The Book of Days (1864) by the Scottish author Robert Chambers reports a curious legal case: in 1457 in the town of Lavegny, a sow and her piglets were charged and tried for the murder of a partially eaten small child. After much deliberation, the court condemned the sow to death for her part in the act, but acquitted the naive piglets who were too young to appreciate the gravity of their crimes.
Subjecting a pig to a criminal trial seems perverse through modern eyes, since many of us believe that humans possess an awareness of actions and outcomes that separates us from other animals. While a grazing pig might not know what it is chewing, human beings are surely abreast of their actions and alert to their unfolding consequences. However, while our identities and our societies are built on this assumption of insight, psychology and neuroscience are beginning to reveal how difficult it is for our brains to monitor even our simplest interactions with the physical and social world. In the face of these obstacles, our brains rely on predictive mechanisms that align our experience with our expectations. While such alignments are often useful, they can cause our experiences to depart from objective reality – reducing the clear-cut insight that supposedly separates us from the Lavegny pigs.
One challenge that our brains face in monitoring our actions is the inherently ambiguous information they receive. We experience the world outside our heads through the veil of our sensory systems: the peripheral organs and nervous tissues that pick up and process different physical signals, such as light that hits the eyes or pressure on the skin. Though these circuits are remarkably complex, the sensory wetware of our brain possesses the weaknesses common to many biological systems: the wiring is not perfect, transmission is leaky, and the system is plagued by noise – much like how the crackle of a poorly tuned radio masks the real transmission.
But noise is not the only obstacle. Even if these circuits transmitted with perfect fidelity, our perceptual experience would still be incomplete. This is because the veil of our sensory apparatus picks up only the ‘shadows’ of objects in the outside world. To illustrate this, think about how our visual system works. When we look out on the world around us, we sample spatial patterns of light that bounce off different objects and land on the flat surface of the eye. This two-dimensional map of the world is preserved throughout the earliest parts of the visual brain, and forms the basis of what we see. But while this process is impressive, it leaves observers with the challenge of reconstructing the real three-dimensional world from the two-dimensional shadow that has been cast on its sensory surface. [Continue reading…]