dimensional people and objects, and decide what actions might be appropriate
with respect to them. In the laboratory, in contrast, the emphasis, according to
Tipper et al. (1992, p. 902), is on ‘‘experiments that briefly present static 2D
displays and require arbitrary responses. It is clear that such experimental sit-
uations are rarely encountered in our usual interactions with the environment.’’
Tipper et al. (1992) carried out a series of experiments under fairly naturalistic
conditions. As their findings resembled those obtained in traditional laboratory
studies, the artificiality of most laboratory research may not always undermine
its validity.
Focused Auditory Attention
Systematic research on focused attention was initiated by the British scientist
Colin Cherry (1953). He was working in an electronics research laboratory at the
Massachusetts Institute of Technology, but somehow managed to find himself
involved in psychological research. What fascinated Cherry was the ‘‘cocktail
party’’ problem, i.e. how are we able to follow just one conversation when
several different people are talking at once? Cherry discovered that this ability
involves making use of physical differences to select among the auditory mes-
sages. These physical differences include differences in the sex of the speaker,
in voice intensity, and in the location of the speaker. When Cherry presented
two messages in the same voice to both ears at once (thereby eliminating these
physical differences), listeners found it remarkably difficult to separate out the
two messages on the basis of meaning alone.
Cherry also carried out experiments in which one auditory message had to be
shadowed (i.e. repeated back, out loud) at the same time as a second auditory
message was played to the other ear. Very little information seemed to be
extracted from the second or non-attended message. Listeners seldom noticed
whenthatmessagewasspokeninaforeignlanguageorinreversedspeech.In
contrast, physical changes such as the insertion of a pure tone were almost al-
ways detected. The conclusion that unattended auditory information receives
practically no processing was supported by other evidence. For example, there
is practically no memory for words on the unattended message even when they
are presented 35 times each (Moray, 1959).
Broadbent’s Theory
Broadbent(1958)feltthatthefindingsfromtheshadowingtaskwereimpor-
tant. He was also impressed by data from a memory task in which three pairs of
digits were presented to a subject dichotically, i.e. three digits were heard one
after the other by one ear, at the same time as three different digits were pre-
sented to the other ear. Subjects demonstrated a clear preference for recalling the
digits ear by ear rather than pair by pair. In other words, if 496 were presented to
one ear and 852 to the other ear, recall would be 496852 rather than 489562.
Broadbent (1958) accounted for the various findings by making the following
assumptions (see figure 15.2):
.Twostimuliormessagespresentedatthesametimegainaccessinpar-
allel (i.e. at the same time) to a sensory buffer.Attention and Performance Limitations 365