Fig 1.
Schema of Deutsch’s scale illusion.
(a) The stimulus is constructed from two diatonic major scales, one ascending and the other descending. (b) Through earphones, the melody patterns most subjects experience hearing while listening to (a). Few subjects perceive a full ascending or descending scale, which are shown in (c).
Fig 2.
Schema of Deutsch’s scale illusion drawn as a line graph.
This figure is equivalent to Fig 1a and 1b and is shown here for easier comparison with other note patterns. Stimulus (R), which is shown by the red circles and solid line, represents the notes presented to the right ear. Stimulus (L), which is shown by the blue Xs and dotted line, represents the notes presented to left ear. The orange solid line and the green dotted line show the percept coming from the right and the left ears, respectively.
Fig 3.
Dichotic tone patterns for Experiment 1a.
An ascending scale was presented alternately to the right and left ear. Stimulus (R) and Stimulus (L) show the tone patterns presented to the right and left ear, respectively. When a tone from the scale was presented to the right ear, the pitch of the tones presented to the left ear was one of the following: (a) two whole tones lower (2TL), (b) one whole tone lower (1TL), (c) equal (0T), or (d) one whole tone higher (1TH) than that presented to the right ear.
Fig 4.
Mean ratios of perception of the ascending scale in Experiment 1a.
The graph shows the mean ratio of the ascending scale that was perceived more clearly when compared with the other tone patterns. *: p < 0.05. **: p < 0.05 against all other tone patterns.
Fig 5.
Dichotic tone patterns showing the counterpart notes.
Images showing an additional line graph (green dotted line) in Fig 3. The notes that are connected with the green line are counterparts of the ascending scale that are presented alternately from opposite ears.
Fig 6.
Additional tone patterns for Experiment 1b.
Tonal sequence 1TH was replaced with (e), which is named CN. The additional green dotted line drawn on the right graph shows the counterparts of the ascending scale that are presented alternately to the opposite ears.
Fig 7.
Mean ratios of perception of the ascending scale in Experiment 1b.
The graph shows that the mean ratio of the ascending scale was perceived more clearly when compared with the other tone patterns. There were no statistically significant differences among the groups.
Fig 8.
Passages of "Lightly Row" used for Experiments 2a and 2b.
The graphs show 7 versions of the tone patterns constructed for these studies. (a) is a diotic version that plays the melody for both ears identically (DO). (b) is a version of the dichotic tonal sequence that plays the melody alternately to the right ear and left ear (2TL). (c) and (d) are versions in which only the tone patterns of the right or left channel of 2TL are heard diotically and were named 2TLR and 2TLL, respectively. Similarly, (e) is another dichotic version (CN), (f) is a right channel version (CNR), and (g) is a left channel version (CNL).
Fig 9.
Passages of "Cherry Blossoms" and "Jingle Bells" used for Experiment 2a and 2b.
(b) and (e) show the 2TL version and CN version of "Cherry Blossoms" and "Jingle Bells".
Fig 10.
Means ratios of the correct song answers.
For all three passages, many of the subjects answered correctly when they heard DO. When they heard 2TL or CN, correct titles were also provided by many subjects. When they heard 2TLR, 2TLL, CNR, and CNL, fewer subjects answered correctly for the titles "Cherry Blossoms" and "Jingle Bells," but for "Lightly Row," more subjects answered correctly when they heard these versions. Statistical analyses were performed with comparison to DO. *: p < 0.05.
Fig 11.
Mean ratios of melodies perceived clearly when compared to other versions.
The results were almost identical regardless of the passage. Compared to ratio of the dichotic versions 2TL and CN, the ratio was lower when "jagged" tone patterns were heard diotically (2TLR, 2TLL, CNR, and CNL). The ratio of version 2TL was lower than that of DO when subjects heard the "Lightly Row" or "Jingle Bells" passage. In the case of "Cherry Blossoms," the ratio of 2TL was not statistically different from that of DO. There were no statistically significant differences between the ratios for DO and CN for all three passages. In the graphs, the results of Experiment 2a are drawn as a reference (dotted bars). *: p < 0.05. ns: not significant.