Most eyewitness identification is based on observation that occurs under restricted conditions (for example, poor lighti

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Most eyewitness identification is based on observation thatoccurs under restricted conditions (for example, poor lighting,distance, extreme stress, or brief exposure). How accurate arethese identifications and how are they influenced by theselimitations? A recent study examined the influence of distance onthe accuracy of face recognition (Lampinen, Erickson, Moore, &Hittson, 2014). Each participant viewed eight living targets, oneat a time, outside on a flat sidewalk during daytime hours at arandomly selected distance of either 5, 10, 15, 20, 30, or 40yards. After the participant was asked to turn around, a targetindividual was positioned at the assigned distance. The participantthen turned back and looked for 10 seconds before being asked toturn around again. The target individual was then replaced by a newtarget. This procedure was repeated until all eight targets hadbeen seen. The order in which the eight targets appeared was alsorandomized. After viewing all eight targets, the participant wastaken from the viewing area and asked to complete a survey.Finally, the participant was shown 16 photographs, one at a time,in a random order. Eight of the photographs showed the eight targetindividuals, and the other eight photographs showed novel facesthat were selected so that each matched a verbal description of oneof the targets. For each photograph, the participants were askedwhether they had seen or not seen the individual and to rate theirlevel of confidence.
The results showed that the proportion of correctidentifications was around 70% at a distance of 5 yards but droppedregularly as the distance increased to around 55% at 40 yards.Clearly, distance has a significant influence on the accuracy ofeyewitness identification.
Although the results may not be particularly surprising, thisstudy provides a relatively simple and easy-to-understand exampleof experimental research strategy. The researchers manipulated theviewing distance by randomly assigning participants to one of sixdifferent distance conditions. The random assignment also helped toensure that the participant characteristics, such as age or gender,did not differ greatly from one group to another. The location andother environmental conditions were also standardized across thedifferent distance conditions. As a result, the researchers werejustified in making a cause-and-effect conclusion: increasing theviewing distance from 5 to 40 yards causes a significant decreasein the accuracy of eyewitness identification. (Reference: Lampinen,J. M., Erickson, W. B., Moore, K. N., & Hittson, A. (2014).Effects of distance on face recognition: Implications foreyewitness identification. Psychonomic Bulletin and Review, 21(6),1489–1494. doi:10.3758/s13423-014-0641-2)
One of the major learning objectives of this chapter is todescribe the general purpose of an experimental research study,differentiate experiments from other types of research, andidentify examples of experiments.
The goal of experiments is to establish the existence of acause-and-effect relationship between two variables. To accomplishthis goal, the researcher must include the element of manipulationin the experimental study. The researcher manipulates one variableby changing its value to create a set of two or more treatmentconditions. An experiment must demonstrate that changes in themanipulated variable are directly responsible for causing thechanges in the second variable.
In Lampinen et al.’s (2014) experiment, which of the followingvariables are manipulated? Check all that apply.
___Accuracy of face recognition
___Lighting
___Distance from the target
To rule out the possibility of a coincidental relationship,rather than a cause-and-effect relationship between two variables,another critical element of an experiment is the control of allother variables to ensure that they do not influence the twovariables being examined.
In Lampinen et al.’s (2014) experiment, which of the followingvariables are controlled? Check all that apply.
___Distance from the target
___Location and other environmental conditions
In Lampinen et al.’s (2014) experiment, the researchers can bereasonably confident that the changes in identification accuracyare not caused by changes in the lighting or location. Why is thisconfidence justified?
___Lighting and location are randomized across trials.
___Lighting and location are the same for all treatmentconditions.