114 Understanding Rational Decision Making
were given special headphones to wear that allowed them to hear two different conversations
spoken into each ear simultaneously. Listeners had to selectively attend to one conversation and
tune out the other. The only thing listeners could remember about the conversation they tuned
out was whether the speakers were male or female. Listeners were not able to tell which language
was spoken or to remember any words. In a follow-up study, listeners not only had to listen to two
conversations simultaneously and selectively attend to one conversation, they also had to listen for
a target word in both conversations.^87 Although listeners recognized the target word when it was
spoken in the conversation they attended to, they did not recognize it when it was spoken in the
unattended-to second conversation.
Nonetheless, listeners may perceive a fraction of the words they do not attend to. Listenerswho are asked if they recall target words from an unattended conversation immediately after each
target word is spoken are able to recall the target words 25% of the time.^88 Although listeners
can perceive two simultaneous messages simultaneously, they can only attend to one message at a
time. Thus, an unattended-to message delivered simultaneously can still divert a listener’s attention
to it, especially if it is loud, important to the listener, or relevant to the message the listener was
attending to.^89
Constraints on Visual Attention
Viewers’ visual attention works very much like listeners’ auditory attention. When viewers attend
to one set of simultaneously presented images, their processing of the other set drops off. In one
experiment, viewers watched a video that showed a set of objects in silhouette moving from left
to right and another set moving from right to left at the same time. The objects were large, easy to
see, easy to identify, and were semitransparent so they could be seen even while they passed through
each other. When viewers were asked to attend to objects moving left to right, they were able to
recognize all those objects easily. The same was true for viewers asked to attend to objects moving
right to left. However, the fi rst group of viewers could not remember anything about the objects
that moved right to left. Neither could the second group remember anything about the objects that
moved from left to right.^90
Readers can perceive unattended written words but do not consciously remember them.In a study that demonstrated the interplay between perception and attention, scientists gave
mild shocks to readers as they showed them different words. The scientists then presented
those same words to the readers, but out of the focus of their attention. Although the readers
did not attend to the words or consciously recognize them, it was clear they still perceived
the words because they gave galvanic skin responses when the words were presented to them
a second time.^91 In a similar way, nonfocal information in print ads can infl uence consumers’
evaluations of brand names even when consumers do not attend to or consciously recognize
that information.^92
One situation exists in which audience members can attend to two stimuli at the same time,and that is when the two stimuli are presented in different perceptual modes. Audiences who are
presented with visual and auditory information in rapid succession are able to begin processing
the auditory information about 60 milliseconds before they fi nish processing the visual informa-
tion.^93 Similarly, audiences can identify one visual and one auditory stimulus even when the two
stimuli are presented simultaneously.^94 Consequently, students in online geometry courses learn
more when audio, as opposed to on-screen text, is used to describe the geometric diagrams dis-
played on their computer screens.^95 However, attending to two stimuli simultaneously presented
in two different modalities is diffi cult for anyone if both stimuli consist of verbal information. For