Research at MACCS
Research at MACCS focuses on the production and comprehension of normal and disordered spoken and written language (see the Language Program), the processing of visual information (see the Visual Cognition Program) and the modelling of the nature of delusions in schizophrenia and other disorders including e.g. Capgras, Cotard, Fregoli, and Mirror delusions (see the Belief Formation Program).
Language
The ultimate aim of this project is to build a complete computational model of all aspects of language processing at the single-word level. That is, the model should offer an explanation of how people recognize spoken words, produce speech, read, and spell, and how they understand the spoken or written word. It should also offer explanations of specific disorders of language processing that occur after brain damage - specific impairments of the ability to produce spoken language, to recognize spoken language, to read, or to write, and also specific difficulties in understanding language, as seen for example in Alzheimer's Disease.
The starting point of this project is an existing computational model of visual word recognition and reading aloud, the DRC (Dual Route Cascaded) model (Coltheart, Curtis, Atkins & Haller, 1993; Coltheart & Rastle, 1994; Rastle & Coltheart, 1999a, 1999b).
Belief
Our work in this domain has focussed on delusional belief, hallucination, and the nature of the theory of mind impairment in schizophrenia. The major achievement so far has been the development of a two-factor theory of delusional belief. According to this theory, the various types of delusional belief all arise because of the joint presence of two cognitive abnormalities. The first is an aberration of perception or emotion which gives rise initially to the belief in question. This belief ought to be rejected because it is usually bizarre or implausible and because the deluded person's family, friends and clinicians all insist that it is false. It is because of a second cognitive abnormality, defective operation of a belief evaluation system, that the deluded person accepts the delusional belief as true. We have successfully applied this theory to a variety of delusions such as Capgras delusion (the belief that someone emotionally close to you, typically your spouse, has been replaced by an identical-looking impostor), mirrored-self misidentification (the belief that the person you see when you look in the mirror is not you, but some stranger who looks like you) and anosognosia for hemiplegia (the belief that your left limbs are not paralysed when in fact they are, because of right hemisphere damage). Our work here provides a theoretical basis for the use of cognitive-behavioural therapy for the treatment of delusion and hallucination in psychosis.
Visual Cognition
This research aims to provide a greater understanding of how visual information is processed. Some of our research is focused on how people obtain information from visual stimuli, such as words or letters, pictures of objects, actions or scenes when they are presented very briefly (~100ms). These short presentation times enable the investigation of what information is processed quickly and what information is lost. Many of our experiments use rapid serial visual presentation (RSVP), where stimuli are presented sequentially in the same spatial location for a brief time. Masked priming is another experimental paradigm that is used at MACCS.
Another research focus is how people process information about faces and emotions. Recently, this has involved studying people with prosopagnosia (a selective difficulty in recognising familiar faces) and temporal lobe epilepsy (disrupted brain activity in the temporal lobe which is important for recognising facial expressions).
Some research in the Belief Formation project overlaps with the Visual Cognition project, for example, the pattern of eye movements shown by people with schizophrenia when they are looking at photographs of faces is abnormal: the facial regions most informative about the emotion being expressed by the face (the eyes, mouth and nose) are not fixated, as they are by normal observers, and we believe that this is one the factors leading to the impairments of social cognition seen in people with schizophrenia.
We also conduct research into synaesthesia, a condition which involves a 'mixing of the senses'. In synaesthesia, stimulation in one sense gives rise to an additional perceptual experience (e.g., seeing a particular colour evokes the sound of a musical note). Synaesthesia allows us to examine unique questions about visual cognition and the processes in the brain that lead to conscious experience. There are many different forms of synaesthesia. Click here to find out more about synaesthesia and our research.