Psychology Assignment 1

as well as hypertrophy. Because Burmese pythons naturally undergo a 40%, fully reversible increase in ventricular mass in the two days after a meal, they could provide an attractive model for investigating the funda- mental mechanisms that lead to cardiac remodelling and ventricular growth9. The physiological stimuli underlying this hyper- trophy are still unknown, but are likely to include neural and humoral factors. Johnnie B. Andersen*, Bryan C. Rourke†, Vincent J. Caiozzo‡, Albert F. Bennett*, James W. Hicks* Departments of *Ecology and Evolutionary Biology, and ‡Orthopaedics, University of California, Irvine, California 92697, USA e-mail: [email protected] †Department of Biological Sciences, California State University, Long Beach, California 90840, USA 1. Cooper, G. Annu. Rev. Physiol. 49, 501–518 (1987).

2. Richey, P. A. & Brown, S. P. J. Sports Sci. 16, 129–141 (1998).

3. Secor, S. M. & Diamond, J. Nature 395, 659–662 (1998).

4. Secor, S. M. & Diamond, J. Am. J. Physiol. 272, R902–R912

(1997).

5. Starck, J. M. & Beese, K. J. Exp. Biol. 204, 325–335 (2001).

6. Vliegen, H. W., Bruschke, A. V. G. & Van Der Laarse, A. Comp.

Biochem. Physiol. A: Physiol. 95, 109–114 (1990).

7. Secor, S. M., Hicks, J. W. & Bennett, A. F. J. Exp. Biol. 203,

2447–2454 (2000).

8. Morgan, H. E. et al. Annu. Rev. Physiol. 49, 533–543 (1987).

9. Quinn, K. E. et al. Biophys. J. 74, A355 (1998).

Supplementary information accompanies this communication on

Nature’s website.

Competing financial interests: declared none.

Synaesthesia

When coloured sounds taste sweet

Synaesthesia is the involuntary physical experience of a cross-modal linkage — for example, hearing a tone (the induc-

ing stimulus) evokes an additional sensation of seeing a colour (concurrent perception). Of the different types of synaesthesia, most

have colour as the concurrent perception1, with concurrent perceptions of smell or taste being rare2,3. Here we describe the case of a musician who experiences different tastes in response to hearing different musi- cal tone intervals, and who makes use of her synaesthetic sensations in the complex task of tone-interval identification. To our knowledge, this combination of inducing stimulus and concurrent perception has not been described before.

E.S. is a 27-year-old professional musi- cian who is female,right-handed and of aver- age intelligence4 (IQ, 115). Whenever she hears a specific musical interval, she auto- matically experiences a taste on her tongue that is consistently linked to that particular interval (Table 1). Besides this exceptional interval-to-taste synaesthesia,she also reports the more common tone-to-colour synaes- thesia, in which each particular tone is linked to a specific colour (for example, C and red; F sharp and violet).

Both synaesthetic perceptions have always been consistently reproducible. We repeatedly tested E.S. for over a year and have confirmed that her interval-to-taste synaes- thesia is unidirectional: she does not hear tone intervals when exposed to taste.In addi- tion, E.S. applies this synaesthesia in identi- fying tone intervals (which is evidence of a synaesthesia–cognition cascade).

To assess the influence of E.S.’s synaes- thetic gustatory perception on her ability to identify tone intervals, we adapted the Stroop task5 (for methods, see supplemen- tary information). Four selected tone inter- vals (seconds and thirds) were presented while applying four differently tasting solu- tions (sour, bitter, salty and sweet) to E.S.’s tongue. Her task was to identify the tone intervals by pressing a particular button for each interval on a computer keyboard. Reac- tion times and errors were measured for trials in which the applied taste was either congruent or incongruent with the tone interval; tone intervals were also presented without taste stimulation.

We found that E.S.’s tone-interval identi- fication was perfect and was significantly faster during the congruent condition com- pared with all the other conditions (Fig. 1). Five non-synaesthetic musicians were tested as controls using the same procedure: no sig- nificant between-condition differences were found. The reaction times of the controls were comparable to those of E.S. in the no-taste condition (Fig.1).

To exclude conceptual priming effects as an explanation for these results (for example, the subject might imagine sourness when presented with ‘sour’ as either a taste or word), we also tested E.S. by showing her the word(s) describing each taste. We found no between-condition difference in this conceptual task (Fig.1).

Together, these results indicate that E.S.’s

performance in the gustatory Stroop task is most likely to be due to her extraordinary type of synaesthesia, in which a complex inducing stimulus leads to a systematic, concurrent gustatory sensation. This case differs from another gustatory synaesthete,S., who reported blended gustatory sensations (such as specific meals) in response to simple auditory stimuli (tones and sounds)2. E.S.’s application of her synaesthetic sensations in identifying tone intervals — a complex task that requires formal musical training — demonstrates that synaesthesias may be used to solve cognitive problems. Gian Beeli, Michaela Esslen, Lutz Jäncke Institute of Neuropsychology, University of Zurich, 8032 Zürich, Switzerland e-mail: [email protected] 1. Rich, A. N. & Mattingley, J. B. Nature Rev. Neurosci. 3, 43–52

(2002).

2. Luria, A. R. The Mind of a Mnemonist (Basic Books, New York,

1969).

3. Ward, J. & Simner, J. Cognition 89, 237–261 (2003).

4. Horn, W. Leistungsprüfsystem (Hogrefe, Göttingen and Bern,

1983).

5. Stroop, J. R. J. Exp. Psychol. 18, 643–662 (1935).

Supplementary information accompanies this communication on

Nature’s website.

Competing financial interests: declared none.

brief communications

38 NATURE | VOL 434 | 3 MARCH 2005 | www.nature.com/nature

0

200

400

600

800

1,000

Taste Conceptual Taste

E.S. Controls

** *** *

R ea

ct io

n tim

e (m

s)

Figure 1 Mean reaction times in a gustatory Stroop task linking

perception of tone intervals with different tastes for congruent-

taste (grey), incongruent-taste (red) and no-taste (blue) condi-

tions for synaesthete E.S. and for five non-synaesthetic

musicians (controls). In the ‘Taste’ condition, musical intervals

were presented while solutions of different taste (citric acid,

20 g litre–1; quinine, 60 mg litre–1; salt, 10 g litre–1; sucrose,

120 g litre–1) were delivered to the subject’s tongue. The

‘Conceptual’ condition followed the same procedure, except that

words describing the tastes, instead of the tastes themselves,

were visually presented 2 s before the tone interval. Non-para-

metric randomization tests were used for statistical comparison.

For E.S., all statistical comparisons in the taste condition were

associated with P values of less than 0.01 (*P�0.05,

**P�0.01, ***P�0.001). For control subjects and for the con-

ceptual condition, none of the comparisons revealed significant

differences. The reaction time of E.S. in the no-taste condition is

similar to those of the controls, but is faster in the congruent

condition and slower in the incongruent condition.

Table 1 Tastes triggered by tone intervals

Tone interval Taste experienced

Minor second Sour

Major second Bitter

Minor third Salty

Major third Sweet

Fourth (Mown grass)

Tritone (Disgust)

Fifth Pure water

Minor sixth Cream

Major sixth Low-fat cream

Minor seventh Bitter

Major seventh Sour

Octave No taste

Tastes experienced by synaesthete E.S. in response to different musical tone intervals are shown; in the case of the fourth and tritone intervals, however, complex visual and emotional perceptions, respectively, are induced. Note that dissonant tone intervals induce unpleasant tastes and consonant ones induce pleasant ones (for example, the minor second intervals induce sour tastes, and the major thirds induce sweet ones). There is also an apparent symmetry in some of the responses: the minor second and major seventh, which are mirror-image intervals in terms of octave equivalence, are both rated as sour, and the major second and minor seventh are both rated as bitter.

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