torekp

Carol puts her left hand in a bucket of hot water, and lets it acclimate for a few minutes. Meanwhile her right hand is acclimating to a bucket of ice water. Then she plunges both hands into a bucket of lukewarm water. The lukewarm water feels very different to her two hands. To the left hand, it feels very chilly. To the right hand, it feels very hot. When asked to tell the temperature of the lukewarm water without looking at the thermocouple readout, she doesn't know. Asked to guess, she's off by a considerable margin. Next Carol flips the thermocouple readout to face her (as shown), and practices. Using different lukewarm water temperatures of 10-35 C, she gets a feel for how hot-adapted and cold-adapted hands respond to the various middling temperatures. Now she makes a guess - starting with a random hand, then moving the other one and revising the guess if necessary - each time before looking at the thermocouple. What will happen? I haven't done the experiment, but human performance on similar perceptual learning tasks suggests that she will get quite good at it. We bring Carol a bucket of 20 C water (without telling) and let her adapt her hands first as usual. "What do you think the temperature is?" we ask. She moves her cold hand first. "Feels like about 20," she says. Hot hand follows. "Yup, feels like 20." "Wait," we ask. "You said feels-like-20 for both hands. Does this mean the bucket no longer feels different to your two different hands, like it did when you started?" "No!" she replies. "Are you crazy? It still feels very different subjectively; I've just learned to see past that to identify the actual temperature." In addition to reports on the external world, we perceive some internal states that typically (but not invariably) can serve as signals about our environment. Let's tentatively call these states Subjectively Identified Aspects of Perception (SIAPs). Even though these states aren't strictly necessary to know what's