The speaker describes a scenario where a baboon in the African savanna faces a survival dilemma of choosing whether to risk its life for bananas near a lion. The decision involves calculating probabilities: the likelihood of starving if it doesn't eat versus the likelihood of being attacked by the lion. The baboon, like humans, collects data about the bananas (quantity, ripeness) and the lion (distance, size, state) and uses its senses to process this information. The entire body, especially the nervous system and brain, acts as a calculator, swiftly translating the data into probabilities. Instead of numerical results, the baboon experiences the answer as a feeling or emotion.