Hienz R D, Aleszczyk C M, May B J
University School of Medicine, Baltimore, Maryland 21205, USA.
J Acoust Soc Am. 1996 Aug;100(2 Pt 1):1052-8. doi: 10.1121/1.416291.
The ability of cats to discriminate changes in the second formant of the vowel /epsilon/ was examined across a range of stimulus levels. Cats were trained to press and hold down a lever to produce a pulsed train of the standard vowel /epsilon/, and to release the lever only when a variant of [epsilon] occurred. Six synthetic variants of /epsilon/ had the same first and third formants (F1 and F3), but with the second formant (F2) located between 1700 and 2000 Hz. All stimuli were tested at levels of 10, 30, 50, and 70 dB SPL. Average difference thresholds for changes in F2 (delta F2) of the vowel /epsilon/ ranged from 87 to 36 Hz across levels of 10 to 70 dB SPL, and were only slightly above those of humans. Further, the delta F2 values were lower than pure-tone delta F values in the same frequency range, whereas humans exhibit higher delta F2 values than pure-tone delta F values in the same frequency range. Changes in the second formant in a negative direction (downward F2 shifts) were also found to be more difficult to detect than upward F2 shifts. These results suggest that, compared to pure tones, cats are better able to discriminate small changes in more complex, vowel-like stimuli.
在一系列刺激水平下，研究了猫辨别元音/epsilon/第二共振峰变化的能力。训练猫按下并按住杠杆以产生标准元音/epsilon/的脉冲序列，并且仅在出现[epsilon]的变体时才松开杠杆。/epsilon/的六个合成变体具有相同的第一和第三共振峰（F1和F3），但第二共振峰（F2）位于1700至2000赫兹之间。所有刺激均在10、30、50和70分贝声压级下进行测试。在10至70分贝声压级范围内，元音/epsilon/的F2变化（ΔF2）的平均差异阈值在87至36赫兹之间，仅略高于人类的阈值。此外，在相同频率范围内，ΔF2值低于纯音ΔF值，而在相同频率范围内，人类的ΔF2值高于纯音ΔF值。还发现第二共振峰向负方向的变化（F2向下移动）比F2向上移动更难检测。这些结果表明，与纯音相比，猫在辨别更复杂的、类似元音的刺激中的微小变化方面表现更好。
