This clip shows how an infant is tested on ERP (here with an EGI Geodesic Sensor Net system). In an ERP study a net of sensors is placed on the infant’s head to measure the electric activity generated by neurons in the brain. In a first step the circumference of the infant’s head is measured so that the right size net can be applied. The selected net is then soaked in a saline solution for five minutes to ensure good conductivity when it is placed on the head. In placing the net on the infant’s head the researcher has to be very skilled and fast. Infants over one year of age are very lively and often want to pull down the net and see what it is. In the video all works well, though, and we can see the recorded EEG signal on the control monitor. Large oscillations are caused by the infant moving around on her mother’s lap, and you can see that the infant is indeed getting more animate as time passes. In ERP studies with infants the aim is therefore to get as many ‘good’ trials (that is, trials during which the infant is looking at the screen and not moving) as possible, but usually many trials have to be excluded. See also A Student’s Guide to Developmental Psychology, Chapter 1, page 15.

This video clip shows a 20-month-old girl picking up two small sweets using a very proficient pincer grasp. You will see that she uses her left hand to pick up the sweets but at this age children do not use a consistent hand for picking up and manipulating objects. On this occasion her left hand was closest to the sweets. Pincers grasps are the most precise of the precision grips and allow humans to carry out very complex manipulation of small objects. See also A Student’s Guide to Developmental Psychology, Chapter 3, page 57.

This video shows a seven-month-old infant in an object permanence task. An interesting object is placed under a cloth in full view of the infant, but the infant does not search for it. See also A Student’s Guide to Developmental Psychology, Chapter 4, page 73.

In the A-not-B task, shown in this video with a 10-month-old, an object is repeatedly hidden in one location (A), and the infant is encouraged to retrieve it. Then, the object is hidden, in full view of the infant, in a new location (B). Nevertheless, the infant continues to search in location A. See also A Student’s Guide to Developmental Psychology Chapter 4, page 73.

This video shows a fast mapping experiment with a 24-month-old toddler. Fast mapping relies on the concept of mutual exclusivity, that children assume that a new word does not refer to an object for which they already know another name. In fast mapping experiments usually three objects are shown on a tray. Two of these objects (and their names) are familiar to the child, and one object is novel. The experimenter then asks for a novel name, e.g. ‘Where is the koba?’ Fast mapping is successful if the child chooses the novel object. In order to ensure that the child does not always just go for the novel object in some trials the experimenter asks for one of the two familiar objects (e.g. ‘Where is the ball?’). The experiment in the video is in three parts. The first part serves to familiarise the child with the task. Here, three familiar objects are shown and the experimenter asks for one of them. The child receives plenty of positive feedback. In the subsequent fast mapping part, objects are presented and asked for as described above. Now, the child is no longer given corrective feedback. The video here contains a third part: after the end of the fast mapping part and a five-minute break, the child’s retention of the novel labels is tested. For this purpose, three of the previously introduced novel objects are shown together and the experimenter asks for one of them. Fast mapping tasks require high concentration by the experimenter: the scene must seem playful and spontaneous but the sequence of objects and questions and the grouping of the objects on the tray are carefully counterbalanced. See also A Student’s Guide to Developmental Psychology, Chapter 5, page 97.

This 16-month-old infant is taking part in a word learning experiment using an eye-tracker. He is sitting on his mother’s lap, looking at a monitor. You can see what happens during one trial of the experiment. The moving red dot indicates where the infant is looking. This trial is composed of two phases: the learning phase and the test phase. During the learning phase the infant sees two novel objects, each associated with novel words. Before each object is presented, a face appears and you can see that the infant looks up to the face. This is to ensure that he is looking in the middle of the monitor screen before the object appears. Once each object has been presented and labelled, both objects are presented on the screen and the infant is asked to look at one of them (target object). If the infant looks significantly longer at the target object than the non-target, this indicates the infant has learned a new word (i.e. the name of the target object). See also A Student’s Guide to Developmental Psychology, Chapter 5, page 98.

In this clip a four-year-old boy is presented with one of the classic Piagetian conservation problems, involving conservation of liquid volume. In the first part of the problem, liquid is poured into two similarly-shaped containers until the boy agrees that they contain the same amount. Then the liquid in one container is poured into another container that is much wider. Watch what happens and listen to the explanation that the boy gives for this judgement about the two quantities. See also A Student’s Guide to Developmental Psychology, Chapter 8, page 135.

This clip involves the same four-year-old boy as in Clip 8. He is presented with another conservation task in which the spacing of two rows of counters is altered to see if this affects his judgement about whether they are the same. He makes the correct judgement in this conservation task, supporting the view that conservation tasks are not of equal difficulty. However, although he makes the correct judgement, the little boy is not able to explain why the two rows of bricks are the same. See also A Student’s Guide to Developmental Psychology, Chapter 8, page 135.

This is a version of one of the most famous theory of mind tasks, the Sally-Ann task. It uses different figures and different objects but the rationale is the same. One character hides an object and then another character moves that object – in this case a hen – to a new location while the first character is away. It is important to establish that the child being tested knows where the hidden object was originally placed and where it is now in order to ensure that this has not been forgotten. The four-year-old boy in the video clip is confidently able to say that the boy doll will expect to find the hen in the original location. He is just at the age when theory of mind understanding is developing. See also A Student’s Guide to Developmental Psychology, Chapter 8, page 148.

The Smarties task is another well-known theory of mind task. It is rather different from the Sally-Ann task because it involves children in making their own judgement about what is in the Smarties tube rather than observing and predicting the behaviour of others. It proves to be more difficult than the Sally-Ann task and the four-year-old boy who succeeded in the Sally-Ann task does not succeed in the Smarties task. See also A Student’s Guide to Developmental Psychology, Chapter 8, page 147.