regard.We usually imagine the experience of other species of auditory
events as primarily an extension of sensitivity rather than a fundamen-
tal difference in experience.We know,however,that the use of auditory
information may be radically different in different species,usually elic-
iting stereotyped behavior patterns rather than the flexible information
that we know from experience with language.The most unusual animal
auditory activity is perhaps that of echolocation by microchiropteran
bats,which appear to construct an analogue of our three-dimensional
visual world from auditory data (Grinnell 1995).Although dolphins are
also echolocators,there is no evidence of their using auditory informa-
tion in this way.This has not inhibited my speculations about the
dolphin’s world as constructed from echoes (Jerison 1986).I suggested
a dolphin multiple-ego psychology;too odd to say more here.Those who
are intrigued will have to dig up the reference.
For me,the most evocative example of differences among species in
perceptual worlds is distinction between the visual worlds of horses and
rabbits and of anthropoid primates,including people.In addition to the
fact that the primate world is colorful whereas that of horses and rabbits
is probably one of gray pastels,our primate world is a proscenium stage
on which events are played out in a narrowly but sharply focused central
area with a peripheral background that extends only to our sides.Horses
and rabbits live in the center of a domed sphere,with eyes in the back
of their heads,as it were.Their visual field covers a full 360 degrees.Can
you imagine their experience? There is no “behind one’s back”for these
animals.Their visual world cannot be as fine-grained as ours,since their
largely rod vision cannot provide the detailed edge discrimination that
we achieve with the pure cone fovea centralis.Nonprimate mammals do
not have foveae,and their visual worlds are probably more nearly like
those of the earliest mammals,which probably first evolved as nocturnal
species of only slightly modified reptiles.
Major regions of the mammalian brain are specialized for receiving
and analyzing visual information,other regions for auditory information,
others for tactile information,and so forth.These are specialized in turn.
Each hemisphere of the primate cerebral cortex has at least a dozen
visual areas that are specialized in a variety of ways,for example,for
responding differently to edges of objects,to their movement in differ-
ent directions,to color,to size,and so forth (Zeki 1993).Comparable
specialization for vision occurs in most mammalian brains,but are less
elaborate in nocturnal species that rely less on vision for navigating their
worlds.The same elaboration probably occurs for auditory information,
although that domain is yet to be analyzed as elaborately as the visual
system.In bats,which use auditory cues for navigation in ways compa-
rable with the use of vision in primates,much of the cerebrum is spe-
cialized as auditory cortex.In the human brain,language areas have been188 Harry Jerison