Supplementary Figure 1: Reward rate affects the decision to begin work.

(a) Latency distributions are bimodal, and depend on reward rate. Very short latencies (early peak) preferentially occur when a greater proportion of recent trials have been rewarded (same data set as Fig 1d–i). (b) (top) Schematic of video analysis. Each trial was categorized as “engaged” (already waiting for Light-On) or non-engaged based upon distance (s) and orientation (θ) immediately before Light-On (see Methods). (bottom) Arrows indicate rat head position and orientation for engaged (pink) and non-engaged (green) trials (one example session shown). (c) Categorization into engaged, non-engaged trials accounts for bimodal latency distribution (data shown are all non-laser trials across 12 ChR2 sessions in TH-Cre⁺ rats). (d) Proportion of engaged trials increases when more recent trials have been rewarded (3336 trials from 4 rats, r=0.82, p=0.003). (e) Especially for non-engaged trials, latencies are lower when reward rate is higher (r=−0.11,p=0.004 for 1570 engaged trials, r=−0.18, p=5.2×10⁻¹⁹ for 1766 non-engaged trials).