Paradox of memory: can last lifetime or gone tomorrow, unable to remember something want to recall, incapable of ignoring what you would like to forget. Psychologists use memory models to think and communicate about memory. Most info from sensory to stm to ltm, then back to stm for retrieval. Brief storage of perceptual information before passed to stm. Retains info in active, conscious state for limited duration. Informational persistence: know some things about stimulus after gone. How much information can one perceive from single glance. Touch: tacton lasts less than a second. Allows recognition processes more time to operate. Retrograde amnesia: forget things happened before trauma. Anterograde amnesia: inability to remember things after trauma. Mistake by thinking of something that sounds like actual term. Hippocampus damaged, affects transfer between stm and ltm. Declarative (explicit or know that memory) rather than procedural ( or know how knowledge) seems to be affected. Chucking: use ltm to organize info in stm.