Some amazing speeches such as some TED Talks viewed by over 10 million people, are slide-less. However, those speeches generally leave the audience with a feeling or a new, strong-yet-singular understanding. Several studies have shown that including images in presentations increases viewers' recollection and positive attitudes concerning the material displayed. In a Purdue University study in which 110 undergraduate students viewed videos, Carmichael, Reid, and Karpicke found the versions of presentations containing graphics resulted in improved judgement of learning, engagement with the speaker, interest in the speaker, and enhanced student memory. In a Stanford University study, Kessel found visualizing information can enhance cognition, schematize and reduce complexity, assist problem solving, enhance memory, and facilitate discovery, but only if the visualizations are applied effectively. Photos from many different photographers can still look like a unified collection, whereas it is harder for a single illustrator's offerings to meet all the needs.