individuals often modify their behavior based on what they have learned about the possible consequences of their actions

修饰的是individuals often modify their behavior这句话.
语法上修饰哪个都可能,但语义上明显是修饰这句话的：
人们在知道了自己的行为会导致什么后果之后,常常会据此修改他们的行为.
如果是修饰behavior一个词,那么意思是：
人们经常会修改这样的行为,即：以了解到的可能产生的后果为基础（或依据）的行为.
不仅逻辑不通,而且behavior的单复数也有点问题.那individuals often modify their behavior这句话在是作主语么？individuals是主语；modify 是谓语；their behavior 是宾语；based on what they have learned about the possible consequences of their actions是状语。