Using the mother's actions as a reference for object

British Journat of Developmental Psychology (1993), 11, 61-74

Printed in Creat Britain

,

61

© 1993 The British Psychological Society

Using the mother's actions as a reference for object exploration in 6- and 12-nionth-old infants Claes von Hofsten* and Anver Siddiqui* Department of Psychology, Vmea University, S-90187 Umea, Sweden

The questions asked in the present paper concern the role of the social context in the early devciopmenc of perception and action. How do infants acquire the various means of manual exploration and how do they get to apply these means appropriately to specific exploratory problems? An experiment is reported testing the possibility that infants learn these skills by observing adults doing tbem. Six-montbolds and 12-montb-olds were presented with four different objects whicb varied in form, size, texture, substance and sound potential. The subjects* mothers were also participants in the experiment and presented the objects to the infants after modelling a specific manipulation with it. Four different manipulations were modelled; banging, shaking, rubbing and rolling/sliding. Tbese actions were paired orthogonally with the four objects. Amount of manual activity in eacb condition was compared to an initial baseline at wbich the objects were presented to the child without modelling. It was found tbat infants selectively imitated the actions performed by adults on objects. For tbe same object, some bebaviours demonstrated by tbe mother were repeated mucb more frequently tban otbers. Finally, tbe implications for perceptual development of the idea tbat infants utilize their aduit surroundings for finding out about tbe world is discussed.

The questions asked in the present paper concern the role of the social context in the early development of perception and action. In what ways, if at all, will infants take advantage of the greater perceptual competence of adults in finding out about objects and events in their surroundings? This problem is applied here to the manual exploration of objects by infants. In order to perceive basic properties of objects such as substance (whether an object is rigid or not) and texture, manual exploration Is of great importance. How do infants acquire the various means of manual exploration and how do they get to apply these means appropriately to specific exploratory problems? There are several possible answers to this question. Certain perceived characteristics of objects could inherently afford certain actions and thus constrain the acquisition problem. For instance, a human voice evokes head-turning and looking towards the sound source even in the neonate (Field et al. 1980; Mendelson & Haith, * Requests for reprints can be addressed to either author.

62

Claes von Ho/sten and Anver Siddiqui

1976). Some of the fundamentals of reaching and grasping seem to belong to this group too. For instance, Hofsten & Spelke (1985) found that,, as successful reaching emerges, reaches are not primarily directed towards just any contours or surfaces. They are already from the start systematically directed towards such surfaces that constitute boundaries of perceived objects. Another determinant of the acquisition of exploratory skills is the interaction with the objects themselves. As the infant gets the object into his or her hand, the availability of haptic information about the object is contingent on various manual actions. Thus through manual exploration the infant learns to perceive significant properties of objects as well as learning about the exploratory procedures themselves. Learning to perceive through exploratory activity is clearly a major principle of perceptual developnient (Gibson, 1969, 1988). However, with nothing to guide this process, the search for information could be rather inefficient. This does not seem to be the case. Tnfants* exploratory manual actions get rapidly differentiated and appropriate at an early age (Lockman & McHale, 1989; Palmer. 1989; Ruff, 1984). Among other things, guidance by adults in exploring objects may help to explain this fact. The adults that make up the social context of the infant already know how to explore objects. If they, in the course of interaction with the infant, highlight some of these exploratory procedures, the infant may be able to short-cut the learning process. This is in line with Vygotsky (1978) who maintained that cognitive skills typically emerge in the context of social interaction. More specifically, he emphasized that cognitive development occurs in situations where the child is guided by interaction with an adult who provides structure to collaborative problem solving. As Rogoff, Mistry, Radziszewska & Germond (1991) would put it, infants use adults they are interacting with instrumentally in finding out about the world, and the adults aid children in these efforts. When applying these principles to object manipulation we would expect Infants with motor skills to exploit the greater exploratory and manipulatory skills of adults in learning how to find out about affordances of objects. We would also expect adults to highlight affordances of objects in their interaction with infants. Lockman & McHale (1989) found that this is indeed what is going on in adult-infant interaction. Mothers exhibited so much object-specific manipulatory behaviour in such a consistent and appropriate way when interacting with their infants that Lockman & McHale (1989) concluded that it constituted an additional source of information about objects. They also found that infants performed more focused exploration of the objects in the company of their mothers than when alone. As mentioned above, manual exploration of objects appears early in infancy and develops rapidly. As soon as infants begin reaching for and grasping objects successfully, they also begin exploring objects with eye and hand. Rochat (1989) found that between 3 and 4 months of age, infants started simultaneously to finger and look at objects. Steele & Pederson (1977) presented 6-month-olds with novel objects that differed from familiarized ones in terms of either shape or texture. The subjects increased the amount of manipulatory actions to both these kinds of changes suggesting that manipulation has useful exploratory functions at that age. Pedersen, Steele & Klein (1980) also found that some of the exploratory actions performed by 6-month-olds were specific to object properties. Lockman & McHale (1989) found

Mother's actions as a reference for object exploration that 6-month-old infants will adjust their behaviour in an appropriate way when exploring textured and coloured objects. These behaviours included touching, looking and rotating an object while looking. Tbey found that with textured objects, 6-month-oIds exhibited higher levels of fingering, rotation while looking and visual regard of object in hand. Coloured objects were also rotated more while looking but the fingering was not enhanced. However, not all object properties are equally well explored by 6-month-olds. Pedersen et al. (1980) found, for instance, that sound potential resulted in more touching, finger and hand movements but not in more shaking or banging. Lockman & McHale (1989) supported that finding. In their study 6-month-olds were not found particularly to bang or shake a soutiding object. In contrast to these results. Palmer (1989) found some tendency for 6-month-oids to wave a bell more if it had a clapper. Thus, appropriate actions on sound-making objects might start to emerge at that age but the behaviour does not seem to be firmly established. In the experiment to be reported, infants were presented with four different objects which varied in form, size, texture, substance and sound potential. The subjects' mothers were also participants in the experiment, presenting the objects to the infants after modelling a specific manipulation with them. Four different manipulations were modelled; banging, shaking, rubbing and rolling/sliding. These actions were paired orthogonally with the four objects. This design made it possible independently to evaluate the effect of object characteristics, modelling and the interaction between these two variables on the manipulatory behaviour of the infant. Six-month-old and 12-month-old infants were studied. The two age groups were chosen for the following reasons. Six-month-old infants were chosen because they have just mastered the basic manual movement patterns used in the present study (Hofsten, 1979). Twelve-month-old infants were chosen because it is known from other contexts (Klinnert, Compos, Sorce, Emde & Svedja, 1983) that infants of that age have the ability to use social referencing. Thus it is expected that the older infants at least would be able to utilize their mothers for finding out about objects.

I Method Subjects Nine 6-month-old (M= 184 days, range = 178-190) and nine 12-month-old infants (Af=363 days, range = 357-369) together with iheir mothers participated in the experiment. There were five girls and four boys among the 6-month-olds and four gids and five boys among the 12-month-olds. They were recruited through child-care centres. Three additional infants were excluded from the experiment, one due to the equipment failure, and two due to t'ussiness.

Materials Four small objects were selected for their range of form, size, substance, texture and sound potential. The four objects were: a large toy fish made of hard plastic with an uneven surface (16cm long, 7cm wide and 2 cm thick), a wooden rattle (about 6 by 4 em), an elastic, soft leather bal! (4.5 cm in diameter), a cloth doli (18 cm long). The objects were presented to the subjects on an adjustable board attached to a baby chair (see Fig. 1). The experiment was videotaped using two cameras with zoom lenses. One was focused on the infant and the other on the mother. The two pictures were fed into a video-recorder via a mixer, a digital clock giving the time on the video-screen in milliseconds.

63

64

Claes von Hofsten and Anver Siddiqui

Figure 1. The experitnental situation.

The behaviours modelled Four actions were selected to be modelled. They were chosen from the Uzgiris-Hunt Scale of Infant Assessment (1975) and the categories developed by Ruff (1984) as exploratory activities relevant to different object properties. Banging reveals information about the substance of objects and about the substance of the surface on which the object is banged, shaking reveals information about sound producing properties of an object, rubbing reveals information about surface properties, and moving an object over, a surface reveals information about friction between object and surface and whether the object could be rolled over the surface or not. bang;. The mother hit the object on the surface of the table in continuous up and down movements. Shake: The mother .shook the object in continuous up and down movements. Move: The mother rolled or moved the object over the table surface. Rub: The mother rubbed the object on some part of her body. Procedure Before the experiment the experimenter spent a short period talking to the mother in order to get her acquainted with the experimental procedure. The purpose of the study was explained to her, the objects to be used were shown, and tbe actions to be modelled were demonstrated. During this demonstration, the infant was clearly out of visual contact with the objects. The amount of time spent with each mother prior to observation was approximately 10 minutes.

Mother's actions as a reference for object exploration

65

The infant was then seated in the baby chair in front of which the adjustable board was attached. The board was adjusted so that the infant could easily reach and manipulate the objects on its surface. The mother was then seated in a chair, in front of her infant. The height of her chair was adjusted so that both mother and infant could maintain eye-contact easily. The objects were presented to the infant one at a time. Each trial lasted 30 seconds. The experiment was divided into three successive phases. In Phase 1, the mother jiist placed each object once in front of her infant without any modelling act and remained silent throughout the trial. This procedure was included to get an initial measure of how behaviours were distributed over objects in the absence of modelling. In Phase 2, the mother presented each of the four objects to her infant four times, each time demonstrating a specific manipulatory activity with the object before handing it over to the infant. Thus, this phase of the experiment consisted of 16 trials. The order between the 16 trials was randomized for each subject. Each demonstration took place outside the 30-second trial. The demonstrations were not formalized. The mother was simply asked to show her infant a specific behaviour performed on a specific object before handing it over to him or her. Each mother had her style of doing the demonstrations. In Phase 3, the mother again placed each object before the infant once without doing any modelhng act and remained silent throughout the presentation. In each phase, the order of the presentation was randomized. A list of the presentation order and the activity which was supposed to accompany each presentation was given to the mother before the experiment started. In cases where the infant fussed for 10 seconds or longer, the cameras were shut off until soothing was successful. Then, the cameras were again turned on and the interrupted trial repeated. The object was given hack to the infant if it was dropped once or twice, but if dropping was repeated more than twice, the next trial began. Measurement The four actions selected to be modelled were also coded. Bang and shake were coded as frequencies while move and rub were coded as durations. Bang and shake are discrete arcs and thus suitable to evaluate as frequency while rub and move are continuous behaviours and therefore preferably measured as durations. Bang: The infant hit the object on the surface of the table twice in one continuous up and down movement. Every time this happened one unit of behaviour was recorded. Shake: The infant shook the object at least twice in a continuous up and down movement. Every time this happened, one unit of behaviour was recorded. Move: The infant rolled or moved the object. Time in seconds was recorded. Kuh: The infant rubbed the object on some part of his or her body. Time in seconds was recorded. An additional four actions chosen from the U2giris-Hunt Scale of Infant Assessment (1975) and the categories developed by Rufi'(1984) were also monitored. For all these behaviours, time in seconds was recorded. These acts were chosen because they were relatively common and relatively welt known from earlier studes (Lockman, 1989; Palmer, 1989; Ruff, 1984). Look: The infant observed the object passively. Touch: The infant touched or held the object without looking at it. Rotate: The object was turned, rotated, or transferred from one hand to the other while the infant looked at it. Mouth: The objeet was put into the mouth. Intercoder agreement was calculated as percentage agreement on an action per subject across objects and maternal activities. The mean agreement for both age groups was over 88 per cent and overall concordance for actions was 95 per cent calculated on all subjects.

Results The modelled behaviottrs

The distribution of the four target behaviours (bang, shake, move and rub) over the four objects in the three phases of the experiment is shown in Figs 2 and 3. Banging

Claes von Hofsten and Anver Siddiqui

66

Fish

Ball

Doll

Rattle

Bang E P

B

E

P

B

E P

E P

B E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E P

B

E

8

P

B

Shake

Move

Rub

6-month-olds Figure 2. The distributioti of tbe modelled behaviours over objects for tbe 6-montb-oId Infants. Bang and Shake were measured as frequencies while Move and Rub were measured as duration (in seconds). The shadowed bars depict the effect of modelling {l\). The amount of each behaviour applied to each object in Phase 1 (baseline) and Phase 3 (post-test) are sbown in comparison. B is the amount of behaviour in Phase 1 and P is the amount of behaviour in Phase .1. The difference in the amount of behaviour between B and F, for each combination of behaviour and object were subject to / test. *;»