An eyewitness testimony is a statement given under oath by a person present at an event who can describe what happened. During circumstances in which a child is a witness to the event, the child can be used to deliver a testimony on the stand. The credibility of a child, however, is often questioned due to their underdeveloped memory capacity and overall brain physiology. Researchers found that eyewitness memory requires high-order memory capacity even for well-developed adult brain. Because a child's brain is not yet fully developed, each child witness must be assessed by the proper authorities to determine their reliability as a witness and whether they are mature enough to accurately recall the event, provide important details and withstand leading questions.
Brain development associated with eyewitness testimony Brain development is an after-forward process; from the occipital lobe (visual), to the temporal lobe (sensory, auditory and memory), to the parietal lobe (motor, pain, temperature, and stress), and finally to the frontal lobe (language, reasoning, planning, and emotion). All of these brain regions work together to build up our eyewitness memory.
Generally, infants are born with formed brain systems and their brains develop very rapidly during the first three years. The size of a newborn brain is approximately 400g and continues to grow to 1100g at the age of three, which is close to the size of an adult brain (1300-1400g).
Although infants are born with a properly formed brain, they are still far away from full development. The glial cells, which play a vital role in proper brain function (e.g. insulating nerve cells with myelin), keep growing to divide and multiply after birth. However, to have a fully developed eyewitness memory, the development of gray matter, white matter, the dentate gyrus and density of synapses are highly necessary.
The volume of white matter starts its linear increase from age four to 20, but cortical gray matter is decreases in the parietal, occipital and temporal regions starting from age four, continually changing until after age 12. The development of the dentate gyrus starts forming at 12 to 15 months in the hippocampus, which is essential for the formation of declarative memory in eyewitness testimony. After the formation of the dentate gyrus of the hippocampus, the density of synapses in the prefrontal cortex, which is involved in eyewitness memory, is peaks in its development during 15 to 24 months, changing until the age of adolescence.
Major brain regions necessary for eyewitness performance
Hippocampus The hippocampus is one of the brain structures located within the medial temporal lobe and is considered one of the main structures of the brain associated with eyewitness testimony because it is the area that is important for the formation of long term memories. Declarative memories are long term memories that can be consciously remembered, which include: specific events and factual knowledge. Eyewitnesses use declarative memories, specifically episodic memory, when they are asked to recall specific events that took place in the past. For example, "Do you remember what the doctor said to you last time you visited him?" Research on children as eyewitnesses found that children do not have accurate long term memories for past events.
The hippocampus is not yet completely developed until 2–8 years of age; however, there are mixed findings for the exact moment when the hippocampus stops maturing. Though the hippocampus may stop maturing at a certain age, behavioural evidence shows that declarative memories are known to develop from childhood up until adulthood.
A study looking at age differences in which children can remember episodic memories (e.g. their first day of school, attending a friend's birthday party), elementary and preschool students were questioned about delay interval in past experiences and found significant differences in what children recall. Elementary school students were more successful at this task than preschoolers. Overall, children need more prompts to remember past events and recall fewer details than older children.
Stress also appears to disrupt the function of the hippocampus, as it reduces the likelihood for details to be remembered in a logical sequence. Since most children are asked to recall stressful events for eyewitness testimonies, they may explain them in fragmented sequences of events.
Prefrontal cortex The prefrontal cortex is another brain region involved in eyewitness testimonies. Its function in relation to memory is to create memories that are vivid and that have a lot of contextual detail. Research in the Journal of Law and Human Behaviour found that the ability for child eyewitnesses to accurately recall details of events increases with age, as did the ability to answer specific questions, identify the confederate and resist suggestion. Studies have found that children tend to give few details of the event and sometimes distort them in eyewitness testimonies. This brain region is one of the last regions to develop.
Short term memory occurs in the prefrontal cortex. Working memory is another process that relies on the prefrontal cortex.
Temporal lobe The temporal lobes are involved in several functions of the body including: hearing, meaning, auditory stimuli, memory, and speech. They also play a role in emotion and learningLehr, R. (2011). Brain Functions and Map. Retrieved from http://www.neuroskills.com/brain-injury/brain-function.php and are concerned with processing and interpreting auditory stimuli. This is a major location for memory storage and is associated with memory skills.
Parts of the temporal lobe show late maturation. These regions are of the last brain regions to mature. The gray matter in the temporal lobe continues developing until it reaches its peak development at age 16 for both males and females.
Amygdala The amygdala is located deep within the temporal lobe of the brain and is involved in the acquisition and retrieval of information on highly salient events. It is also involved in several functions of the body, which include determining what and where memories are stored in the brain. The determination of what/where memories are stored is dependent on how big of an emotional response an event evokes. This is related to eyewitness testimonies because young children usually have poorer recall for details of events, but when an event evokes a highly averse response (unpleasant, arousing), they tend to remember it.
The amygdala does not stop developing until late adolescence. Research studies have found that in normal developing children, the volume of amygdala increases substantially between seven and 18 years of age. This influences how children perform as eyewitnesses because children will have poorer skills for storing and recalling memories of events prior to the age of seven.
Short term memory Short term memory is defined as the ability to store information for a short period of time. If it is rehearsed enough, it will be transferred into long term memory. This is important to know in regards to eyewitness testimonies because children have problems transferring short term memories to long term, as discussed previously.
Overall, there are a number of differences in memory among adults and children. With regards to short term memory, a child's capacity to store items is less than that of an adult. More specifically, evidence has shown that a five-year-old can only store up to five items in short term memory, whereas adults are able to store around seven items. This can play a role in how accurate a child's memory performance is in comparison to an adolescent or an adult's recall of the same crime scene.
The amount of time elapsed from when the child witnessed the scene to when they give their testimony is also a contributing factor to how short term memory influences the accuracy of their recall as an eyewitness.McCauley, M., & Fisher, R. P. (1996). Enhancing children's eyewitness testimony with cognitive interview. Oxford, England: Walter De Gruyter Inc. It was found that a child's short term memory is more susceptible to interference as the amount of time increases between the event and the testimony. This can lead to misinformation on the child's part and an inaccurate recall of events. One explanation for this is that information that is learned shortly after the event is combined with information that is being temporarily stored in short term memory, having yet to make it into long term memory, causing contradictory traces to coexist.
Long term memory Eyewitness testimonies in long term memory can be influenced by the loss of information during the process of encoding and storing event details into long term memory. According to the information processing model, if sensory information about an event is not directly transferred from short term memory into long term memory, the information is difficult to retrieve. Research has also found that the rate of transfer of sensory information from short term to long term memory is related to age of the witness. Older children have higher success rates in transferring memory from short term to long term than younger children, which plays a role in why younger children have poorer recall in eyewitness testimonies.
Selective attention also contributes to the impairment of younger children's information encoding process. Namely, if children's attentions are disrupted by an object (e.g. a gun) while witnessing a crime, they might be unable to fully encode all of the details, resulting in poor recall of the event later on in life.
Factors affecting eyewitness testimony
Retroactive interference
Retroactive interference encourages incidental forgetting, in which the newly learned information impairs the retrieval of previously learned knowledge, especially for similar and related information. For example, if you have already learned about proactive interference and recently learned new information about retroactive interference, the knowledge you learned about retroactive interference has the tendency to impede the retrieval of the knowledge of proactive interference.
The passage of time is not of major importance but still has relevance to retroactive interference. The results of a study on rugby players by Hitch and Baddeley showed that trace decay contributes relatively nonsignificant effects on retroactive recall.
Consolidation of the previously learned knowledge and the new information is important. If the previously learned knowledge is well consolidated in memory, the impeding influence caused by the new encoding has less effect; inversely, if the newly learned information is better encoded than the old knowledge, the interference is greater. This is especially true when the previously learned knowledge is simply encoded in short-term and working memory—basically, the low level of consolidation. The similarity between the new information and old knowledge can have an effect on performance as well. When the recently acquired information is phonologically and semantically similar with the known knowledge, the rate of retroactive interference is increased through confusion between the two materials.
The encoding process, retrieval traces and contextual cues of the newly learned information play significant roles in impairment. The ways that information is encoded can impair the retrieval performance of that information. The better encoding, the better retrieval will be, especially under circumstances of appropriate retrieval traces and sufficient contextual cues. How to retrieve the encoded information, a.k.a. retrieval strategy, is also essential for preventing retroactive interference. The failure in binding and tracking the contextual information has an increased impact on the retroactive interference effect.