IN experiments on the perception of elasticity, we have found that individuals equate a pull on an expanding elastic spring with a much lighter lifted weight impression. Lifting a weight of 2.50 kilograms (for which the psycho-physical limen is of the order 0.10 kilogram) was matched by one person with a pull as large as 6.50 kilograms (probable error 0.20 kilogram). On the average, from results with some fifty persons, a lift of 2.50 kilograms is matched for weight with a pull on a spring of 4.00 kilograms approximately (probable error 0.25 kilogram). The under-estimation of the spring or elastic pull in terms of weight perception is of the same order irrespective of whether the subject begins with a zero pull in the spring, gradually increasing this until a match with the lifted weight impression is obtained, or whether he begins with a pull of the order 8.00 kilograms, gradually decreasing this until a match is obtained. The effects are just as marked, also, when a pull is used as standard for comparison with a series of lifted weights.