Carsten Höller trained as a scientist before he became a visual artist, and his core interest was behavioural science. An equal number of canaries or two different species are held in two equally sized cages that are linked to each other by a scale, hanging from the ceiling. Both aviaries are also similar in design, weight and features. The needle and dial at the main suspension enables the visitor to read whether the two elements hang at the same level, or if the movements of the birds have altered the equilibrium. One is drawn to observe the differences between the behaviour of the birds in each cage: their song, their flight pattern, etc.