Can People Hold 7±2 Objects in their Short-Term Memory or What?

Seven

Is the magical number 7 so magical, after all?

Myth: People can hold 7±2 objects in their short-term memory.

Fact: English-speaking people can on average hold 7±2 unidimensional objects in their short-term memory.

One of the most cited papers in psychology is: “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” by George A. Miller (1956).

The findings by Miller are often referred to as Miller’s Law or Miller’s Magical Number 7. In his research, Miller found out that adults are able to hold between 5 and 9 items in their short-term memory (STM).

But it is relevant to note that Miller’s Magical Number 7 was related to so-called unidimensional objects, which Miller himself emphasizes in a letter:

“… 7 was a limit for the discrimination of unidimensional stimuli (pitches, loudness, brightness, etc.) and also a limit for immediate recall, neither of which has anything to do with a person’s capacity to comprehend printed text.”

Outside the laboratory, however, we are often faced with multidimensional objects that differ from one another in several ways, which makes the objects easier to remember as we can distinguish and chunk multidimensinoal information (e.g., words) into meaningful pieces.

The point is that we cannot distinguish unidimensional objects so easily as they only differ from one another in one way (e.g., sounds) — unless we are very skilled musicians? So, it is likely that we can hold more multidimensional, compared to unidimensional, information in our STM.

People’s native language also influences how much information they can store in their STM. In a conference paper, Derek M. Jones (2002) states that:

“It turns out that the kind of STM people use for remembering digits is based on the sound of those digits … A person has a two second, approximately, capacity limit on the amount of sound they can hold in STM. Approximately 7±2 English digit words can be spoken in approximately 2 seconds.” (p. 2)

So, the value 7±2 as a measure of STM only applies to English-speaking people who try to remember a sequence of digits. We know that people with different languages have different speech rates, and therefore, we would expect that faster speech rates enable readers to hold more information in their STM.

Indeed, research supports this idea. The Chinese language enables readers to increase their STM capacity to an average of 9.9 digits, whereas Welsh readers have a STM average capacity of 5.8 digits due to their slow speech rate (Jones, 2002).

What can we learn from these findings? Well, it is not easy to estimate how well people perform on memory tasks as people’s STM capacity depends on various factors.

We know that people’s speech rates (English vs Chinese), the type of information/objects (uni- vs multidimensional), and the familiarity of objects, influence how well people perform on memory tasks.

Photo: Kevin Schraer