The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

Francesca came into the lab one day, having seen an ad in the San Diego Reader. After tea and the usual pleasantries my student David Brang and I hooked her up to our ohmmeter to measure her GSR. As we saw in the Chapter 2, this device measures the moment-to-moment microsweating produced by fluctuating levels of emotional arousal. Unlike a person, who can verbally dissemble or even be subconsciously deluded about how something makes her feel, GSR is instantaneous and automatic. When we measured GSR in normal subjects who touched various mundane textures such as corduroy or linoleum, it was clear they experienced no emotions. But Francesca was different. For the textures that she reported gave her strong emotional reactions, such as fear or anxiety or disgust, her body produced a strong GSR signal. But when she touched textures that she said gave her warm, relaxed feelings, there was no change in the electrical resistance of her skin. Since you cannot fake GSR responses, this provided strong evidence that Francesca was telling us the truth.

But to be absolutely sure that Francesca was experiencing specific emotions, we used an added procedure. Again we took her into a room and hooked her up to the ohmmeter. We asked her to follow instructions on a computer screen that would tell her which of several objects that were laid out on the table in front of her she was to touch and for how long. We said she would be alone in the room since noises from our presence might interfere with the GSR monitoring. Unbeknownst to her, we had a hidden video camera behind the monitor to record all her facial expressions. The reason we did this secretively was to ensure that her expressions were genuine and spontaneous. After the experiment, we had independent student evaluators rate the magnitude and quality of the expressions on her face, such as fear or calm. Of course we made sure that the evaluators didn’t know the purpose of the experiment and didn’t know what object Francesca had been touching on any given trial. Once again we found that there was clear correlation between Francesca’s subjective ratings of various textures and her spontaneous facial expressions. It seemed quite clear, therefore, that the emotions she claimed to experience were authentic.

MIRABELLE, AN EBULLIENT, dark-haired young lady, had been eavesdropping on a conversation I had been having with Ed Hubbard at the Espresso Roma Cafe on campus, a stone’s throw away from my office. She arched her eyebrows—whether from amusement or skepticism, I couldn’t tell.

She came to our lab shortly thereafter to volunteer as a subject. Like Susan and Becky, every number appeared to Mirabelle to be tinged with a particular color. Susan and Becky had convinced us informally that they were reporting their experience accurately and truthfully, but with Mirabelle we wanted to see if we could scare up some hard proof that she was really seeing color (as when you see an apple) rather than just experiencing a vague mental picture of color (as when you imagine an apple). This boundary between seeing and imagining has always proved elusive in neurology. Perhaps synesthesia would help resolve the distinction between them.

I waved her toward a chair in my office, but she was reluctant to sit. Her eyes darted all around the room looking at the various antique scientific instruments and fossils lying on the table and on the floor. She was like the proverbial kid in a candy store as she crawled all around the floor looking at a collection of fossil fishes from Brazil. Her jeans were sliding down her hips, and I tried not to gaze directly at the tattoo on her waist. Mirabelle’s eyes lit up when she saw a long, polished fossilized bone which looked a bit like a humerus (upper arm bone). I asked her to guess what it was. She tried rib, shin bone, and thigh bone. In fact, it was the baculum (penis bone) of an extinct Pleistocene walrus. This particular one had obviously been fractured in the middle and had rehealed at an angle while the animal was alive, as evidenced by a callus formation. There was also a healed, callused tooth mark on the fracture line, suggesting the fracture had been caused by a sexual or predatory bite. There is a detective aspect to paleontology just as there is in neurology, and we could have gone on with all this for another two hours. But we were running out of time. We needed to get back to her synesthesia.