(A) Schematic illustration of the residual and intact limbs. (B) Limb-use strategies, based on activity monitors for increased lateralised (intact hand) use. A laterality index, reflecting the relative number of movements performed by the intact hand vs the residual limb, was calculated using data from acceleration monitors (mean ± s.e.m.), worn by 20 1-handed individuals (8 congenital) while engaged in their normal routines. Positive values represent a tendency to use the intact hand more than the residual limb. Although both groups exhibit such a tendency (t(7) = 3.48, p=0.01; t(11) = 10.60, p=0.001, one-sample t-test compared to zero for the congenital and acquired groups, respectively), the acquired group shows a significantly greater preference for the intact hand compared to the congenital group (t(18) = −2.67, p=0.016). (C) Questionnaire ratings (mean ± s.e.m.) for residual arm usage in daily activities were significantly greater for the congenital group (t(1,27) = 3.65, p=0.001), suggesting they use their residual arm more frequently in daily activities, compared with the acquired group. (D) Questionnaire ratings for residual arm usage were negatively correlated with the laterality indices, measured based on acceleration monitoring (r(20) = −0.53, p=0.012), validating the questionnaires as a measurement of habitual usage strategies between the residual and intact limbs. Scatter plot shows data for 1-handed individuals with congenital and acquired hand loss, frequency of prosthetic hand usage is indicated in the index to the right. Asterisks denote significance levels of *p<0.05; ***p<0.005.