Hypothetical and real choice differentially activate common valuation areas

Abstract

Hypothetical reports of intended behavior are commonly used to draw conclusions about real choices. A fundamental question in decision neuroscience is whether the same type of valuation and choice computations are performed in hypothetical and real decisions. We investigated this question using functional magnetic resonance imaging while human subjects made real and hypothetical choices about purchases of consumer goods. We found that activity in common areas of the orbitofrontal cortex and the ventral striatum correlated with behavioral measures of the stimulus value of the goods in both types of decision. Furthermore, we found that activity in these regions was stronger in response to the stimulus value signals in the real choice condition. The findings suggest that the difference between real and hypothetical choice is primarily attributable to variations in the value computations of the medial orbitofrontal cortex and the ventral striatum, and not attributable to the use of different valuation systems, or to the computation of stronger stimulus value signals in the hypothetical condition.

Figure 1.

Experimental procedure. A, Timeline of the entire experiment. B, An example screen for the prescanning trials. C, Time structure of an individual trial in the scanning part. The structure of the hypothetical and real trials was identical. There was no repetition of a product between the hypothetical and real trials and subjects were asked to specify their decision (“yes” or “no”) as well as the confidence level (“strong” or “weak”) in the decision. During the product image presentation, subjects were asked to press any button as soon as they had reached a decision. The response time during this phase were used for fMRI analysis. Subjects were given up to 4 s to submit their decision. Buttons assigned to each decision response were counterbalanced across blocks and subjects. Failure to submit a decision was treated as a missed response.

Figure 2.

Behavioral results: choices show a hypothetical “yes” bias. A, Choice data averaged across all 24 subjects. Subjects made more “yes” purchase decisions in hypothetical trials (mean frequency ± SEM). SN, Strong no; WN, weak no; WY, weak yes; SY, strong yes. n.s., Not significant. *p < 0.005. B, Correction of biases in DV. The curves show fitted probability of “yes” purchase decisions before correction (top) and after correction (bottom). C, Median estimated θ for hypothetical and real trials. Signed-rank test, **p < 0.0003. Error bars indicate SEs. D, Average decision time in hypothetical and real trials by sign of mDV. Paired two-sample t test, ***p < 0.008. Error bars indicate SEs.

Figure 3.

Neural activity modulated by mDV and DV in real versus hypothetical decisions. A, C, The brain encodes mDV and DV in the same areas in real and hypothetical trials. Overlay of contrasts real*mDV and hypothetical*mDV contrasts (A) and real*DV and hypothetical*DV contrasts (C). The “real” areas are a superset of the “hypothetical” areas. p < 0.001, uncorrected. B, D, Conjunction analysis of real*mDV and hypothetical*mDV contrasts (B) and real*DV and hypothetical*DV contrasts (D) was performed to test the conjunction null hypothesis at a threshold p < 0.001, uncorrected. The mOFC and VStr show conjointly significant activations modulated by mDV and DV in both real and hypothetical decision making.

Figure 4.

Value signals stronger in the valuation systems during real choice. A, The mOFC is more actively engaged when real decisions are being made, compared with hypothetical decisions (contrast without decision value modulator: real vs hypothetical; k ≥ 5 voxels; orange: p < 0.001, uncorrected; red: p < 0.005, uncorrected). B, Significantly active areas in the (real*mDV − hypothetical*mDV) contrast. The mDV modulates mOFC and VStr activations in hypothetical decision making to a lesser extent. k ≥ 5 voxels; orange: p < 0.001, uncorrected; red: p < 0.005, uncorrected. C, Subjects exhibited higher responsivity to mDV in real trials compared with hypothetical trials (mean β ± SEM).

Figure 5.

Differential modulation of DV in real versus hypothetical decisions. A, Regions showing differential sensitivity to DV in real trials compared with hypothetical trials. (real*DV − hypothetical*DV) contrast. Orange: p < 0.001; red: p < 0.005, uncorrected; k ≥ 5. B, Average β values from hypothetical*DV and real*DV contrasts, respectively, within the mOFC regions activated in both contrasts. As in Figure 4C, to avoid overfitting, the mOFC ROIs for each subject were defined based on the second-level real*DV and hypothetical*DV contrasts, which were independently generated using data from the rest of the N − 1 subjects. Paired two-sample t test.