1.2. Base teórica
1.2.2. El derecho ambiental internacional
The present study was designed to address two empirical questions; (1) Is the auditory modality capable of covert shifts of attention in a manner similar to that of the visual modality?
(2) What is the nature of cross modal processing when the task demands attention to be unified across modalities?
For convenience each of these issues will be considered separately. Since experiment two was conducted primarily as a control study, and a contrast between the results of both experiments has already been presented, reference will only be made to experiment one in considering these issues unless the results of experiment two are directly relevant.
Consistent with previous research in this area a significant main effect of valid in preference to invalid cueing resulted. This was true of all conditions and occurred independently of whether the cue was a visual or an auditory one. Unlike the findings of Buchtel et al. (1988) this would seem to suggest that the auditory modality is as responsive to valid spatial cueing as the visual modality (refer to Table 1). However the effect of miscuing (as in trials with an invalid cue) was far more pronounced in the auditory modality than in the visual modality. This suggests that when the cue was valid the auditory modality is just as efficient at shifting attention covertly; but when the cue misdirects attention, the act of disengaging attention from the present focus and moving to an alternative location is a more effortful task for the auditory modality This was especially noticeable in conditions involving an auditory target, and seems to occur irrespective of whether the cue was visual or auditory one, (refer to Table 1; compare conditions VAv' & 'VAi' and 'AAv' & 'AAi'). While these
findings tend to support the proposition that there are independent mechanisms for the control of attention in both of these modalities, the results are really insufficient to draw any firm conclusion. However if one is to argue for the alternative hypothesis and assume that the covert shifting of attention is a general function of a less specialised attentional system rather than an unique property of specific modalities, then one would hardly expect any differences between any conditions at all. This is clearly not the finding of the present study and only further investigation will help to clarify the issues.
When the nature of spatial orienting across modalities is addressed a rather intriguing result emerges (refer to conditions 'VAv', 'VAi', 'AVv' and 'AVi', Table 1). Though an overall beneficial effect of valid over invalid cueing was maintained, the speed of response was highly sensitive to the nature of the cue and target type involved (i.e. visual or auditory). Circumstances seem optimal when the cue is an auditory one and the target is a visual one. This of statistically significant: visual targets yielded significantly faster reaction times than did auditory targets and trials involving auditory cues were significantly faster than those involving visual cues. This effect is neatly reversed by switching the order and type of cue and target such that conditions involving a visual cue and an auditory target now yield the slowest response. This is true even when compared with the within modality conditions and remains constant despite changes to the congruence of the cue. This is a very surprising result. If one agrees with the proposition that visual targets are faster because the visual modality is more practised in these sort of tasks than other modalities, then why are visual cues not as fast as other types of cue trials? Similarly, if auditory cues are faster then why do the same principles not apply when the target is auditory? It would be premature to believe that a single property of either modality could be solely responsible for this effect. Instead it seems that the relationship of the cue and target type to other cognitive systems might
need to be explored further.
One might speculate, for example, that when the spatial relevance of cue is dictated via the semantic content of a word, it is likely that the visual and auditory system utilise different (though not necessarily separate) access procedures to this information. At present there is no research to substantiate this claim, but one possible suggestion for the present study might be to change the nature of how the spatial information is presented, while keeping all other variables constant. One option might be to present a semantically irrelevant word in a spatial location which could either be valid or invalid and compare the results with the findings of the present study. This is the choice for the next experiment. The exact experimental specifications will be discussed in the method section of experiment 3. It will be interesting to see whether any alteration in the nature of the cue will make a difference to the pattern of results already obtained.
2.5.1 SUMMARY
In conclusion the results of this study would seem to suggest that there may indeed be independent mechanisms for the control of attention in the visual and auditory modalities. However, the results are insufficient to draw any firm conclusions. When considering the nature of cross modal processing it appears that the cue and target type produce different effects within both modalities. It has been suggested that the nature of the cue type might be responsible and this is being investigated in the next experiment. Only further investigation will shed more light on this issue.