DISCRIMINATORY APPROACH TO AUDITORY STIMULI IN GUINEA FOWL (NUMIDA MELEAGRIS) AFTER HYPERSTRIATAL∕HIPPOCAMP- AL BRAIN DAMAGE

238

Fig. 5. For three groups of Guinea fowl this diagram shows the frequency of occurrence
of search (S), low tension (LT) and high tension (HT) (vertical axis) in successive 5-s
periods (horizontal axis) for 1 min after a food-trill. For further details see legend for Fig.

that within this range there was no discernible effect of sound pressure levels.
The attenuation of frequency in the filter-trills (T_{1 2 3}) had little effect. Most
birds approached at first. The number of cycles per second in the stimulus
was more important. The faster trills were more likely to elicit approach than
slower trills or rhythms.

For the filter-trills and the ‘novel’ stimulus group (T_{4 7 8}) the anterior and
sham-control groups spent a similar period by the dish that was less than half
that for the posterior group. The third stimulus group (T_{2 6 9}) elicited mixed
responses. To the slow trill (T₂) both lesion groups approached more than
controls. All three groups approached the ‘arousal’-trill (T₆) for a fairly long
period. Only one bird from each lesion group and no control approached the
iambus call (T₉).

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