A current trend in human computer Interaction research is to use physiological measurements to gather data while users are engaged in the software or website which is being tested.

A big problem, however, is that the users do not tend to feel at ease when they are connected to these complex hardware systems. This may hamper the elicitation of natural behaviour. Therefore non obtrusive measuring tools need to be created.

This instructable is a first attempt in that direction. A Standard old Dell computer mouse was outfitted with GRS electrodes. This way physiological data can be gathered withour hampering the user.

Step 1: Preparation

What you need:

- A computer mouse
- a drill
- 2 AA batteries
- tape
- Thin electric wire
- Connectors

Step 2: Preparing the Mouse - 1

This step basically shows you how to dismantle the mouse. We need to remove the buttons to fit the electrodes.

Mouse types may varty, but the two I worked on were rather similar.

Step 3: Preparing the Mouse - 2

The pictures will show you where the holes need to be drilled.

the middle of each button should be the place to drill to add the electrodes.
Basically choose the place which seems natural to you. the electrodes should connect to the tops of the fingers (where ones finger prints are).

Another 2 holes need to be drilled in the mouse structure itself in order to pass the wires

Step 4: Placing the Electrodes

I used the + pole of a standard AA type battery as this is the ideal shape and size for the job.
Do not use Duracell batteries as they weld the poles to the core.

Carefully remove the casing of the battery without harming the core.

Remove the positive and negative poles of the battery. these are usually glued to the chemical core, you shouldn't harm the chemical centre of the battery during this step.

The following steps are clearer by following the pictures. the show how to attach the wires and fix the electrodes in the right place.

Step 5: Finishing and Testing

Reassemble you mouse.

Attach it to you bio measuring device and test it.

To give the mouse a finished look you could use electric tape to tape the wires together.

don't be afraid that users might lift their fingers off the electrodes. A disconnection gives a very clear signal which can be easily filtered out.

The device you use to acquire the data may differ off course. Our lab uses the MP100 system by Biopac. Its an extensible lab giving you the options to add multiple measuring devices. To date we only have the GSR unit and a ECG unit. The advantage with this unit is that is has the ability to synchronise with the Noldus Observer software. This package is used by many usability and behavioural labs to gather observational data.