PT  - JOURNAL ARTICLE
AU  - Brian Maniscalco
AU  - Brian Odegaard
AU  - Piercesare Grimaldi
AU  - Seong Hah Cho
AU  - Michele A. Basso
AU  - Hakwan Lau
AU  - Megan A. K. Peters
TI  - Tuned normalization in perceptual decision-making circuits can explain seemingly suboptimal confidence behavior
AID  - 10.1101/558858
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 558858
4099  - http://biorxiv.org/content/early/2019/03/20/558858.short
4100  - http://biorxiv.org/content/early/2019/03/20/558858.full
AB  - Current dominant views hold that perceptual confidence reflects the probability that a decision is correct. Although these views have enjoyed some empirical support, recent behavioral results indicate that confidence and the probability of being correct can be dissociated. An alternative hypothesis suggests that confidence instead reflects the magnitude of evidence in favor of a decision while being relatively insensitive to the evidence opposing the decision. We considered how this alternative hypothesis might be biologically instantiated by developing a simple leaky competing accumulator neural network model incorporating a known property of sensory neurons: tuned normalization. The key idea of the model is that each accumulator neuron’s normalization ‘tuning’ dictates its contribution to perceptual decisions versus confidence judgments. We demonstrate that this biologically plausible model can account for several counterintuitive findings reported in the literature, where confidence and decision accuracy were shown to dissociate -- and that the differential contribution a neuron makes to decisions versus confidence judgments based on its normalization tuning is vital to capturing some of these effects. One critical prediction of the model is that systematic variability in normalization tuning exists not only in sensory cortices but also in the decision-making circuitry. We tested and validated this prediction in macaque superior colliculus (SC; a region implicated in decision-making). The confirmation of this novel prediction provides direct support for our model. These findings suggest that the brain has developed and implements this alternative, heuristic theory of perceptual confidence computation by capitalizing on the diversity of neural resources available.Significance The dominant view of perceptual confidence proposes that confidence optimally reflects the probability that a decision is correct. But recent empirical evidence suggests that perceptual confidence exhibits a suboptimal ‘confirmation bias’, just as in human decision-making in general. We tested how this ‘bias’ might be neurally implemented by building a biologically plausible neural network model, and showed that the ‘bias’ emerges when each neuron’s degree of divisive normalization dictates how it drives decisions versus confidence judgments. We confirmed the model’s biological substrate using electrophysiological recordings in monkeys. These results challenge the dominant model, suggesting that the brain instead capitalizes on the diversity of available machinery (i.e., neuronal resources) to implement heuristic -- not optimal -- strategies to compute subjective confidence.