Opposing pupil responses to offered and anticipated reward values
- 222 Downloads
Previous studies have shown that the pupils dilate more in anticipation of larger rewards. This finding raises the possibility of a more general association between reward amount and pupil size. We tested this idea by characterizing macaque pupil responses to offered rewards during evaluation and comparison in a binary choice task. To control attention, we made use of a design in which offers occurred in sequence. By looking at pupil responses after choice but before reward, we confirmed the previously observed positive association between pupil size and anticipated reward values. Surprisingly, however, we find that pupil size is negatively correlated with the value of offered gambles before choice, during both evaluation and comparison stages of the task. These results demonstrate a functional distinction between offered and anticipated rewards and present evidence against a narrow version of the simulation hypothesis; the idea that we represent offers by reactivating states associated with anticipating them. They also suggest that pupil size is correlated with relative, not absolute, values of offers, suggestive of an accept–reject model of comparison.
KeywordsMonkey Decision-making Pupil size Value
This work is supported by a CAREER award from NSF (BCS1253576) and a R01 from NIH (DA038615) to BYH. We thank Meghan Castagno, Marc Mancarella and Caleb Strait for assistance with data collection, and the rest of the Hayden lab for valuable discussions.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Statement on the Welfare of Animals
All procedures performed in this study involving animals were in accordance with the ethical standards of the University of Rochester.
- Efron B, Tibshirani RJ (1993) Permutation tests. In: An introduction to the bootstrap. Springer, pp 202–219Google Scholar
- Farovik A, Place RJ, McKenzie S, Porter B, Munro CE, Eichenbaum H (2015) Orbitofrontal cortex encodes memories within value-based schemas and represents contexts that guide memory retrieval. J Neurosci 35:8333–8344. https://doi.org/10.1523/JNEUROSCI.0134-15.2015 CrossRefPubMedPubMedCentralGoogle Scholar
- Lavín C, San Martín R, Jubal ER (2013) Pupil dilation signals uncertainty and surprise in a learning gambling task. Front Behav Neurosci 7Google Scholar
- McNamee D, Liljeholm M, Zika O, O’Doherty JP (2015) Characterizing the associative content of brain structures involved in habitual and goal-directed actions in humans: a multivariate FMRI study. J Neurosci 35:3764–3771. https://doi.org/10.1523/JNEUROSCI.4677-14.2015 CrossRefPubMedPubMedCentralGoogle Scholar
- Preuschoff K, Marius’t Hart B, Einhäuser W (2011) Pupil dilation signals surprise: evidence for noradrenaline’s role in decision making. Front Neurosci 5Google Scholar