In Experiment 3 of Moray's (1959) study on auditory attention, how was the independent variable manipulated to investigate the effect of expectation (cognitive set) on the recall of digits?
By preceding the digits with the participant's own name for one group, and preceding them with a neutral warning instruction for the other group.
By instructing one group of participants that they would be asked questions about the shadowed message, and another group to listen for and remember any digits they could.
By presenting some participants with a repeated list of digits in the rejected message and other participants with non-repeated digits.
By varying the rate at which digits were spoken (either at a fast tempo or a slow tempo) in the unattended ear.
