Suga 2000). These plasticity effects appear to have important differences,
depending on the specializations of particular regions (Sakai and Suga
2001). Based on such data, we hypothesize that the representations of
complex acoustic events, such as vocal communication signals, are also
mediated by experience. Thus, it may be that, at any one time, the representational system is “tuned” to a subset of conspecific vocalizations related
to relevant tasks and contexts consistent with individual experience in a
manner similar to that observed for synthetic stimuli (e.g., Kilgard and
Merzenich 1998; Kilgard et al. 2001). Under such conditions, uninformed
choices of natural vocalizations presented during an experiment may be
incongruous with the representational state. One must be aware of the
behavioral relevance associated with each vocalization and attempt to
match the functional significance (i.e., the induced plasticity) of specific
vocalizations to the experience of specific animals.
The behavioral relevance of different vocalizations is also shaped by evolutionary history, and this provides an additional source for constraints on
the representational system. However, these effects are not always intuitively obvious. For example, vocal-communication based recognition can
take many forms, depending on the species under consideration. One commonly observed form of recognition is between heterospecific and conspecific signals (i.e., species recognition). Among the midshipman, Porichthys
notatus, a species of nocturnally active fish, for example, females appear to
use male acoustic signals to localize prospective mates (McKibben and Bass
1998). The same is true for many anurans (Capranica 1965; see Feng and
Ratnam 2000) as well as birds and mammals (Searcy and Yasukawa 1996).
Based on such widespread observations, one general function of the perceptual system may be to differentiate between heterospecific and conspecific signals. However, in many cases, animals are able to make much finer
discriminations between conspecific signals, and to the extent that behaviorally relevant classifications are made on the basis of intraspecific acoustic
variation, species recognition can be expected as an indirect by-product of
an auditory system tuned to other information. This leads to the hypothesis that interspecies recognition is related to the structure of the ascending
auditory system. It may not be necessary to postulate any special mechanisms or “templates” to account for innate predispositions for recognition
of conspecific vocalizations (cf. Konishi 1978; Marler and Sherman 1983).
Perhaps the most dramatic and compelling evidence for this comes from
chick/quail chimera studies, where perceptual predispositions were associated with midbrain structures that could be transferred across species (Long
et al. 2001). Because auditory feature detectors have mostly been described
in forebrain pathways, for example in birds and primates, we propose the
hypothesis that intraspecies recognition is related in these species to
the structure of the forebrain auditory system. In Section 3, we develop
intraspecies recognition as a model for perceptual and cognitive mechanisms of vocal communication.
352
T.Q. Gentner and D. Margoliash
depending on the specializations of particular regions (Sakai and Suga
2001). Based on such data, we hypothesize that the representations of
complex acoustic events, such as vocal communication signals, are also
mediated by experience. Thus, it may be that, at any one time, the representational system is “tuned” to a subset of conspecific vocalizations related
to relevant tasks and contexts consistent with individual experience in a
manner similar to that observed for synthetic stimuli (e.g., Kilgard and
Merzenich 1998; Kilgard et al. 2001). Under such conditions, uninformed
choices of natural vocalizations presented during an experiment may be
incongruous with the representational state. One must be aware of the
behavioral relevance associated with each vocalization and attempt to
match the functional significance (i.e., the induced plasticity) of specific
vocalizations to the experience of specific animals.
The behavioral relevance of different vocalizations is also shaped by evolutionary history, and this provides an additional source for constraints on
the representational system. However, these effects are not always intuitively obvious. For example, vocal-communication based recognition can
take many forms, depending on the species under consideration. One commonly observed form of recognition is between heterospecific and conspecific signals (i.e., species recognition). Among the midshipman, Porichthys
notatus, a species of nocturnally active fish, for example, females appear to
use male acoustic signals to localize prospective mates (McKibben and Bass
1998). The same is true for many anurans (Capranica 1965; see Feng and
Ratnam 2000) as well as birds and mammals (Searcy and Yasukawa 1996).
Based on such widespread observations, one general function of the perceptual system may be to differentiate between heterospecific and conspecific signals. However, in many cases, animals are able to make much finer
discriminations between conspecific signals, and to the extent that behaviorally relevant classifications are made on the basis of intraspecific acoustic
variation, species recognition can be expected as an indirect by-product of
an auditory system tuned to other information. This leads to the hypothesis that interspecies recognition is related to the structure of the ascending
auditory system. It may not be necessary to postulate any special mechanisms or “templates” to account for innate predispositions for recognition
of conspecific vocalizations (cf. Konishi 1978; Marler and Sherman 1983).
Perhaps the most dramatic and compelling evidence for this comes from
chick/quail chimera studies, where perceptual predispositions were associated with midbrain structures that could be transferred across species (Long
et al. 2001). Because auditory feature detectors have mostly been described
in forebrain pathways, for example in birds and primates, we propose the
hypothesis that intraspecies recognition is related in these species to
the structure of the forebrain auditory system. In Section 3, we develop
intraspecies recognition as a model for perceptual and cognitive mechanisms of vocal communication.
352
T.Q. Gentner and D. Margoliash