Internal memory cues are patterns of thinking that help trigger a specific memory. For example, mental imagery, which involves visualizing a certain scene happening, can serve as an internal reminder of an event that happened.
External memory cues are objects or events that trigger a memory that they are associated with. For example, a glass of water next to your bed is an external reminder to drink water when you wake up.
Ever since we've had things to remember, we've set reminders. Whether it's the ding of an app or a string tied around your finger, memory devices help offload our need to remember everything all the time. But there's a downside to all those reminders.
When the sum total of human knowledge rests an arm's length away in each person's pocket, why do we have to remember anything anymore? On an average day most of us check our smartphones 47 times, and nearly double that if we're between the ages of 18 and 24, which might explain why some of us have such a hard time processing the information we take in to form memories.