Object play and problem solving in infancy: Insights into tool use.

Tool use is primarily, but not exclusively, present in species with otherwise advanced cognitive traits. However, the interaction between such traits and conspecific inter-individual variation in the presence, complexity, or intensity of tool use is far from being established. We addressed this matter among human infants, seeking factors that relate to differences in tool use. We examined, both correlationally and experimentally, whether the propensity to engage in object combinations predicts performance in means-end problem-solving tasks involving or not involving the use of a tool. We tested 71 infants aged 15, 18, 21, and 24 months, dividing them into two subgroups: one exposed to an adult demonstrating object-object combinations (i.e., "prompting" infants to combine objects together) and another with comparable social exposure but where the adult demonstrated single-object manipulations. We found a correlation between the combined level of spontaneous and prompted object combinations and problem-solving performance regardless of the involvement of tools in the problem. However, we did not find differences in tool-use performance between the two demonstration subgroups. The correlational analysis suggests that complexity of play, as measured by the frequency of combining objects, is linked to infants' problem-solving skills rather than being specifically associated with tool use, as previously suggested in the literature.

Humour production may enhance observational learning of a new tool-use action in 18-month-old infants.

Many studies have shown that making children laugh enhances certain cognitive capacities such as attention, motivation, perception and/or memory, which in turn enhance learning. However, no study thus far has investigated whether laughing has an effect on learning earlier in infancy. The goal of this study was to see whether using humour with young infants in a demonstration of a complex tool-use task can enhance their learning. Fifty-three 18-month-old infants participated in this study and were included either in a humorous or a control demonstration group. In both groups infants observed an adult using a tool to retrieve an out-of-reach toy. What differed between groups was that in the humorous demonstration group, instead of playing with the toy, the adult threw it on the floor immediately after retrieval. The results show that infants who laughed at the demonstration in the humorous demonstration group reproduced significantly more frequent target actions than infants who did not laugh and those in the control group. This effect is discussed with regard to individual differences in terms of temperament and social capacities as well as positive emotion and dopamine release.

Handedness in infants' tool use.

In this study, we investigated whether hand preference influences infants' choice of what hand to use in grasping a new tool presented at the midline, and whether this will change in the course of learning the functionality of a tool. The tool was a rake within reach placed beside an out-of-reach toy presented either to its right or to its left. Forty-eight infants from 16 to 22 months of age were tested. The results show that use of the right-preferred hand to grasp the rake is strong as of 16 months of age and does not change significantly with age in the condition where using the right hand leads to a better outcome than using the left hand. In the condition where using the left-non-preferred hand makes toy retrieval easier, infants increasingly use the left hand with age. Thus, when grasping the tool, younger infants are more influenced by their hand preference than older infants, who are better at anticipating the most successful strategies.

The emergence of tool use during the second year of life.

Despite a growing interest in the question of tool-use development in infants, no study so far has systematically investigated how learning to use a tool to retrieve an out-of-reach object progresses with age. This was the first aim of this study, in which 60 infants, aged 14, 16, 18, 20, and 22 months, were presented with an attractive toy and a rake-like tool. There were five conditions of spatial relationships between the toy and the tool, going from the toy and tool being connected to there being a large spatial gap between them. A second aim of the study was to evaluate at what age infants who spontaneously fail the task can learn this complex skill by being given a demonstration from an adult. Results show that even some of the youngest infants could spontaneously retrieve the toy when it was presented inside and touching the top part of the tool. In contrast, in conditions with a spatial gap, the first spontaneous successes were observed at 18 months, suggesting that a true understanding of the use of the tool has not been fully acquired before that age. Interestingly, it is also at 18 months that infants began to benefit from the demonstration in the conditions with a spatial gap. The developmental steps for tool use observed here are discussed in terms of changes in infants' ability to attend to more than one item in the environment. The work provides insight into the progressive understanding of tool use during infancy and into how observational learning improves with age.

Pigeons discriminate between human feeders.

Considered as plague in many cities, pigeons in urban areas live close to human activities and exploit this proximity to find food which is often directly delivered by people. In this study, we explored the capacity of feral pigeons to take advantage of this human-based food resource and discriminate between friendly and hostile people. Our study was conducted in an urban park. Pigeons were fed by two experimenters of approximately the same age and skin colour but wearing coats of different colours. During the training sessions, the two human feeders displayed different attitudes: one of the feeders was neutral and the second was hostile and chased away the pigeons. During the two test phases subsequent to the training phase, both feeders became neutral. Two experiments were conducted, one with one male and one female feeder and the second with two female feeders. In both experiments, the pigeons learned to quickly (six to nine sessions) discriminate between the feeders and maintained this discrimination during the test phases. The pigeons avoided the hostile feeder even when the two feeders exchanged their coats, suggesting that they used stable individual characteristics to differentiate between the experimenter feeders. Thus, pigeons are able to learn quickly from their interactions with human feeders and use this knowledge to maximize the profitability of the urban environment. This study provides the first experimental evidence in feral pigeons for this level of human discrimination.

The Emergence of Tool Use in Preterm Infants.

Preterm born children without neurological impairments have been shown to present some visual-manual coordination deficits, more or less depending on their tonicity and the degree of prematurity. In this paper, we compare the development of tool use in 15-23-month-old preterm infants born after 33-36 weeks of gestation without neurological complications with that of full-term infants according to corrected age. Understanding the affordance of a tool is an important cognitive milestone in early sensorimotor period. Using a tool to bring within reach an out-of-reach object, for instance, has been shown to develop during the 2nd year in full-term infants. Here we presented preterm infants with an attractive toy out of reach and with a rake-like tool within reach in five conditions of spatial relationships between the toy and the tool. Like full-terms, preterm infants used the tool with success in conditions of spatial contiguity around 15-17 months. In conditions of a spatial gap between tool and toy, i.e., the only conditions which shows without ambiguity that the infant understands the affordance of the tool, preterm infants as a group showed no delay for tool use: the frequency of spontaneous successes started to increase after 18 months, and demonstration became effective after that age. However, further analyses showed that only the preterm infants without hypotonia and born after 36 weeks of pregnancy developed tool use without delay. Hypotonic preterm infants were still largely unsuccessful in the conditions of spatial gap, even at the end of the study. The degree of prematurity also influenced the performance at tool use. These results, following the observation of a delay in the development of bimanual coordination and of handedness in the same infants at 10-12 months in a previous study, show that low risk preterm infants can still be impaired for the development of new manual skills beyond the 1st year. Thus, hypotonic preterm infants and infants born before 36 weeks of pregnancy should be followed and might benefit from early intervention programs.

What Does It Take for an Infant to Learn How to Use a Tool by Observation?

Observational learning is probably one of the most powerful factors determining progress during child development. When learning a new skill, infants rely on their own exploration; but they also frequently benefit from an adult's verbal support or from demonstration by an adult modeling the action. At what age and under what conditions does adult demonstration really help the infant to learn a novel behavior? In this review, we summarize recently published work we have conducted on the acquisition of tool use during the second year of life. In particular, we consider under what conditions and to what extent seeing a demonstration from an adult advances an infant's understanding of how to use a tool to obtain an out-of-reach object. Our results show that classic demonstration starts being helpful at 18 months of age. When adults explicitly show their intention prior to demonstration, even 16-month-old infants learn from the demonstration. On the other hand, providing an explicit demonstration ("look at how I do it") is not very useful before infants are ready to succeed by themselves anyway. In contrast, repeated observations of the required action in a social context, without explicit reference to this action, considerably advances the age of success and the usefulness of providing a demonstration. We also show that the effect of demonstration can be enhanced if the demonstration makes the baby laugh. Taken together, the results from this series of studies on observational learning of tool use in infants suggest, first, that when observing a demonstration, infants do not know what to pay attention to: demonstration must be accompanied by rich social cues to be effective; second, infants' attention is inhibited rather than enhanced by an explicit demand of "look at what I do"; and finally a humorous situation considerably helps infants understand the demonstration.

When do infants understand that they can obtain a desired part of a composite object by grasping another part?

When do infants start to understand that they can grasp an object by its handle when the interesting part is out of reach? Whereas it is known from preferential looking tasks that already at three months of age infants show surprise when all parts of an object do not move together, little is known about when infants are able to use such knowledge in an active grasp situation. To answer this question we presented six, eight, and 10 month-old infants in a cross-sectional and a longitudinal study with a white cardboard handle within reach and a bright ball at the end of the handle and out of reach. A trick condition, where the handle and the ball seem attached but were not, was added to get an indication of the infant's expectation by observing a possible surprise reaction. Results show that 6-month-olds' most frequent first behaviors consisted in pointing toward the ball without grasping the handle, or grasping the handle without looking at the ball until it moved. In addition, they often did not look surprised in the trick condition. Eight- and 10-month-olds most often grasped the handle while looking at the ball, and showed clear surprise in the trick condition. This was interpreted as showing that around eight or 10 months, infants take a significant step in understanding the cohesiveness of composite objects during grasping.

The emergence of use of a rake-like tool: a longitudinal study in human infants.

We describe the results of a longitudinal study on five infants from age 12 to 20 months, presented with an out of reach toy and a rake-like tool within reach. Five conditions of spatial relationship between toy and rake were tested. Outcomes and types of behavior were analyzed. There were successes observed around 12 months in the condition of spatial contiguity between rake and toy, but these could not be interpreted as corresponding to full understanding of the use of the rake. At this age and for the following months, in the conditions involving spatial separation between rake and toy, infants' strategies fluctuated between paying attention to the toy only, exploring the rake for its own sake, and connecting rake and toy but with no apparent attempt to bring the toy closer. Only between 16 and 20 months did infants fairly suddenly start to intentionally try to bring the toy closer with the tool: at this stage the infants also became able to learn from their failures and to correct their actions, as well as to benefit from demonstration from an adult. We examine the individual differences in the pattern of change in behaviors leading to tool use in the five infants, and find no increase in any one type of behavior that systematically precedes success. We conclude that sudden success at 18 months probably corresponds to the coming together of a variety of capacities.

Comparison of active and purely visual performance in a multiple-string means-end task in infants.

The aim of the present study was to understand what factors influence infants' problem-solving behaviours on the multiple-string task. The main question focused on why infants usually solve the single string-pulling task at 12months at the latest, whereas most 16-month-old infants still cannot solve the task when several strings are presented, only one of which is attached to the desired object. We investigated whether this difficulty is related to infants' ability to inhibit their spontaneous immediate actions by comparing active and purely visual performance in this task. During the first part of the experiment, we assessed the ability of infants aged 16-20months to solve the multiple-string task. The infants were then divided into three groups based on performance (a "failure" group, an "intermediate" group, and a "success" group). The results of this action task suggest that there were differences in infants' performance according to their level of inhibitory control of their preferred hand. In the second part of the experiment, the three groups' predictive looking strategies were compared when seeing an adult performing the task. We found that only infants who successfully performed the action task also visually anticipated which string the adult had to pull in the visual task. Our results suggests that inhibitory control was not the only factor influencing infants' performance on the task. Furthermore, the data support the direct matching hypothesis (Rizzolatti and Fadiga, 2005), according to which infants need to be able to perform actions themselves before being able to anticipate similar actions performed by others.