Visual Fixations, Attentional Detection, and Syntactic Perspective an Experimental Investigation of the Theoretical Foundations of Russel S. Tomlin's Fish Film Design

In the so-called fish film-experiment designed by the linguist Russell S. Tomlin it is tested whether the assignment of grammatical subject in on-line descriptive discourse production can be controlled by controlling the visual attentional detection of participants in a scene. It is an implicit assumption in the fish film framework that the point of optical focus is a good indicator of focal attention, and that attentional control can thus be gained by making test subjects look at a cued participant. This assumption has not previously been put to the test. In the present paper it is tested by comparing verbal fish film data with visual fixation data from children and adults. This reveals that there is actually no tight correspondence between visual fixations and subject assignment, contrary to what would be expected. It is considered whether an apparent error in the fish film itself can be held responsible for this lacking correspondence. While the error compromises the control of visual fixations, it is still possible to analyze the visual and verbal data for correspondences. Furthermore, it is found that a more traditional interpretation of the data in terms of information structure can be substituted for Tomlin's eye-language correspondence hypothesis in explaining the previous success of the fish film. It is concluded that Tomlin's hypothesis is not directly falsified by the pilot experiment, rather neutralized so that it may still, but not necessarily, be true. 1. I NT RO D U C T I ON In 1995 the linguist Russell S. Tomlin devised an experiment that was to become influential in the field of experimental psycholinguistics, the sub-field of linguistics that takes an empirical-experimental approach to the description of linguistic structure in the minds of speakers and hearers (Tomlin 1995). This experiment, known as the fish film, was designed to test the hypothesis that the grammatical choice of sentence subject in English is a linguistic manifestation of attentional focus and can thus be predicted given that focal attention is controlled. The fish film methodology has been used on many occasions to show that there is indeed a convincing correspondence between the entity in focal attention and grammatical subject, but on closer scrutiny the foundations of the fish film seem to have some minor flaws. In particular one seemingly basic theoretical assumption that is never really made explicit in Tomlin's writings on the effects of attention in language is interesting: that attentional focus presupposes visual focus (Tomlin 1984, 1986, 1995, and 1997; Tomlin and Villa 1994). It is possible to criticize Tomlin's cognitively grounded view on functional discourse for not sufficiently taking into account the possibility that visual perception may at least in part be independent of focal attention. Questions about the visual mechanisms at the base of cognition are simply not addressed. In the present paper, the different mental focusing mechanisms that can be assumed to underly the fish film description task are discussed: visual fixations, attentional detection, and syntactic perspective. Then, different views on how these mechanisms interact will be reviewed. It turns out that these mechanisms are not necessarily connected in a one-to-one fashion, and this forms the theoretical basis for an empirical investigation of the fish film framework. In particular, it will be investigated whether a oneto-one correspondence between visual fixations and attentionally detected information exists or not. This will be accomplished by using an eye-tracker to monitor the eye-movements of test subjects during the fish film experiment. It will be revealed whether the last point of visual fixation before utterance onset is indeed the entity that becomes sentence subject in the ensuing utterance, as would be expected according to Tomlin. As it turns out, there seems to be an error in the fish film itself, which effectively neutralizes the conclusion reached by Tomlin: that the successful control of attention focus makes it possible to predict the assignment of syntactic subject. Even if the fish film is thus not suitable to provide valid evidence for the correspondence suggested by Tomlin, it is obviously very suitable to elicit active and passive sentence configurations in a predictable way. This means that Tomlin may still be right, but unfortunately the success of the fish film can also be explained using a more traditional discourse analysis approach. In an earlier paper (Diderichsen 2001) I have shown how the production of passive constructions in children as old as 7 years of age defies the kind of experimental control of 'visual attention' that can apparently be obtained when the fish film is used with adult subjects. I presented the view that the postulated correspondence between attention and language could still be theoretically defended even though the attempts to control 'visual attention' clearly failed. I further suggested that the development of attentionally determined discourse strategies involves the independent development of selective attention and grammatical means of discourse profiling. These insights can all be maintained under the assumption that the focus mechanisms of vision are independent of attention and language, at least at the level of individual visual fixations. Thus, in this paper it is argued that the focus mechanisms of vision should be considered a factor in on-line linguistic description of visual material that surely plays an important role, but is not necessarily either determining nor determined by any of these other two factors. 2. T HE OR ET IC A L BAC K G RO UND One of the most fundamental characteristics of cognition is the ability to focus on some phenomena at the expense of others. This is reflected in different disciplines as theoretical notions of importance such as a b o u t n e s s , topicality, re levance , salience, perspective, foregrounding, the figure-ground and given-new dichotomies, etc. All these terms have been brought to bear on the selectiveness of human information procesing, and their similarity is highlighted by the fact that they have all occasionally been replaced by a metaphor of focus and periphery (see, for instance, Chafe 1994). In this section descriptions of the three focusing systems under investigation, namely those of vision, attention, and language, will be reviewed, as well as Tomlin's and other's views on how they interact, providing the theoretical background for the pilot experiment described below.