ADHD and Memory: Forgetting to Remember

Attention Deficit Hyperactivity Disorder (ADHD) is often misunderstood because many of the characteristics associated with ADHD, like attention problems and forgetfulness are symptoms that everyone experiences from time to time. A current song by Francesca Battistelli opens with “I’ve lost my keys in the great unknown, and call me please cause I can’t find my phone” (Battistelli, 2011). This statement could be about anyone at one time or another but for those with ADHD, it may be more often unless they find ways to manage their symptoms. This paper aims to better understand how forgetting to remember affects those with ADHD.

Individuals with ADHD suffer from problems with attention, impulsivity and hyperactivity and the consequences of these deficits can affect all aspects of life (Re, Franchis, Cornoldi, 2010). ADHD is diagnosed using different subgroups including ADHD-Combined and ADHD-I (Castel, Lee, Humphreys & Moore, 2011). The ADHD-Combined subtype exhibits problems with attention, impulsivity and hyperactivity whereas the ADHD-I subtype exhibits problems with attention primarily. Studying memory and ADHD may better help us understand the differences between the three.

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The process of forming new memories begins when we first pay attention to something. The dual-component model defines working memory as two related processes: holding new information in the primary memory (PM) and retrieving information from secondary memory (SM) (Gibson, Gondoli, Flies, Dobrzenski, & Unsworth, 2010). This paper will examine current research on ADHD and working memory by reporting on three recent studies in which working memory is the dependent variable and group (ADHD vs. non-ADHD) is the independent variable. The studies examined progress from the youngest participants to oldest.

The first study assessed a group of 5 year olds, the second study examined 6-9 year olds and the third study examined 11-14 year olds. Evidence presented in these studies provides evidence for the persistence of memory problems throughout the school age years in children with ADHD. Working memory problems are associated with ADHD and may be identified as early as age five years according to a recent research study in Italy (Re, et al. , 2010). The authors used a visuospatial working memory task to determine if children with ADHD had trouble remembering certain information while other distracting information was presented.

They hypothesized that children with ADHD would not score as well on this type of memory task. This study sought to find out more about working memory problems in pre-school children to improve early interventions. In Re’s study, 46 five year old students were divided into two groups. A total of 23 students without ADHD comprised the control group and 23 students diagnosed with ADHD comprised the second group. ADHD diagnosis was confirmed using the “Identificazione Precoce del Disturbo da Deficit di Attenzione/iperattivita per Insegnanti” (IPDDAI) reported by teachers and the IPDDAG reported by parents.

The groups had equal numbers of boys and girls. IQ and socioeconomic status were controlled. The test used to test memory in Re’s research was the Dual Request Selective Task (DRST). The test was a piece of paper with 16 squares drawn on it. One of the squares is red. The tester then uses a plastic frog to jump across the paper landing on random squares until he eventually lands on the red square. There are two tasks for the children to complete as part of the test. The first task was to clap hands when the frog lands on the red square. The second task was to remember which square the frog landed on first.

Testers gave thorough instructions and practiced with just the clapping step first. Then once they knew the first step was understood they added the instructions for the second step. The test was administered ten times gradually using a greater number of frog jumps which were between 2 and 6 jumps. Results of the frog test showed that the ADHD group scored significantly lower. Specifically the children in the ADHD group clapped at the wrong time more often and had more trouble remembering which square the frog started on. Re and colleagues noted that the distraction of holding two tasks in mind created errors in both tasks.

The results included two types of errors. Errors of intrusion, where the participants were unable to remember only the relevant information and errors of invention where participants remembered information not presented. The group with ADHD performed a greater number of errors of both types and particularly intrusion errors which may be a result of not being able to inhibit information (Re. , et al. , 2010). In addition, the study examined the relationship between the initial ADHD diagnosis score and the memory test score and found evidence that the degree of symptoms was correlated with the degree to which memory scores dropped.

This study may demonstrate that children with ADHD have problems remembering information when there is more than one thing to remember. The next study examines similar research in that the memory test also has two tasks placed on the memory simultaneously. A recent study researching memory and ADHD compared groups with ADHD combined type, ADHD-I and a control group and found that individuals with ADHD combined type did not perform as well on memory tasks (Castel, et al. , 2011). The goal of this study was to gain a better understanding of the relationship between working memory and ADHD.

In addition, researchers hoped to better understand the memory process by looking at how individuals would respond to memory tasks that also had a point earning component. The researchers hypothesized that the groups set forth in this study, including the control group, would not greatly differ in word recall ability. They also hypothesized that the children diagnosed with ADHD would not perform as well on the points earned task. In addition the researchers were evaluating whether the points earned task could be learned with practice. Castel’s study included 116 children ages 6-9.

A total of 57 children had been diagnosed with ADHD and 59 did not have ADHD. Of the 57 children with ADHD, 25 were diagnosed with ADHD-I and 32 had the Combined subtype of ADHD. Diagnoses were validated using the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DISC-IV) assessments provided by parents and collaborating assessments from teachers. All children had an IQ score of 70 or higher verified by testing on the Wechsler Intelligence Scale for Children IV (WISC-IV). Reading ability was also controlled to ensure the children had similar reading abilities.

Students were asked to recall words that were assigned different numbers of points in order to try to get as many points as possible to earn a small reward. The researchers explained to the children that this would be done by remembering the words that had the highest points. They were also given an example. To begin, 12 words matched with a corresponding point value between 1 and 12 points were presented on a computer screen in two second intervals. At the end of the list the children were prompted with the word “remember” and then had thirty seconds to verbally list the words they remembered.

This was repeated 12 times with 12 different lists. As hypothesized, all groups performed comparably on the word memory recall portion of the test. In addition, all groups improved their performance with practice, scoring higher on subsequent recall tests. Another commonality showed that each group remembered more high point words than low point words; however, there were significant differences between groups in the amount of points earned with the ADHD-Combined group scoring significantly lower points.

This finding demonstrated a deficit in memory function as related to remembering the items with the added task of remembering the words with the highest points. The results of the second study build on the previous research demonstrating that when a second task is loaded onto the working memory, deficits become apparent. In addition, this study demonstrated that the participants with the combined type of ADHD scored lowest which supports findings in the first study where participants with higher diagnostic ADHD scores had lower scores.

The third study examines working memory and tries to understand where this deficit occurs. Recent research has shown that individuals with ADHD exhibited deficits in secondary memory using verbal and spatial recall tests to tests memory (Gibson et al. , 2010). Researchers used data obtained from a verbal and spatial memory test to determine if there was a difference in performance using primary memory and secondary memory. Primary memory is defined as temporarily holding new information being and secondary memory involves recalling stored information.

Gibson and colleagues accomplished this by examining what strategy participants used to remember items in a list. Participants either used the “recency” strategy which means they remembered the words or locations at the end of the list (the most recent), the “pre-recency” strategy which means they remembered the words or locations at the beginning of the list or they used a combination of the two. The memory test results were then evaluated within these contexts. The researchers hypothesized that participants with ADHD would score lower on primary or secondary or both types of memory performance.

Gibson’s study included 63 children, 11-14 years old from a sample of middle school students (1938 total). This age group was chosen to ensure individuals were capable of this kind of test. IQ was assessed using the Wechsler Abbreviated Scale of Intelligence (WASI) and participants met a score of 70 or above, although it should be noted that the average IQ in the ADHD group was slightly lower. ADHD was confirmed or discounted using the DISC IV dividing participants into ADHD and non-ADHD groups. Subtypes of ADHD were not separated, but placed in one ADHD group.

Participants taking medication for ADHD did not take medicine during the testing period. There were two memory tests. In the first test, 12 words presented one at a time in one second intervals were viewed on the screen. At the end of the list, participants verbally listed in any order what words they could remember. This was repeated 15 times using different lists. The second test was spatial and tested memory of what blocks changed color. A total of 36 white blocks were viewed on a screen. The blocks changed colors from white to red for one second each.

After 12 blocks changed color, participants tried to remember the location of the blocks that had changed color by clicking the mouse on where they thought the blocks had been. Any order was accepted. This was repeated 15 times, like the first test. Participant’s responses were evaluated to determine their memory strategy; “recency”, “pre-recency” or “combined”. Memory strategy was determined by looking at the participant’s plot of responses. If most of the responses were from the end of the list, a “recency” approach was assigned and if most of the responses were from the beginning of the list, a “pre-recency” approach was listed.

If the responses varied, a “combined” approach was listed. These assignments were then used in evaluation of the results. Results showed that the ADHD participants scored equally well as controls when recalling information using the “recency” strategy but not nearly as well as controls when using “pre-recency” strategies. This means that they were able to remember a comparable number of items from the second half of the list but not from the first part of the list. These findings suggest that individuals with ADHD may have deficits in regards to secondary memory.

The slight variance in IQ was not found to be significant. In summary, all three studies give evidence that children with ADHD have problems with working memory. In addition, the working memory problems persist across broad age groups. Another commonality found in the first two studies the correlation between increased prevalence of ADHD symptoms and poorer performance on memory tests. These studies begin to narrow down and define the problem of working memory in individuals with ADHD. The first two studies demonstrated that memory problems were prevalent when a second memory task was added.

In addition, the second and third studies demonstrated that memory capacity was not affected when another variable was not present as demonstrated when groups with ADHD were able to recall as many words as the other groups. More research should be done on memory and ADHD including testing long term memory to see if children with ADHD are retaining learning the same as their peers. Memory research should include adults with ADHD to understand if memory problems persist or improve. If they improve, is it due to compensations that can be taught earlier?