In 1978, researchers premack and woodruff published a study in science magazine, reporting an experiment where an adult chimpanzee named sarah was shown videotapes of eight different scenarios of a human being faced with a problem. after being shown each videotape, she was presented with two photographs, one of which depicted a possible solution to the problem. for example, a problem might be a human trying to grab an object just out of reach. the picture of the correct solution would show the human stepping on a box to be able to reach further. in the experiment, sarah picked the photograph with the correct solution seven times out of eight. if sarah were simply guessing, for how many of the eight problems would you expect her to correctly identify the possible solution?