The monkeys were usually caged in pairs, so they could see what sort of treatment another monkey was getting. When one monkey was rewarded with a grape but another monkey was only offered a piece of cucumber for the same task, the monkey offered the cucumber would often refuse to take part in the trial further. For example, the monkey might won’t give the pebble, won’t accept the cucumber or even toss the cucumber or pebble onto the ground in obvious exasperation. These behaviors aren’t typically observed in monkeys who are not comparing their treatment compared to that of another pet.They describe that neurofibrillary tangles are among the physical hallmark indications of Alzheimer’s disease, and have been shown to contribute to disease progression in people under chronic tension conditions during the course of past studies. Chronic stress is positively linked to physical brain changes leading to Alzheimer’s, dementiaThe study group, using a mouse-based model, noted ‘we found that repeated episodes of emotional stress, which has been demonstrated to be comparable to what humans may experience in ordinary life, led to the phosphorylation and changed solubility of tau proteins in neurons. These events are critical in the advancement of NFT pathology in Alzheimer’s disease.’ Researchers determined that the result was most pronounced in the hippocampus of the brain, an area from the formation, organization and storage space of memories.