Cross-dimensional magnitude interactions arise from memory interference

Magnitudes from different dimensions (e.g., space and time) interact with each other in perception, but how these interactions occur remains unclear. In four experiments, we investigated whether cross-dimensional magnitude interactions arise from memory interference. In Experiment 1, participants perceived a constant-length line consisting of two line segments of complementary lengths and presented for a variable stimulus duration; then they received a cue about which of the two segment lengths to later reproduce. Participants were to first reproduce the stimulus duration and then the cued length. Reproduced durations increased as a function of the cued length if the cue was given before duration was retrieved from memory for reproduction (i.e. before duration reproduction; Experiment 1) but not if it was given after the duration memory had been retrieved from memory (i.e. after the start of duration reproduction; Experiment 2). These findings demonstrate that space-time interaction arises as a result of memory interference when length and duration information co-exist in working memory. Experiment 3 further demonstrated spatial interference on duration memories from memories of filled lengths (i.e. solid line segments) but not from noisier memories of unfilled lengths (demarcated empty spatial intervals), thus highlighting the role of memory noise in space-time interaction. Finally, Experiment 4 showed that time also exerted memory interference on space when space was presented as (relatively noisy) unfilled lengths. Taken together, these findings suggest that cross-dimensional magnitude interactions arise as a result of memory interference and the extent and direction of the interaction depend on the relative memory noises of the target and interfering dimensions. We propose a Bayesian model whereby the estimation of a magnitude is based on the integration of the noisily encoded percept of the target magnitude and the prior knowledge that magnitudes co-vary across dimensions (e.g., space and time). We discuss implications for cross-dimensional magnitude interactions in general.