Many psychology students learn that the capacity of short-term memory is 7 ± 2. However in the cat book we review evidence that in fact it would be more accurate to say 4 ± 2 (see page 6, review by Cowan, 2001). In fact recent research has found that there is a link between this capacity and IQ – people with high IQs have greater STM capacity.

What does this all have to do with the iPhone (I hear you ask)? The new four-gigabyte iPhone can hold 1,000 songs if they are the normal length (about 4 minutes) but this capacity would be drastically reduced if the songs are each 20 minutes long. Is the same true for human STM? At the University of Oregon, psychologists have produced some surprising answers from recent research (full text of the article). They found that complexity of items didn’t seem to affect capacity – people could hold four items in their memory even if they were very complex. What was affected was the clarity of the memory. They also found that those people who could hold more items in their memory actually had less clear memories for the individual items. So even though people with high IQs can think about more things at once, the quality of the memories may not be that good.

But which is better, the brain or the iPhone? Any thoughts?