This homework examines the perception of the acoustic dimension of "voice onset time" (VOT), a dimension that is relevant for the representation of stop voicing contrasts in English and many other languages. The stimuli that we will use are from the Auditory Demonstration Tapes, prepared in 1978 at the Laboratory of Psychophysics, Harvard University, under National Science Foundation Grant SED76-24215.

These stimuli were synthesized using a series formant synthesizer, using 3 formants. The formant transitions cue a dorso-velar stop followed by steady formants for a low back vowel. The only in which the stimuli differ is in the VOT value, which ranges from 10 ms to 80 ms in 10-ms steps (so: 10 ms, 20ms, 30ms, 40ms, 50ms, 60ms, 70ms, 80ms).

In the identification half of the experiment, you heard each stimulus 6 times. These 48 repetitions were randomized in 3 blocks of 16 each. The stimulus number you heard is given on the back of this sheet. There was a two-second separation between stimuli, with a tone separating the blocks.

In the discrimination half of the experiment, you heard four repetitions of twelve stimuli triples. The first two stimuli in each pair differed in VOT by 20 ms; half of the pairs had shorter VOT stimuli first while the other half had longer VOT stimuli first. The last stimulus in the triplet matched either the first or the second stimulus. In other words, the triplets included the following:

1-3-1 1-3-3 2-4-2 2-4-4 3-5-3 3-5-5 4-6-4 4-6-6 5-7-5 5-7-7 6-8-6 6-8-8

3-1-1 3-1-3 4-2-2 4-2-4 5-3-3 5-3-5 6-4-4 6-4-6 7-5-5 7-5-7 8-6-6 8-6-8

In this half of the experiment, a tone separated each stimuli triplet while a triple tone separated blocks of triplets.

Your task is to graph your own results for both the identification and the discrimination tasks. For your identification graph, calculate the number of times you chose each category as the response for each of the 8 stimuli; for your discrimination graph, calculate how many times you correctly responded for each of the stimuli triplets. Plot the stimulus number or initial stimuli pair on the x-axis and response percentage on the y-axis. (You may sort stimuli triplets by order of presentation, if you so desire.) You may do this by hand or on computer.

In a few sentences, discuss your graphs. Have your responses adhered to the categorical perception model?

Identification

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1. ka ga

2. ka ga

3. ka ga

4. ka ga

5. ka ga

6. ka ga

7. ka ga

8. ka ga

9. ka ga

10. ka ga

11. ka ga

12. ka ga

13. ka ga

14. ka ga

15. ka ga

16. ka ga

-----------------------------

17. ka ga

18. ka ga

19. ka ga

20. ka ga

21. ka ga

22. ka ga

23. ka ga

24. ka ga

25. ka ga

26. ka ga

27. ka ga

28. ka ga

29. ka ga

30. ka ga

31. ka ga

32. ka ga

-----------------------------

33. ka ga

34. ka ga

35. ka ga

36. ka ga

37. ka ga

38. ka ga

39. ka ga

40. ka ga

41. ka ga

42. ka ga

43. ka ga

44. ka ga

45. ka ga

46. ka ga

47. ka ga

48. ka ga

Discrimination

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1. A B

2. A B

3. A B

4. A B

5. A B

6. A B

7. A B

8. A B

9. A B

10. A B

11. A B

12. A B

-----------------------------

13. A B

14. A B

15. A B

16. A B

17. A B

18. A B

19. A B

20. A B

21. A B

22. A B

23. A B

24. A B

-----------------------------

25. A B

26. A B

27. A B

28. A B

29. A B

30. A B

31. A B

32. A B

33. A B

34. A B

35. A B

36. A B

-----------------------------

37. A B

38. A B

39. A B

40. A B

41. A B

42. A B

43. A B

44. A B

45. A B

46. A B

47. A B

48. A B

Identification Key

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1. 1

2. 4

3. 7

4. 3

5. 6

6. 2

7. 5

8. 8

9. 7

10. 3

11. 1

12. 5

13. 2

14. 6

15. 8

16. 4

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17. 3

18. 6

19. 8

20. 4

21. 7

22. 1

23. 5

24. 2

25. 2

26. 4

27. 7

28. 5

29. 8

30. 1

31. 6

32. 3

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33. 4

34. 1

35. 6

36. 2

37. 5

38. 8

39. 3

40. 7

41. 7

42. 2

43. 8

44. 3

45. 5

46. 1

47. 4

48. 6

Discrimination Key

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1. 2-4-2

2. 8-6-6

3. 4-2-4

4. 1-3-1

5. 7-5-5

6. 6-8-6

7. 3-5-3

8. 6-4-4

9. 3-1-1

10. 5-3-5

11. 4-6-6

12. 5-7-7

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13. 5-3-3

14. 1-3-3

15. 4-6-6

16. 7-5-5

17. 8-6-6

18. 2-4-4

19. 6-4-6

20. 3-1-3

21. 6-8-8

22. 3-5-3

23. 5-7-5

24. 4-2-2

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25. 7-5-7

26. 2-4-4

27. 8-6-8

28. 5-3-5

29. 4-6-4

30. 1-3-3

31. 6-8-6

32. 4-2-4

33. 6-4-6

34. 5-7-5

35. 3-5-5

36. 3-1-1

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37. 6-4-4

38. 7-5-7

39. 1-3-1

40. 3-5-5

41. 5-3-3

42. 4-6-4

43. 5-7-7

44. 8-6-8

45. 2-4-2

46. 3-1-3

47. 4-2-2

48. 6-8-8