Developmental Pattern of Digit Span

Developmental Pattern of Digit Span Psychology

So, how can we investigate short-term memory across ages? This is a task Sebastián and Hernández-Gil (2012) sought to tackle in their study on the digit span and the development of the phonological loop. Before we cover the developmental pattern of digit span study, let's take a look at the history of the digit span in psychology.

The digit span test has been used in memory research since the nineteenth century. But, when the Working Memory Model was introduced, we could identify what component of memory it specifically measured.

The history of Memory Research

The first researcher to study memory experimentally was Herman Ebbinghaus. In the nineteenth century, he conducted hundreds of experiments on himself to investigate the mechanisms of learning and forgetting. Ebbinghaus recorded how many nonsense syllables he was able to memorise quickly. Other researchers adapted the nonsense syllable span procedure, which evolved into the digit pan test, similar to the one we use in research today.

Joseph Jacobs (1887) was one of the first to investigate the number of items short-term memory can store using the digit span test.

• Jacobs presented participants with sequences of digits that were increasing in length, up to a point when the sequence was too long for the participant to recall.
• According to his experiments, adults could recall sequences of, on average, 9.3 items.

Developmental Pattern of Digit Span Definition

The digit span test is used to test the capacity of short-term memory, specifically the phonological loop. The procedure can be described as follows:

• The experimenter presents a sequence of digits to a participant.
• If a participant can successfully repeat a sequence of four digits back, the experimenter will present them with a longer five-digit sequence.
• The experimenter will present longer sequences until the participant can no longer accurately recall the sequence.

Short-term memory is a temporary memory store that holds information after it is presented. Short-term memory has a limited capacity; it can only store a few items at a time. Here, an item refers to a meaningful chunk of information.

Developmental Pattern of Digit Span Model of Working Memory

According to Baddeley and Hitch's (1974) Working Memory Model, the short-term memory store consists of the central executive, visuospatial sketchpad, and phonological loop.

• The central executive is responsible for allocating attention to other components and performing cognitive tasks like decision-making and problem-solving.

• The visuospatial sketchpad is the inner eye of the system; it stores visual and spatial information.

• The phonological loop is the inner ear; it is responsible for holding and reactivating verbal information using inner speech.

The image shows how verbal information, in the case of the digit span test it's the sequence of digits, is passed onto the phonological loop, where it is briefly stored.

Sebastián and Hernández-Gil (2012): Developmental Pattern of Digit Span Theory

Short-term memory changes throughout our life. The digit span task allows us to measure and compare these changes. Sebastián and Hernández-Gil's (2012) investigated the effect age has on the development of the phonological loop.

The researchers aimed to investigate patterns of phonological loop development across the ages of 5 to 17. They administered the digit span test to 570 Spanish children without any hearing, reading, or writing impairments. The digit span test was used to see how children’s ability to hold information in short-term memory changes with age and to compare this data with previous studies conducted in the UK.

The results demonstrated a continued increase in digit span across ages, suggesting that working memory develops until the age of 17.

In early childhood, we observe lower digit spans, that increase throughout adolescence. This is because as children learn to process information faster with age. Moreover, around the age of six, children begin to use rehearsal to refresh the information stored in short-term memory. Children start to rehearse using the inner voice component of the phonological loop. This prevents forgetting of items and improves their digit span.

The Effects of Old Age on Short-term Memory

Old age appears to affect working memory significantly. Comparisons of the Sebastián and Hernández-Gil data with earlier studies on the elderly showed that healthy elderly participants have a digit span similar to a seven-year-old. Older people with conditions like dementia have only slightly lower digit spans, corresponding to a typical six-year-old.

Evaluation of Sebastián and Hernández-Gil (2012)

Important evaluation points of Sebastián and Hernández-Gil (2012) to consider are:

• The Sebastián and Hernández-Gil study used a standardised procedure, making their study easy to replicate, and increasing the reliability of the study.

• They recruited a large, representative sample and excluded participants with cognitive impairments that could impact the results. The results for the Spanish study are generalisable to the Spanish population, considering the large sample size (570).

• The task was completed at school, during the breaks, which on the one hand, is a familiar environment for children, but on the other, allows for certain disruptions like loud noises.

• The task itself could be criticised as being artificial, suggesting low task validity; we don’t usually use our short-term memory to recall sequences of numbers in real life. However, using the digit span tasks allowed researchers to make comparisons to data from English studies.

Generalisability of Sebastian and Hernandez Gil (2012)

Previous English developmental research showed that digit span increases in children until the age of 15, after which it remains constant. At 15, the Anglo-Saxon participants acquired adult levels of short-term memory capacity. English studies also demonstrated generally higher digit spans for children.

One explanation of these results is the length of words for Spanish digits, which tend to be longer than words for English digits.

Longer words can’t be rehearsed as many times as shorter words using inner speech. The difference in digit span only appeared after the age of six, when children start to use inner speech to rehearse information, supporting the word length explanation for the differences. Overall, we can see that language used can affect the generalisability of digit span research findings.