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Jacky Pett
Hampshire, UK
If you have used your right hand to test the temperature of the bathwater all your life, then it has been trained to know what the “right” temperature is to within a fine tolerance, whereas your left hand only knows roughly within a broad tolerance.
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I am a right-hander and use my right hand to test the bathwater. However, I find that the temperature that is right for this hand is often wrong for the rest of me. My right hand is less sensitive to hot or cold on the skin than my left hand, wrists or elbows, which are all better places for testing bathwater.
This means that water I can put my right hand into may be uncomfortably hot or cold for other parts of my body. I suspect this is related to the ability of many cooks to easily hold dishes that others find too hot.
This hypothesis is complicated by me being left-handed for some things and not others, partly due to being told to write with my right hand at school. So my right-handedness may not be a valid comparison.
Selina Dussaye
Via email
Repeated use of a dominant hand for tasks like checking the bathwater may mean that there are more neural pathways in the brain dedicated to analysing information received through the sensory receptors in that hand.
Daniel Casasanto
Department of Psychology, Cornell University, Ithaca, New York, US
This is the first time I have heard of someone being able to discriminate temperature better with their right hand than with their left.
Whether this pattern is found in people more generally is an open question.
If so, here is a possible reason why it could happen. People use their dominant and non-dominant hands differently. The dominant hand is used for more “approach-related” actions, in which you engage with the world around you in an intentional way.
The non-dominant hand more often performs “avoidance-related” actions, in which you are responding reflexively to prevent something bad from happening. I call this the sword and shield pattern of hand use.
The person asking this question is reporting less temperature sensitivity in their non-dominant “shield hand”. It would make sense, evolutionarily, for the shield hand to have reduced sensitivity given that it is more likely to be injured in the service of classic avoidance actions, such as fending off attack.
This is just a hypothesis. An easy way to test it would be to find out whether, on average, right-handed people have less sensitivity to temperature (and presumably also to pain) in their shielding left hand, whereas left-handed individuals have less sensitivity in their right hand.
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