a picture described by a sentence read aloud.

Boys from upper- and working-class families consistently outperformed their female counterparts on both spatial tasks, the researchers report in the November Psychological Science. No sex difference in spatial scores appeared among kids from poor families, and both boys and girls scored lower than their counterparts in the other two groups did.

As the investigators expected, no sex difference emerged in sentence comprehension in any of the groups.

Earlier studies had shown that only in middle- and upper-income families do boys enjoy greater access to spatially geared toys, such as building blocks and video games. These boys also have more freedom to explore their neighborhoods, the scientists note.

Still, the new findings don't rule out an inherent but malleable male inclination toward spatial activities, Levine says.

"These data point to the importance of early experience [for spatial abilities]," comments psychologist Lynn S. Liben of Pennsylvania State University in University Park. "What is needed now is detailed observation of what it is that children from different backgrounds actually experience."

Levine's results indicate that in each economic group, especially high scorers on spatial tasks were usually boys, Liben notes. Similarly, earlier studies have found that more boys than girls achieve extremely high scores in mathematics.