was Professor of Biological Psychology in this department (undergraduate and postgraduate studies). Her interests are in sensory psychophysiology, psychophysics, and assessment of quality of life. John Orley trained as both an anthropologist and as a physician (with a specialist qualification in psychiatry). Currently Programme Manager of the WHO Mental Health Program, Geneva, his recent work centered on mental health promotion, including work on quality of life, the psychosocial development of infants, children, and adolescents, and improving the communication and behavioral skills of health workers. Shekhar Saxena, a member of the Royal College of Psychiatrists, had his basic medical and psychiatry training at the All-

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Reaction times (RTs) to four groups of substances that provoke different taste qualities were measured. Measurements for all substances with the same taste, equalized in perceived intensity and provoking a very strong taste, were made concurrently for each subject. The comparisons were made on the individual level. No significant differences in RTs to substances with the same taste quality were found. When the factor of perceived intensity is kept constant, no effect of the stimulus chemical composition on RTs seems to be present. RTs to stimuli with different tastes differ significantly, the shortest being to salt and the longest to bitter. The difference in RTs for sour and sweet substances is small, and the subjects were not all alike in terms of the order of RTs with respect to these stimuli.Although by far the dominant part of total reaction time (RT) is attributable to the time of cortical processing events (Halpern, 1986), some significant differences in RTs to various taste substances imply that the time of receptor-organ events can also playa detectable role. In fact, some investigators, on the basis of their gustatory RT results, have made certain remarks concerning the similarity or dissimilarity in the receptor transduction process. But these RT comparisons have been limited to various salt and sweet substances (yamamoto, Kato, Matsuo, Kawamura, & Yoshida, 1985;Yamamoto & Kawamura, 1984) or to a few stimuli that evoke a sour taste (Bujas, Szabo, Mayer, Ajdukovic, & Vodanovic, 1989). Also, in some of these studies, the different subjects have been stimulated by different substances, so that a great intervariability could have distorted the comparison results.The purpose of the present study was to obtain, if possible, some information on the receptor transduction mechanism by comparing RTs to various typical substances with the same taste quality, with the same subjects being exposed to all the stimuli used. Because the taste RT for a substance varies widely with its taste intensity, it was necessary, within each group of substances and for each individual subject, to equalize perceived taste intensities carefully. To diminish the influence of each subject's intravariability from session to session, all RT Correspondence may be sent to Silvija Szabo, Department of Psychology, Filozofski fakultet, University of Zagreb, Dj. Salaja 3,41000 Zagreb, Yugoslavia. measurements for substances with the same taste quality were made concurrently. Moreover, to have a common reference point, the RTs to l.OM NaCl in all sessions were determined. METHOD Apparatus and StimuliTaste stimuli were applied to the anterior part of the tongue by a gravity flow system. To assure an initially uniform hydrodynamic pressure of the liquid against the tongue surface, a siphon container was used. From this container, the solution flowed through three channels at 6 ml/sec over a tongue area of about 7 em', eliciting, at contact, only a slight touch sensation. The stimulus duration time was 5 sec. The solutions were warmed to 38°C.Fo...

In spite of a clear increment in absolute thresholds as an effect of self-adaptation, the electrically provoked taste sensation does not show a reduction in subjective intensity during the protracted stimulation time. Chemical cross-adaptation effects on the threshold and suprathreshold levels of electrical taste are observed only when the adapting solutions are electrolytes regardless of their taste qualities. It seems that the stability of perceived intensity during current flow is principally due to some irritation of the sensitive tissue of the tongue, whereas cross-adaptation effects may be attributed to the potential changes across the excitable membranes caused by electrical properties of adapting electrolytic solutions.In one of the first studies concerning electrical taste, Volta (1792) observed that the electrically provoked taste sensation lasted all the time during the current flow and that in the course of that period taste intensity went up.In opposition to the well-known gustatory adaptation phenomena, does this statement indicate that the sensory structures that are the site of adaptation changes are bypassed in the electrical stimulation of the tongue?The purpose of this investigation was to check the correctness of Volta's observation and to collect some data on the influence of the protracted stimulus action time and on cross-adaptation effects on evoked electrical taste. GENERAL METHODElectrical taste was evoked by means of anodal or cathodal direct current. An electrical stimulator and nonpolarizable Ag:AgO electrodes dipped in 0.1% NaO were used. The stimulation was monopolar. The contact between the active electrode and the tongue was made by a plug of agar with a surface of about 60 mm' . The indifferent electrode was a bath for [mgers of the left hand with a contact surface of about 50 em'. The electrodes were in series with a resistance of 30K ohms or greater. To avoid transients at the onset of direct current stimulation, a special device was used to obtain a rapid but smooth onset of the stimulus.In the experiments with cross adaptation, the taste solutions were applied by means of a flow system through a glass stimulator. The solution· flowed over a limited surface of the tongue (1.8 cm') with a speed of 15 cm 3 /sec. Four trained Os took part in the experiments. EXPERIMENT I: PERCEIVED INTENSITY OF ELECTRICAL TASTE BEFORE, AT THE END OF, AND AFTER ADAPTATIONThe Os were instructed to estimate the overall subjective intensity of electrical stimuli. The perceived intensity was evaluated by the Stevens (1969) procedure of direct magnitude estimation, with the standard set equal to 10. The standard was given before each stimulus was to be evaluated. In experiments with the anode, the standard was 70 microA and the stimulation lasted 3 sec. For cathodal stimulation the standard was 200 microA and the duration was 4 sec.Five adapting current intensities were applied in each of the two kinds of electrical stimulation. The adaptation time was 20 sec. Three seconds before the end of the adapt...