IMAGINE what it must be like. In a condition called synesthesia, senses blend, with exotic effects. Each number may evoke its own color, and flavors can mingle with shapes—in one instance letting a man tell that a roasted chicken was done, because it tasted “pointy.” In their article, “Hearing Colors, Tasting Shapes,” starting on page 76, Vilayanur S. Ramachandran and Edward M. Hubbard describe how synesthesia has yielded insights into how the brain processes complex sensory inputs.

We take our conventional set of senses for granted, but their capabilities are no less astounding for their everyday qualities. The constant stream of data they provide helps the brain interpret our surroundings, giving us vital tools to survive and thrive. As Nobel Prize winner Richard Axel writes in “The Molecular Logic of Smell,” beginning on page 68, humans “can recognize approximately 10,000 scents, ranging from the pleasurable scent of freshly cut flowers to the aversive smell of an angry skunk.” Other senses leap into action to protect us from such foul-smelling danger. Interpreting acoustic signals from our two ears, the brain locates the rustling of an animal on the forest floor. At the same time, our visual systems near-instantly assemble into a coherent whole the scattered patches of black and white peeking through the leaves: “Skunk!”

When bereft of sensory feedback, the brain hastens to compensate, with revealing results. “Phantom Limbs,” by Ronald Melzack, on page 52, describes the enduring mental presence of missing appendages, whereas “How the Blind Draw,” by John M. Kennedy, on page 44, discusses a surprising connection between vision and touch.

As scientists try to make sense of our senses, they also seek to imitate or even improve on them to serve us in new ways. “Neuromorphic Microchips,” by Kwabena Boahen, starting on page 20, describes work to etch visual systems in silicon for better artificial-recognition technologies. Kathryn S. Brown's story, which asks “Are You Ready for a New Sensation?”, explores how biology is combining with engineering to design the sensory experiences of tomorrow; turn to page 60. These thought-provoking pieces, and the others in the issue, offer what we hope will be a sensational experience.

Executive Editor Scientific American