Figure 9. Turning biases favor exploration.

(A) Definition of four turning biases at a T-junction based on the ratios of actions taken. Top: An animal arriving from the stem of the T (shaded) may either reverse or turn left or right. $P_{\mathrm{SF}}$ is the probability that it will move forward rather than reversing. Given that it moves forward, $P_{\mathrm{SA}}$ is the probability that it will take an alternating turn from the preceding one (gray), that is left-right or right-left. Bottom: An animal arriving from the bar of the T may either reverse or go straight, or turn into the stem of the T. $P_{\mathrm{BF}}$ is the probability that it will move forward through the junction rather than reversing. Given that it moves forward, $P_{\mathrm{BS}}$ is the probability that it turns into the stem. (B) Scatter graph of the biases $P_{\mathrm{SF}}$ and $P_{\mathrm{BF}}$ (left) and $P_{\mathrm{SA}}$ and $P_{\mathrm{BS}}$ (right). Every dot represents a mouse. Cross: values for an unbiased random walk. (C) Exploration curve of new end nodes discovered vs end nodes visited, displayed as in Figure 8A, including results from a biased random walk with the four turning biases derived from the same mouse, as well as a more elaborate Markov-chain model (see Figure 11C). (D) Efficiency of exploration (Equation 1) in 19 mice compared to the efficiency of the corresponding biased random walk.