Capacity

• What are the strengths of capacity?

  1. Valid evidence
• What are the limitations of capacity?

  1. May be overestimated
• Strength (capacity) = valid evidence

  • Jacobs’ (1887) study is a very old one and early research in psychology often lacked adequate controls
  • For instance, some participants’ digit spans might have been underestimated due to confounding variables, such as being distracted during testing or procedural elements
  • However, Jacob’s findings have been replicated and confirmed by others in more highly controlled environments since the 1800s
  • Despite the age of Jacobs’ study, it was a valid test of digit span in STM and was influential in understanding of how STM processes and holds information
• Limitation (capacity) = overestimated capacity

  • Miller (1956) proposed that humans can effectively process no more than seven chunks of information, plus or minus two pieces of information, at any given time
  • However, research suggests that number was meant more as a rough estimate
  • Cowan’s (2001) extensive review of varied STM capacity research, posits that there is a more precise capacity limit - four (plus or minus 1) chunks
  • Lack of certainty regarding capacity of STM reduces reliability of studies in this area