1994). Apparently, amusic individuals have failed to acquire this implicit knowledge ... the selectivity of the musical pitch-based disorder in congenital amusia, by.
Congenital Amusia: Impaired Musical Pitch But Intact Musical Time
KRISTA L. HYDE, and ISABELLE PERETZ Department ofPsychology, University of Montreal, Montreal, Quebec, Canada
1.
INTRODUCTION
The existence of a developmental disorder of music, colloquially known as 'tone-deafness', has been entertained for over one century (Grant-Allen, 1878; Geschwind, 1984). However, it is only recently that a large research effort has been made to study the origins of such a disorder, currently termed 'congenital amusia' (Ayotte et al, 2002; Peretz et al, 2002; Hyde and Peretz, 2003; Peretz and Hyde, 2003). Afflicted individuals have a severe, life-long impairment in both the perception and production of music, which cannot be explained by obvious sensory or brain anomalies, low intelligence or lack of environmental stimulation to music. The disorder appears to be limited to the musical domain, and spares language. Congenital amusics process and recognize speech, including speech prosody, common environmental sounds and human voices as well as control subjects (Ayotte e/a/., 2002). Collective findings show that congenital amusics have a deficit that affects the processing of musical pitch, while musical time perception seems much less affected (Ayotte et al, 2002). Most notably, afflicted individuals have a severe problem in the detection of anomalous pitches inserted in popular melodies (Ayotte et al., 2002; Kalmus and Fry, 1980). The pitch anomalies consist of tones that do not belong to the key in which the melody has been written and hence sound incongruous in the melodic context, for listeners of Western music. Even young listeners with no formal musical 291
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training are quite sensitive to these key violations (Trainor and Trehub, 1994). Apparently, amusic individuals have failed to acquire this implicit knowledge about the pitch structure of the surrounding music. As mentioned, the deficit seems to be specific to the pitch dimension of music since discrimination of musical rhythms has been shown to be intact in about half of the congenital amusic individuals studied to date (Peretz et ai, 2003). However, this relative sparing of time processing has not yet been assessed in music perception. Prior studies have involved a "samedifferent" discrimination task that is quite demanding in terms of memory (Ayotte et ai, 2002). Therefore, the goal of the present study was to assess the selectivity of the musical pitch-based disorder in congenital amusia, by using perceptual tasks that involve the detection of a musical anomaly either in time or in pitch, while maintaining a constant musical context. Tablet. Characteristics of participants, mean percentages of correct responses on subtests of the Montreal Battery of Evaluation of Amusia (MBEA), and significance levels on corresponding t tests. Standard deviations are in parentheses.
Characteristics Age (yrs) Gender Education (yrs) Musical discrimination Melodic (MBEA) Rhythmic (MBEA)
2.
Amusic (n=10) 58 (6.3) 3M,7F 16(1.5)
Control (n=10) 58 (6.4) 3M,7F 16(1.3)
t- test n.s.
61.0(6.8) 74.3(13.2)
91.4(9.4) 92.1 (8.2)
P
