Biology subjects

Hayden, B. Y.

Publications and source records attributed to Hayden, B. Y..

4 recordsLinked to original sources

bioRxiv2018

Risk aversion in macaques in a freely moving patch-leaving foraging task

Animals, including humans, are risk-averse in most contexts. A major exception is the rhesus macaque (Macaca mulatta), which is robustly risk-seeking. Macaques unique preferences may reflect their unique evolutionary history. Alternatively, they may derive from elements of task design associated with the demands of physiological recording, the source of nearly all macaque risk preference data. To disambiguate these possibilities we assessed macaques risk attitudes in a somewhat more naturalistic environment: subjects foraged at four feeding stations in a large enclosure. Stations (i.e. patches) provided either stochastically or non-stochastically depleting rewards. Subjects patch residence times were longer at safe than at risky stations, indicating a preference for safe options. This preference was not attributable to a win-stay-lose-shift heuristic. These findings highlight the lability of risk attitudes in macaques and support the hypothesis that observed differences between macaques and other species are ephemeral, not evolved.

animal behavior and cognition↗

bioRxiv2018

Exploratory noise governs both flexibility and spontaneous errors and is regulated by cocaine

In many cognitive processes, lapses (spontaneous errors) are attributed to nuisance processes like sensorimotor noise or disengagement. However, some lapses could also be caused by exploratory noise: behavioral randomness that facilitates learning in changing environments. If so, strategic processes would need only up-regulate (rather than generate) exploration to adapt to a changing environment. This view predicts that lapse rates should be correlated with flexibility because they share a common cause. We report that when macaques performed a set-shifting task, lapse rates were negatively correlated with perseverative error frequency. Furthermore, chronic exposure to cocaine, which impairs cognitive flexibility, increased perseverative errors, but, surprisingly, improved overall performance by reducing lapse rates. We reconcile these results with a model in which cocaine decreased exploration by deepening attractor basins corresponding to rules. These results support the idea that exploratory noise contributes to lapses, meaning that it affects rule-based decision-making even when it has no strategic value.

neuroscience↗

bioRxiv2018

Opposing pupil responses to offered and anticipated reward values

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.

neuroscience↗

bioRxiv2018

Monkeys predict trajectories of virtual prey using basic variables from Newtonian physics.

The demands of foraging are a major driver in the evolution of cognitive faculties. To successfully pursue a mobile prey that is attempting to avoid capture, the ability to predict its flight path can provide a crucial advantage. We hypothesized that, during pursuit, rhesus macaques exploit patterns in preys behavior to predict the preys future positions. We modeled behavior of three macaques in a joystick-controlled pursuit task in which prey follow simple escape algorithms that involve repulsion from the subject and from the walls of the virtual enclosure. We find that, even in this artificial task, macaques actively predict and aim towards preys future positions, increasing their foraging success. Their predictions are derived from the three core variables in Newtonian dynamics: position, velocity, and acceleration. Even after extensive training, subjects favored these principles and ignored other regularities in prey behavior. Most notably, they ignored the effects their own actions would have on the prey, despite extensive training and even though doing so would have further improved performance. We conjecture that subjects have a strong bias towards using physical principles to pursue fleeing prey, possibly reflecting an evolved physics module. The observed predictive behavior suggests that foraging demands facilitate the development of prospection.

animal behavior and cognition↗