When our senses initially take in a stimulus, it is first stored in the sensory memory stage. Our entire surroundings are experienced by the senses, so the sensory memory holds vast information about our environment. Because it holds so much information, the sensory memory stage retains this information for only a small period of time. Visual stimuli are stored in the iconic memory, a brief image lasting a quarter to a half of a second. Auditory stimuli are stored in the echoic memory, a sound lasting roughly four seconds. Haptic (or tactile) memory is the memory of touch, typically lasting around two seconds. With this large but brief storage of information, our brains decide which stimuli are important to focus on. The mind then focuses on the critical stimuli in the sensory memory, encoding them and moving them to the next level, short-term memory.
Some proponents have suggested that sensory memory does not exist. The brain simply takes in sensory information and adds relevant information to the short term memory. Sensory memory is an unnecessary subgroup that over-complicates the matter; sensory information either moves through our senses and is forgotten or is focused upon and remembered.
[P1] The senses detect stimuli. [P2] The brain briefly stores all sensory stimuli in sensory memory. [P3] Stimuli deemed important can be focused on and remembered; others are forgotten within a few seconds.
Rejecting the premises
[Rejecting P2] Sensory memory isn't real; it is just the beginning of short term memory.