jacobs - AO3

• controlled for extraneous variables - he did not include 7 or W as these are made up of two syllables and so could be more/less memorable than the others which could affect results. study has high internal validity.
• supported by miller who found STM held a similar amount of info. Jacobs findings of STM are reliable.
• may be incorrect - his research was reviewed and it was concluded the capacity of STM is only about 4 chunks which suggests inconsistency in the research.