Monkeys and humans take local uncertainty into account when localizing a change

Abstract

Since sensory measurements are noisy, an observer is rarely certain about the identity of a stimulus. In visual perception tasks, observers generally take their uncertainty about a stimulus into account when doing so helps task performance. Whether the same holds in visual working memory tasks is largely unknown. Ten human and two monkey subjects localized a single change in orientation between a sample display containing three ellipses and a test display containing two ellipses. To manipulate uncertainty, we varied the reliability of orientation information by making each ellipse more or less elongated (two levels); reliability was independent across the stimuli. In both species, a variable-precision encoding model equipped with an “uncertainty–indifferent” decision rule, which uses only the noisy memories, fitted the data poorly. In both species, a much better fit was provided by a model in which the observer also takes the levels of reliability-driven uncertainty associated with the memories into account. In particular, a measured change in a low-reliability stimulus was given lower weight than the same change in a high-reliability stimulus. We did not find strong evidence that observers took reliability-independent variations in uncertainty into account. Our results illustrate the importance of studying the decision stage in comparison tasks and provide further evidence for evolutionary continuity of working memory systems between monkeys and humans.

Variable precision in visual perception

“…Factor importance metrics 6 We consider four model factors: guessing (G), the oblique effect (O), decision noise (D), 7…”

“…Experiment 9, and 6.7 ± 2.7 (AIC) and 0.7 ± 2.7 (BIC) in Experiment 10 (Figure 5B), 6 indicating little or no evidence that factor V is necessary. Consistently, 2⋅LFLP(V) was 7 5.4 ± 3.5 (AIC) and 0.9 ± 4.4 (BIC) in Experiment 9 (Figure 5C), indicating little or no 8 evidence for the presence of factor V. 2⋅LFLP(V) was 8.5 ± 2.9 (AIC) and 6.4 ± 3.3 (BIC) 9…”

“…This is consistent with the model fits to the psychometric curves 32 1/30 to 1/10 -6.8 to -4. 6 Strong evidence for H0 1/100 to 1/10 -9.2 to -6.8 Very strong evidence for H0 <1/100 <-9.2 Extreme evidence for H0…”

“…All blocks were statistically identically to each other. 40 we analyze only the two sessions with "High" heterogeneity (for details, see Mazyar et al 6 (2013)). Each session consisted of four blocks, and each block contained 175 trials, for a 7 total of 1400 trials per subject analyzed here.…”

“…In the Base model, J i is the same across stimuli i and across trials. 6 In the O model, J i is computed from Eq. (2).…”