Infants older than six months can retain information for longer periods of time; they also need less reminding to retrieve information in memory. Studies of deferred imitation, that is, the imitation of actions after a time delay, can occur as early as six months (Campanella and Rovee-Collier, 2005), but only if infants are allowed to practice the behaviour they were shown. By twelve months, infants no longer need to practice the behaviour in order to retain the memory for four weeks (Klein and Meltzoff, 1999).
34 Infant Memory
Martha Lally and Suzanne Valentine-French
Memory requires a certain degree of brain maturation, so it should not be surprising that infant memory is rather fleeting and fragile. As a result, older children and adults experience infantile amnesia, the inability to recall memories from the first few years of life. Several hypotheses have been proposed for this amnesia. From the biological perspective, it has been suggested that infantile amnesia is due to the immaturity of the infant brain, especially those areas that are crucial to the formation of autobiographical memory, such as the hippocampus. From the cognitive perspective, it has been suggested that the lack of linguistic skills of babies and toddlers limit their ability to mentally represent events; thereby, reducing their ability to encode memory. Moreover, even if infants do form such early memories, older children and adults may not be able to access them because they may be employing very different, more linguistically based retrieval cues than infants used when forming the memory. Finally, social theorists argue that episodic memories of personal experiences may hinge on an understanding of self, something that is clearly lacking in infants and young toddlers.
However, in a series of clever studies, Carolyn Rovee-Collier and her colleagues have demonstrated that infants can remember events from their life, even if these memories are short-lived. Three-month-old infants were taught that they could shake a mobile hanging over their crib by kicking their legs. The infants were placed in their crib on their backs. A ribbon was tied to one foot and the other end to a mobile. At first infants made random movements, but then came to realize that by kicking they could make the mobile shake. After two 9-minute sessions with the mobile, the mobile was removed. One week later the mobile was reintroduced to one group of infants and most of the babies immediately started kicking their legs, indicating that they remembered their prior experience with the mobile. A second group of infants was shown the mobile two weeks later and the babies made only random movements; the memory had faded (Rovee-Collier, 1987; Giles and Rovee-Collier, 2011). Rovee-Collier and Hayne (1987) found that 3-month-olds could remember the mobile after two weeks if they were shown the mobile and watched it move, even though they were not tied to it. This cue helped most infants remember the connection between their kicking and the movement of the mobile. Like many researchers of infant memory, Rovee-Collier (1990) found infant memory to be context dependent. In other words, the sessions with the mobile and the later retrieval sessions had to be conducted under very similar circumstances or else the babies would not remember their prior experiences with the mobile. For instance, if the first mobile had yellow blocks with blue letters, but at the later retrieval session the blocks were blue with yellow letters, the babies would not kick.