Weight Discriminability and Subjective Assessment of Load Heaviness: A Pilot Study

The main objectives of this pilot study were to investigate human ability to: 1) estimate weight of boxes on a lifting task, 2) discriminate among different levels of load, and 3) relate this ability to subjective perception of load heaviness expressed in terms of linguistic descriptors. The effects of color and load differential, defined as a constant weight difference among a series of five boxes, on perception of load heaviness, were also studied. It was shown that the human ability to discriminate among weights of boxes lifted is severely impaired as the load differential decreases below 4 lbs. In addition, as weight of the box exceeds 30 lbs., the difficulty in load differentiation and load estimation, as measured by the number of errors made, significantly increases. This study also suggests that the use of linguistic (verbal) descriptors in the estimation of weights of boxes lifted from the floor to table height, allows for better judgement than the use of numerical values alone.