‘Where’s my hand?’
An almost automatic reaction to being unexpectedly touched is to look towards the part of our body where the touch occurred. This is because we know where this part of our body is in visual space and we turn our heads to bring possible causes of the touch stimulus into view. Previous research found that this ability develops between 6 and 10 months of age.
In this study, we want to know how the brain responds to an unexpected touch sensation. We therefore present short vibrations to the palms of the infant hands and record their brain activity.
Also, in one part of the experiment we are doing something to make the task a little harder for the infants: crossing their hands. In touch sense localisation tasks, crossing the hands makes localisation a little more difficult and slower; it seems to confuse us when our hands are not on the side of the body where they rest usually.
The ‘Rubber Hand’
How do I know where my hand is?
I might know where my hand is by looking at it; or because, through my muscles, I can feel its position relative to the rest of my body. A child has less experience than an adult in sensing where her hand is, and so this study tests whether children rely more on vision than adults to judge the position of the hand.
To do this we use the ‘Rubber Hand Illusion’, which has been used with adults. In this situation the participant can feel where their hand is, but can see a ‘fake’ hand (a rubber glove) in a different position. We then ask people to make pointing movements, and measure on graph paper where they point to. Since vision and muscle information signal different things about where the hand is, in this situation adults tend to move their hand differently to normal.
‘Tickling Fingers’
The study aims to investigate how children learn to reach across their midlines to pick up objects and how this helps them to learn to locate their hands in space without visual cues or information. During the course of the study, children simply have to carry out three reaching tasks e.g. picking up beans and placing them in a jaw with a pair of large tweezers, threading doughnut shaped toys through vertical rods and rolling marbles across horizontal tracks. Following this, we will administer a gentle tactile stimulus to their fingers, which feels like a light tickling sensation, to see if they are able to discriminate between which hand was stimulated and where that hand was located in peri-personal space.
‘Hand or Arm?’
The study involves judging how far apart two stimuli on the hand and/or arm are. It has been shown in adults (de Vignemont et al, 2008) that touches which are presented across two different body parts (hand and arm) are judged to be further apart than two equally distanced touches on the same body part (e.g. both on the arm). This is due to the way we segment our body into categories in our mind; hand and arm are separate entities and therefore deemed to be further apart. Previous developmental research has focused on how infants interact with the environment, less is known about how they learn about their body as the vehicle for this interaction. By selecting 3 age groups known to have different abilities (3, 6 and 9 years of age), I aim to investigate when and how young children begin to appreciate the distinction between their body parts.