FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

Optimally adapting heuristics: humans quickly abandon the constant bearing angle strategy
Collaborators: C.A. Rothkopf 1 , P. Schrater 2
1 Frankfurt Institute for Advanced Studies, 2 University of Minnesota, Minneapolis, USA
Animals ranging from dragonflies through teleost fish to humans all intercept moving targets using the same
strategy of adjusting their speed so as to hold the angle pointing towards their target constant over time. This
constant-bearing-angle strategy has been suggested as a fundamental visuomotor heuristic and as an instance of
Darwininan intelligence that overcomes the need for complex and expensive computations involving multiple
sources of uncertainty.
We consider the task of intercepting a moving ball for which many previous studies have shown that humans
use this constant bearing angle strategy. Here we manipulated the observation function in a virtual reality setup
so as to change the uncertainty of the ball’s position parametrically. Specifically, the contrast of the ball changes
as a function of the heading angle towards the ball along the subject’s momentary trajectory. Subjects adjusted
their interception strategy within an average of 26 trials and were consistently able to catch these balls.
To gain insight into the adopted new interception strategy, we setup two approximate optimal control models,
which know the observation function. In one case, an iterated signal dependent linear- quadratic-Gaussian
controller was modified to handle non-linear observation models. The second approach utilizes a Monte Carlo
sampling of smooth trajectories of increasing complexity in a low dimensional parameter space. These analyses
show that the ideal actor modifies its trajectories by executing controls that increase information gain, and that
these changes mirror human behavior. Thus, we provide evidence that humans quickly abandon the constant
bearing angle strategy in favor of more informative action sequences, if this allows catching moving targets
more reliably. The constant-bearing-angle-strategy is not an invariant heuristic of Darwinian intelligence as
humans employ near-optimal information seeking actions that violate the constant bearing angle strategy, but
produce less uncertainty in the interception.
Left: State space model used to model the interception task. Center: Bearing angle data from human subjects intercepting
a moving ball of constant contrast demonstrating constant bearing angle strategy. Right: Bearing angle data from human
subjects intercepting a moving ball of with variable contrast showing departure from constant bearing angle strategy.
Related publication in 2011:
1) C. A. Rothkopf, P. Schrater, Coupling perception and action using probabilistic control, COSYNE -
Computational and Systems Neuroscience, February 24-27, 2011, Salt Lake City, Utah, USA.
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