According to research noted in your textbook, children as young as year(s) of age already demonstrate a preference for different types of toys, even if they have been exposed only to gender-neutral toys or have had equal access to toys commonly associated with both genders.

According to research noted in your textbook, children as young as one year(s) of age already demonstrate a preference for different types of toys,

Explanation:

Researchers have shown that by age one* , children show clear preferences for gender-consistent toys (eg trucks for boys, dolls for girls). This occurs even if they have only been exposed to gender-neutral toys, or had equal access to both “boys” and “girls” toys.

*G. Alexander, J Saenz,  Early androgens, activity levels and toy choices of children in the second year of life, Hormones and Behavior 62(4):500-4

i have to go with a for this one