My Cat Seems Mentally Slow. In the wild, this instinct can protect them from predators or other cats that might be a threat. She's a little large, but closer to average.
Sometimes lethargy is due to old age in cats. If your cat's behavior seems off, it could be ill or could have a more serious problem with its nervous system. When a cat appears to be confused, disoriented, or unable to process information as quickly as other cats, the reason isn't necessarily substandard intelligence.