Toothed whale porpoise as a fish. Toothed whales, as well as baleen whales, are descendants of land-dwelling mammals of the artiodactyl order (even-toed ungulates). They are closely related to the hippopotamus, sharing a common ancestor that lived around 54 million years ago (mya). The primitive cetaceans, or archaeocetes, first took to the sea approximately 49 mya and became fully aquatic by 5–10 million years later. The adaptation of echolocation and enhanced fat synthesis in blubber occurred when toothed whales split apart from baleen whales, and distinguishes modern toothed whales from fully aquatic archaeocetes. This happened around 34 mya. Unlike toothed whales, baleen
Divided visual field paradigm a lateralized stimulus can be as fast as 150ms following stimulus onset, the lateralized stimulus should only be presented for a duration of 180ms at most. A free software tool called the "Lateralizer" has been developed for piloting and conducting customizable experiments using the divided visual field paradigm. A significant difference between RVF/LH and LVF/RH task performance using the divided visual field paradigm does provide evidence of a functional asymmetry between the two cerebral hemispheres. However, as described by Ivry and Robertson (1998), there are limitations to the types of inferences that can be made from this technique: Visual information