VIOLENCIA FAMILIAR:

Research on intersensory processing has been weakly supported since the pioneering work of Todd (1912; cited in Gregory, 1987). His general finding was that reaction to a stimulus reduces when that stimulus is accompanied by an accessory. The response is usually given to a visual stimulus, while the accessory is non-informative implying that the subject need not attend to it in order to execute the RT task. Numerous hypotheses have been suggested to account for these results.

Historically the oldest one is the energy-summation hypothesis. It suggests that energy from the accessory combines in some way with the energy from the imperative stimulus, leading to more processing in the earlier stages and hence to earlier arrival times. In this account, no suggestion of the nature of the processes underlying this combination of energy, or indeed how it speeds reaction time, is presented. For this reason the energy summation account is no longer taken seriously. Others have explained the results by highlighting inadequacies in the methodologies of these experiments. Apparently, the earliest findings were based on paradigms without catch trials; catch trials being a situation where the accessory was presented on its own and the subjects were instructed to withhold their response. Though Nickerson (1973) and Posner (1978) cited a preference for designs which included catch trials, their inclusion remained problematic for two reasons.

Firstly, Nickerson (1973) comments that RT to vision alone when such trials are embedded within a series of other kinds of trials (e.g. catch trials and vision and accessory trials) is usually inflated somewhat reflecting the old idea that RT is not so much a function of the particular stimulus that was presented, but of that stimulus in relation to other possible stimulus events. A second difficulty is that subjects have reported using different strategies in experiments

with and without catch trials. In accounting for the speeded intersensory responses, Raab (1962) has argued that "the facilitation of RT is based on the subject using that modality, which for a particular trial happens to provide the earliest indication that some stimulus was presented" (see Gielen, 1983, p. 162). However, Gielen et al. (1983) demonstrated that even by using a modified paradigm to correct for Raab's "statistical facilitation hypothesis", some form of intersensory facilitation, yielding faster RT, was still occurring. They hypothesised "that if the combined imperative-plus-accessory RT can be shown to be shorter than the reaction to the imperative stimulus alone, with corrections for statistical facilitation using a modification of Raab's procedures then a stronger basis for "true" intersensory facilitation of RT would be provided" (p. 166). Their results showed that for every subject," the response to the combined stimulus events were more rapid than could be predicted by the statistical facilitation model" ( p. 166).

Ittyerah and Broota (1983) have suggested that the speeded reaction times do not result from intersensory processing but depend on the amount of practice that each modality has in executing that task. For example they suggests that " haptic perception is not intrinsically fragile though it appears to be so due to the inexperience of sighted subjects on haptic tasks" (p.508). In a series of experiments using all combinations of tactile and visual sets, Itterah found that all conditions which involved the visual modality were faster. This, she interpreted as evidence in support of her hypothesis, since sighted subjects often utilise the visual modality for most transactions with the environment.

To date, the riddle of intersensory facilitation remains unresolved. Bernstein (1973) and Nickerson (1973) have argued in favour of a preparation-

enhancement model. Here, the accessory stimulus is assumed to provide an "alerting" or arousing role on the many stages of processing, so that the affected stages are terminated more quickly and the response comes earlier. Posner (1978) in agreement with the preparation enhancement model suggests a more specific alerting hypothesis; in this view, the accessory stimulus causes the subject to respond earlier to the build up of information in a stage involving stimulus identification. Posner's view differs from the preparation enhancement view of Nickerson in that the locus of the effect seems limited to stimulus identification, whereas it can be located in any of a number of later stages in Nickerson's view (See Schmidt et al. 1984 for review).

In more recent research the trend seems to be directed toward looking at the processes being activated when a subject is engaged in visual reaction time tasks. Letourneau at si. (1986) attributed the benefit to visual reaction when preceded with an auditory accessory as due to changes in the subject's level of alertness. In agreement with Posner (1978) they" explain the phenomenon of visual dominance on the assumption that visual inputs have a weaker capacity than auditory inputs to alert the organism" (p. 671). Sanders (1990) suggests that an auditory stimulus of a certain intensity level (75 dB) produces a short cut activation of the motor adjustment process. However, Keuss at si. (1990) found that visual reactions were faster with increasing intensity of the auditory stimulus. This decrement amounted to 15 msec for an intensity range of 40 to 80 dB; above 80 dB, a decrement in performance was cited for a choice reaction time paradigm though simple RT tasks continued to benefit. In conclusion, these study suggest that an auditory accessory facilitates motor reactions, due to some activating or alerting mechanism which short cuts motor processes and thereby reduces response times. This is the most recent account of why an auditory accessory speeds reaction to a visual stimulus.

Since this time the direction of research on intersensory processing has changed course and more recent papers have been concerned with cross modal matching ability. Squire et al. (1993) examined cross modal matching ability ("the ability to identify a stimulus in one sensory modality on the basis of information presented in a different modality" (p.375) in amnesiac patients . ^ Their results indicated that severe memory impairment could occur without disrupting cross modal performance.

Other concurrent work has focused on the anatomical locus of cross modal associations. Salazar et al. (1993) conducted a study with rats in which cross modal transfer was examined following visual and auditory cortical ablations. Cross modal transfer of information was unaffected by the ablation and Salazar et al. concluded that some sub-cortical structures (such as the amygdala , superior colliculus or reticular formation) might be responsible for the transfer of information cross modally. However the work of Nahm et al.

(1993^ with neurological patients has dismissed that the amygdala is the site of cross modal processing in humans. So far, agreement on the locus of multi-sensory and cross modal processing has not been reached. Until the nature of cross modal processing in normal individuals is more fully understood it will be difficult to localise the precise area of anatomical involvement.

In the present study what is important is whether valid cueing will lead to faster reaction times in the cross modal as well as in the within-modality conditions and whether the modality of cue produces any variance. So far only one such study has addressed this issue. Buchtel and Butter (1988) examined the effects of spatial cues on the speed of reaction to target stimuli in the same and different modalities using a modification of Posner's paradigm. The relevant details of this study will be elaborated given its similarity to the

present project. Their study consisted of two experiments. The first compared the effect of visual and auditory spatial cues on reaction time to visual stimuli; the second compared the effect of the same spatial cues on reaction times to auditory stimuli. In their experiments the visual cue consisted of four red light emitting diodes (LEDs), arranged in a square pattern around each of the visual targets. The auditory cue provided was a burst of white noise from two small loud speakers located behind the visual stimuli. The results from experiment one confirmed their hypothesis that a non-visuospatial cue, in this case an auditory cue, could be as effective as a visuospatial cue in shifting attention.

However, the results were not quite as appealing in the second experiment where the exact same cues were used but the target was substituted with an auditory target. Here their finding was that the same visual and auditory cues that led to costs and benefits when the target was visual were totally ineffective when the target was replaced with an auditory one. Buchtel and Butter interpret these findings to mean that visual stimuli, unlike auditory stimuli, evoke orienting head and eye movements that improve stimulus identification because the foveal region of the retina can be brought to bear on stimuli needing fine analysis.

According to this view, when the task requires responses to visual targets, as in experiment one, attention will shift covertly irrespective of the cue modality, because the cues are linked to a system that controls orienting movements for improving identification to the target stimulus; with auditory targets, no covert orienting would be evoked by the same visual and auditory cues effective in experiment one, because there was no orienting movements of the auditory system that serves to improve identification of auditory stimuli. However Posner (1980) suggests in his studies using visual cues and visual targets that orienting to cued and uncued locations in visual space occurs

independently of eye and head movements. Secondly, Buchtel and Butter used various cue to target onset intervals, ranging from 50 - 1000 msecs.

According to Posner the benefit and cost of valid and invalid cueing is more pronounced when the cue to target onset interval is between 50 -150 msecs.

Buchtel and Butter failed to consider this, and did not analyse the main effects of cue separately for all the various intervals.

A somewhat interesting effect in both these experiments is that the validity effect of auditory cues was consistently larger than those of visual cues. Buchtel and Butter explain this effect as being due to a difference in the intensity or salience of the cue rather than a genuine modality difference in the attentional properties of the two cues. Another finding specific to experiment one was that reaction times associated with the auditory cues were faster than those associated with the visual cues. This they commented resulted either because auditory cues have a greater alerting effect than visual cues or alternatively they suggested that the finding might reflect a reaction time advantage when the cue modality differs from the target stimulus.

It will be interesting to see if the results of this present project support the findings of Buchtel and Butter. Though the general hypothesis and paradigm employed are quite similar, the methodology and cue and target type are different. Catch trials are not employed in this experiment unlike that of Buchtel and Butter, as previous research on intersensory facilitation has suggested that subjects use different response strategies in trials involving catch trials and in those without (Nickerson, 1973). Also, unlike the objectives of the present project, Buchtel and Butter were interested to see whether the field of presentation of the cue or the cue to target onset interval introduced any variation in their findings. The present study concentrates more specifically on how the modality of the cue and target interact and whether the

congruence of the cue is influential in all cases of the cue/target combinations.

The final section addresses issues concerning the practical value and theoretical implications of this kind of research.