Numbing or sensitization? Replications and extensions of Fetherstonhaugh et al. (1997)'s “Insensitivity to the Value of Human Life”

Abstract Is it better to save 4500 lives out of 11,000 or 4500 lives out of 250,000? Fetherstonhaugh et al. (1997) showed that people prefer the former: to save lives if they are a higher proportion of the total, a phenomenon they termed “psychophysical numbing”. We attempted to replicate Studies 1 and 2 of Fetherstonhaugh et al. (1997) (5 data collections, total N = 4799, MTurk and Prolific, USA and UK), and added several extensions (e.g., donation amounts, procedural differences, and individual-level ideology and knowledge). We found mixed support, with two successful replications of Study 2 that indeed showed psychophysical numbing (original: η2p = 0.55, 90% CI [0.45, 0.62], Study 2a: η2p = 0.62, 90% CI [0.58, 0.66], Study 2b: η2p = 0.24, 90% CI [0.21, 0.27], all in same direction), yet also three unsuccessful replications of Study 1 showing instead an opposite psychophysical sensitization, a preference for saving a smaller proportion of lives (original effect size: η2p = 0.14, 90% CI [0.02, 0.28], replications: Study 1a: η2p = 0.06, 90% CI [0.02, 0.10], Study 1b: η2p = 0.21, 90% CI [0.17, 0.26]; Study 1c: η2p = 0.13, 90% CI [0.08, 0.17], all in the opposite direction). We discuss theoretical implications and potential drivers of psychophysical numbing and sensitization, including evaluation mode, comparison procedure, ideology, knowledge, and prioritizing of one's own country, and practical implications for research on perceptions of charity, aid effectiveness, and donations. Materials, preregistrations, data, and analyses are available at https://osf.io/786jg/ .