## 5 Discussion  
One needs error rates for lateralization decisions made by using only the ITD information, only the ILD information, and both of these two pieces of information. However, it is not possible to provide either one of these cues alone. Even when one of them is made zero, as it is generally done in ITD/ILD trading studies [17], both of the cues are made available inevitably, because either zero-ITD or zero-ILD still bears a spatial information indicating zero azimuth when sound is delivered dichotically. To circumvent this issue, we did not test the subject's accuracy in judging the absolute lateralization of single sound stimuli, but preferred using pairs of successive sounds producing bidirectional shifts in perceived lateral position of the sound, and tested the subject's performance (or error rate) in identifying the shift direction. By this way, it was possible to change only one of the cues without the condition that the other one must be set to zero. This made also possible to assess the bidirectional shift sensitivity of the system around different azimuthal angles in the azimuth range of 0 and 30 degrees. The results of the present study regarding the judgments of the TO, LO, and TL shifts conform tothe results of a previous study conducted by [PERSON] [15], which compared the mismatch negativity outcomes with ITD-ILD deviant complex stimulations. In both studies, [PERSON] [15] and the present one, the responses of the participants are more in line with estimated perceived azimuth based on the generic HRTF in the TL cases than TO cases. Simultaneous presentation of the ITD and ILD cues to the participants resulted in increased SNR values in all of the four azimuthal cases. While utilization of either ITD or ILD cue by the hearing system is possible, it is the combination of these two pieces of information when they are simultaneously available that leads to more confident lateralization of acoustical sources [8; 38]. Based on the SNR values of the experiments it can be said that the participants mostly trust the ILD cue for lateralizing the sound sources around the midline, whereas they relied almost equally on both the ITD and ILD cues for relatively peripheral azimuths. Our experimental results (available in Table 2) are in agreement with the findings of [PERSON] [39] that suggested an increase in error rates for smaller azimuth with ITD-imposed sound stimuli and larger azimuth with ILD-imposed sound stimuli. The auditory system relies more on the most consistent cue in lateralizing sound sources [40] and this could provide an explanation for the azimuth-dependent of the cues. Our diversity combination model considers the ITD and ILD cues as independent and uncorrelated cues. Based on our model, the experimental SNR values should fit the SNR values estimated by the model, depending on the level of independence of these cues from each other. While additive combination shows that the ITD and ILD cues are independently encoding, super- or sub-additive combination shows an interaction/coupling between the mechanisms encoding these cues or the channels transmitting them toward the brain's cortex. The experimental results of the present study showed super-additivity of the cues for azimuth near the midline, additivity for 20\({}^{\circ}\), and sub-additivity for 30\({}^{\circ}\). This suggests a nonlinear combination of modality-specific influences as the multi-cue whole is greater than the sum of its uni-cue parts. The results of the other studies [40; 41] investigating the significance of ITD and ILD in sound lateralization, have demonstrated subadditivity of the ITD and ILD cues, which indicates an overlap between the neural mechanisms processing the two cues, rather than their independence in cue coding. An important observation of the present study is the decrease in SNR values accompanied by an increase in the bias values that occurred as a result of the increase in azimuth.