The A not B Task

Emilie sits on her father's lap and excitedly stares at the shiny brass bell that the research assistant across the table is holding. Making sure Emilie is watching, the assistant places the bell into one of two matching wells in the table and then quickly covers both wells with identical cloths. Emilie is eager to grab the bell, as any eight-month-old would, but her father gently holds back her arms while the researcher distracts her with a funny face. After five seconds, Dad is signaled to ...