Independent Neural Computation of Value from Other People's Confidence

Abstract

Expectation of reward can be shaped by the observation of actions and expressions of other people in one's environment. A person's apparent confidence in the likely reward of an action, for instance, makes qualities of their evidence, not observed directly, socially accessible. This strategy is computationally distinguished from associative learning methods that rely on direct observation, by its use of inference from indirect evidence. In twenty-three healthy human subjects, we isolated effects of first-hand experience, other people's choices, and the mediating effect of their confidence, on decision-making and neural correlates of value within ventromedial prefrontal cortex (vmPFC). Value derived from first-hand experience and other people's choices (regardless of confidence) were indiscriminately represented across vmPFC. However, value computed from agent choices weighted by their associated confidence was represented with specificity for ventromedial area 10. This pattern corresponds to shifts of connectivity and overlapping cognitive processes along a posterior-anterior vmPFC axis. Task behavior and self-reported self-reliance for decision-making in other social contexts correlated. The tendency to conform in other social contexts corresponded to increased activation in cortical regions previously shown to respond to social conflict in proportion to subsequent conformity (Campbell-Meiklejohn et al., 2010). The tendency to self-monitor predicted a selectively enhanced response to accordance with others in the right temporoparietal junction (rTPJ). The findings anatomically decompose vmPFC value representations according to computational requirements and provide biological insight into the social transmission of preference and reassurance gained from the confidence of others.

Significance statement: Decades of research have provided evidence that the ventromedial prefrontal cortex (vmPFC) signals the satisfaction we expect from imminent actions. However, we have a surprisingly modest understanding of the organization of value across this substantial and varied region. This study finds that using cues of the reliability of other peoples' knowledge to enhance expectation of personal success generates value correlates that are anatomically distinct from those concurrently computed from direct, personal experience. This suggests that representation of decision values in vmPFC is suborganized according to the underlying computation, consistent with what we know about the anatomical heterogeneity of the region. These results also provide insight into the observational learning process by which someone else's confidence can sway and reassure our choices.

Keywords: confidence; decision; observational learning; social; value; ventromedial prefrontal cortex.

Figure 1.

Urn task. On each trial, a new urn of randomly mixed marbles is presented. Contents are hidden. Animation of five hands individually reaching for five different samples from the urn occurs (the first two parts last 1.5 to 2 s). Predictions of the next marble drawn from the urn and their associated confidence in those predictions of four agents are shown. Agents were represented as sepia-toned faces with neutral expression. Agents' predictions were expressed by the color of the circle positioned next to their faces. Confidence indicated as the expression within that circle and the speed at which the answer was shown (rapid + smug = high confidence). Agents' answers took between 300 and 2500 ms to appear. Once agents' choices were in, they remained on the screen for 1250 s. Next, the participant's own sample of marbles appeared from the bottom of the screen was displayed with all other information for a further 1250 ms. The sample contained eight marbles, with one to seven of them being red. This was the event modeled in the fMRI analysis. Finally, the participant was asked to make a prediction (red or green). No choice feedback was provided.

Figure 2.

Behavioral effects. Probability (mean proportion) of choices for red as a function of: reds in sample (A), frequency and confidence of red choices by agents (B), and frequency and confidence of green choices by agents (C). Error bars indicate SE.

Figure 3.

Neural representation of value in vmPFC. Activations color-coded with respect to amount of evidence supporting the likelihood of the participant's choice being correct (clusters defined by Z > 3.0, cluster significance p < 0.05). A, Neural representation of value from the integrated value fMRI model combining all available information. B, Distribution and overlap of activity correlating with increasing and decreasing value computed from information sources of the component value fMRI model. S_A = personal sample, O_A = agent choices, O_AC_A = interaction of agent choices and their confidence.

Figure 4.

Effect time courses across vmPFC. A, Anatomically defined spherical regions of interest spanning the superior medial gyrus from area 14 m (Mackey and Petrides, 2010) to ventromedial area 10. B, Plots of mean effects of interest within the component value fMRI model across 5 time bins are 2.8 s (1 TR) beginning at the onset of agents' responses. Figure shows relative nonspecificity of S_A and O_A across the region, the increasing specificity of O_AC_A toward dorsoanterior regions, and the sustained response to agents' choices O_A into the response window of S_A. Error bars indicate SE.

Figure 5.

Effects of confident and unconfident agents across vmPFC. Mean effect of an adapted component value fMRI model that separates effects of confident agents' choices from unconfident agents' choices across the five spheres and time bins of Figure 4 are shown. Figure shows the increasing specificity of socially learned value that is contingent on agents' confidence toward dorsoanterior regions of vmPFC. Error bars indicate SE.

Figure 6.

Individual differences of task behavior. Effects of information sources on choices, for each individual, were added as covariates to the component value fMRI model analysis. vmPFC responses to S_A are predicted by the influence of samples on choice behavior. amPFC responses to O_A are predicted by the relative influence of agents (O effect − S effect) on choice behavior.

Figure 7.

Social influence in other situations. A, Scatterplot showing relationship between the use of one's own sample during the urn task (arbitrary units) and self-reported reliance on agents outside of the laboratory. B, Between subjects, those more likely to conform in other social situations respond more to conflict with agents and less conflict with personal samples within regions shown previously to predict conformity from social conflict responses (Campbell-Meiklejohn et al., 2010). C, Between subjects, rTPJ responds more to accordance of agents' choices in proportion to tendency to adapt behavior to social cues in real-world situations (self-monitoring).