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392 CHAPTER 9 Lifespan DevelopmentFigure 9.5 Testing Object Permanencein Babies How can you test object permanencein infants who are too young toreach for a hidden object? Three-anda-half-month-oldinfants initially watcheda possible event: The small carrot passesfrom one side of the panel to the otherwithout appearing in the window. In theimpossible event, the tall carrot does thesame. Because the infants are surprisedand look longer at the impossible event,Baillargeon and DeVos (1991) concludedthat the infants had formed a mental representationof the existence, height, andpath of each carrot as it moved behind thepanel—the essence of object permanence(Baillargeon, 2004).Figure 9.6 Infants Form Event-SpecificExpectations About the World SusanHespos and Renée Baillargeon (2001)found that 4 1 ⁄2-month-old infants respondwith increased attention when a tall objectcompletely disappears when placedbehind a shorter object (left) but notwhen a tall object disappears when placedinside a short container (right). It is notuntil the age of 7 1 ⁄2 months that infantsare also surprised by a tall container dis -appearing inside a short container. Accordingto Baillargeon (2004), such findingsdemonstrate that infants form eventspecificexpectations about the physicalworld rather than general principles.Possible EventImpossible EventFigure 9.5 shows one of Baillargeon’s classic tests of object permanence, conductedwith Julie DeVos (Baillargeon & DeVos, 1991). If the infant understandsthat objects continue to exist even when they are hidden, she will be surprised whenthe tall carrot unexpectedly does not appear in the window of the panel.Using variations of this basic experimental procedure, Baillargeon and her colleagueshave shown that infants as young as 2 1 ⁄2 months of age display object permanence(Aguiar & Baillargeon, 1999; Luo & others, 2003; Wang & others,2005). This is more than six months earlier than the age at which Piaget believedinfants first showed evidence of object permanence.Going beyond object permanence, Baillargeon and her colleagues have shownthat infants at different ages acquire different expectations about how the physicalworld operates. They’ve found that infants develop event-specific expectations, ratherthan general principles (Baillargeon, 2002, 2004).For example, the two events depicted in Figure 9.6 are similar in that both involvethe disappearance of a tall object. However, 4 1 ⁄2-month-old infants are surprised byone event—a tall object disappearing behind a short object—and not by the other—a tall object disappearing inside a short container (Hespos & Baillargeon, 2001, 2006).It’s not until 7 1 ⁄2 months of age that infants react with increased attention to theinside-container event. During infancy, it seems, each event is understood separately.Piaget’s discoveries laid the groundwork for our understanding of cognitivedevelopment. However, as developmental psychologists Jeanne Shinskey and YukoMunakata (2005) observe, today’s researchers recognize that “what infants appearto know depends heavily on how they are tested.”Criticism 2: Piaget underestimated the impact of the social and culturalenvironment on cognitive development. In contrast to Piaget, the Russian psychologistLev Vygotsky believed that cognitive development is strongly influencedby social and cultural factors. Vygotsky formulated his theory of cognitive developmentat about the same time as Piaget formulated his. However, Vygotsky’s writingsdid not become available in the West until many years after his untimely deathfrom tuberculosis in 1934 (Rowe & Wertsch, 2002; van Geert, 1998).Vygotsky agreed with Piaget that children may be able to reach a particular cognitivelevel through their own efforts. However, Vygotsky (1978, 1987) argued thatchildren are able to attain higher levels of cognitive development through the support4.5 months 7.5 monthsBehind Short ContainerInside Short Container