PERSISTENT SENSORY MEMORY AND THE LAW ENFORCEMENT USE OF FORCE.

Law enforcement officers have used force against vehicles and subjects that were perceived as still moving and/or threatening, though in actuality, the subjects may have stopped or paused. How and why does this human perception occur?

“Persistence” is a term used to refer to the influence of the visual or auditory information associated with a stimulus after that stimulus has actually ended. Persistent sensory memory, the first stage of memory, integrates visual information in a continuous stream of images and through visually blank intervals. In effect, the brain “creates pictures in the mind” and/or may continue to perceive, analyze, and respond to a terminated stimulus as though it is continuing. Persistent sensory memories (iconic, echoic, haptic) are very brief. Iconic, or visual memory, is estimated to last less than 1/2 second. Echoic, or auditory, memory may persist for 3-4 seconds, while haptic, or tactile memory, may persist for up to 10 seconds.

Sensory persistence may be influenced by the nature of the stimulus. The longer a stimulus or image is present, the faster that image decays in our persistent sensory memory (Dick, 1974). When the brightness of a stimulus or image is increased, the duration of the associated persistence also decreases. However, a persistent sensory memory is also subject to “masking” effects when another stimulus either during, or immediately following, interrupts and interferes with one's ability to remember the original, persistent sensory memory (Long, 1980). Essentially, new sensory information is blocked out by older sensory information, making it less likely a person will consciously perceive the new information. “Change blindness,” or the inability to detect differences in two successive scenes, occurs when the images are separated by a very brief blank period or interval (Becker, Pashler, and Anstis, 2000). Any recognition of both the old and new information (images) will be dependent on whether the two images are independently meaningful only when masked, or are temporally integrated.

Information persistence is associated with the information about a stimulus that persists after that stimulus ends. In this case, as the time a stimulus is present increases, so does the duration of the brain’s visual encoding (Greene, 2007). The persistence of the non-visual elements of a stimulus can include the intangible features, spatial relationship, and location of the image, though this type of persistence is not believed to be susceptible to masking effects.

QUESTIONS

Is a trained law enforcement officer subject to the influences of persistent sensory memory? Why, or why not?

Could persistent sensory memory influence a law enforcement officer’s use of force? Why, or why not?

Could persistent sensory memory impact a statement provided by a law enforcement officer following a use of force? Why, or why not? If so, would any discrepancies indicate deception?

Could persistent sensory memory life times have any relationship to a law enforcement officer’s reaction times in a use of force? If so, how? If not, why?

Could a witness’ persistent sensory memory influence their perception of a law enforcement use of force and their resultant statement and opinion? Why, or why not? If so, would this indicate deception? Would the statement be accurate? Should the statement be used in determining the reasonableness of the use of force? Why, or why not?

Should the influence of persistent sensory memory be considered when objectively evaluating a law enforcement use of force for reasonableness? Why, or why not?

Does an understanding of persistent sensory memory have an application in evaluating a civilian act of self-defense?

REFERENCES

Becker, M., Pashler, S. and Anstis. (2000). "The role of iconic memory in change-detection tasks". Perception. 29 (3): 273–286.

Dick, A. (1974). "Iconic memory and its relation to perceptual processing and other memory mechanisms". Perception & Psychophysics. 16 (3): 575–596.

Long, G. (1980). "Iconic Memory: A Review and Critique of the Study of Short-Term Visual Storage". Psychological Bulletin. 88 (3): 785–820.

Greene, E. (2007). "Information persistence in the integration of partial cues for object recognition". Perception & Psychophysics. 69 (5): 772–784.

Nikolić, Danko; S. Häusler; W. Singer; W. Maass. (2009). "Distributed fading memory for stimulus properties in the primary visual cortex". PLoS Biology. 7 (12).

Sperling, G. (1960). "The information available in brief visual presentations". Psychological Monographs. 74: 1–29.