is number every time.

Summary of the Laws of Attention

Bringing together now what we have learned regarding the higher and
more difficult forms of attention, as revealed by sustained attention
and work under distraction, by the span of attention and by trying to
do two things at once, we find the previously stated three laws of
attention further illustrated, and a couple of new laws making their
appearance.

(1) The _law of selection_ still holds good in these more {263}
difficult performances, since only one attentive response is made at
the same instant of time. Automatic activities may be simultaneously
going on, but any two attentive responses seem to be inconsistent with
each other, so that the making of one excludes the other, in
accordance with the general law of selection.

What shall we say, however, of reading four disconnected letters at
the same time, or of seeing clearly four colors at the same time?
Here, it would seem, several things are separately attended to at
once. The several things are similar, and close together, and the
responses required are all simple and much alike. Such responses,
under such very favorable conditions, are perhaps, then, not
inconsistent with each other, so that two, three, or even four such
attentive responses may be made at the same time.

(2) The _law of advantage_ holds good, as illustrated by the fact that
some distractions are harder to resist than others.

(3) The _law of shifting_ holds good, as illustrated by the constant
movement of attention, even when it is "sustained", and by the
alternation between two activities when we are trying to carry them
both along simultaneously.

(4) The _law of sustained attention_, or of _tendency_ in attention,
is the same old law of tendency that has shown itself repeatedly in
earlier chapters. A tendency, when aroused to activity, facilitates
responses that are in its line and inhibits others. A tendency is thus
a strong factor of advantage, and it limits the shifting of attention.

(5) A new law has come to light, the _law of combination_, which reads
as follows: _a single response may be made to two or more stimuli_;
or, _two or more stimuli may arouse a single joint response_.

Even though, in accordance with the law of selection, only one
attentive response is made at the same time, more than {264} one
stimulus may be dealt with by this single attentive response. Groups
of four dots are grasped as units, familiar