Sources of performance on theory of mind tasks in right hemisphere-damaged patients.

Patients with right hemisphere (RHD) or left hemisphere brain damage (LHD) were tested on Theory of Mind (ToM) tasks presented with visual aids that illustrated the relevant premises. As a measure of pragmatic ability, patients were also asked to judge replies in conversation that violated Gricean maxims. Both RHD and LHD patients performed well on the ToM tasks presented with visual aids, but RHD patients displayed difficulty when the same tasks were presented only verbally. In addition, RHD patients showed reduced sensitivity to pragmatic violations. These findings point to the role of right hemisphere structures in processing information relevant to conversations. They indicate that a crucial source of RHD patients' errors in ToM tasks may involve difficulties in utterance interpretation owing to impairments of visuospatial processing required for the representation of textual information.

Selective impairments of theory of mind in people with schizophrenia.

"Theory of mind" (ToM) means the ability to represent others' intentions, knowledge and beliefs and interpret them. Children with autism typically fail tasks aimed at assessing their understanding of false beliefs. These features of autism are strikingly similar to some negative features of schizophrenia. Mental abilities were studied in 35 schizophrenics (DSM-IV) and 17 normal controls. Subjects heard four ToM stories and simultaneously were shown cartoons depicting the action occurring in the stories. All stories involved false beliefs or deception. As for the current symptomatology, schizophrenics were divided according to Liddle's three-dimensional model (reality distortion, psychomotor poverty, disorganisation). Our results show significant differences between schizophrenics and normal controls in all ToM stories, with schizophrenic people performing worse than controls. In first-order stories (a false belief about the state of the world) significant differences were found among symptom dimensions, with the psychomotor poverty group performing worse than disorganisation subjects and reality distortion ones. As for second-order stories (a false belief about the belief of another character), the psychomotor poverty group performed worse than the other groups only in one of the four ToM stories. More research in separating ToM deficits from attention disturbances is needed.

Do 9-month-olds perceive causation-at-a-distance?

Humans understand mechanical events to involve physical bodies interacting by contact, but intentional events involve agents that can also interact at a distance. We investigated infant sensitivity to causality in a simple event in which one agent appears to react to another without contact. Infants 9 months old were habituated to one of two events involving a computer-animated red square moving nonrigidly--like a caterpillar--towards a green square. In the 'reaction event', the green object moved in turn before the red one stopped, while in the 'pause event' the green object moved after the red one stopped. After habituation, each infant saw the habituation movie played in reverse. This test involved identical spatiotemporal changes for reaction and pause event, but the reversed reaction additionally involved a change in the causal roles. Infants dishabituated to reversal of the reaction but not the pause event, a result which suggests sensitivity to causation-at-a-distance. This ability could support development of social cognition and theory of mind.

Are children with autism deaf to gricean maxims?

Department of Psychology, Birkbeck College, University of London, UK High-functioning children with autism show a severe deficit in the development of pragmatics whereas their knowledge of syntax and morphology is relatively intact. In this study we investigated further their selective communication impairment by comparing them with children with specific language impairment (SLI) and normally developing children. We used a pragmatic task that involved the detection of utterances that violate conversational maxims (avoid redundancy, be informative, truthful, relevant, and polite). Most children with autism performed at chance on this task, whereas all children with SLI and all normal controls performed above chance. In addition, the success of children with autism on the pragmatics task was related to their ability to attribute false beliefs. These results are consistent with the idea that communication deficits in autism result from a selective impairment in representing propositional attitudes. Their implications for domain-specific views of cognitive development are discussed.

Children's ambiguous utterances: a re-examination of processing limitations on production.

The ability to convey the optimal amount of information during conversation is a fundamental aspect of language use. In this study the relationship between children's failures to produce unambiguous utterances and the mental effort demands of the communication task was investigated. Five-, six-, seven- and nine-year-old children performed a message production task and a finger-tapping task both separately and simultaneously. The decrease in finger-tapping frequency during the simultaneous performance was used as an estimate of effort demands of the message production task. Working memory capacity was assessed by means of a spatial memory test and an object features identification task. Children's intuitions about message adequacy were recorded in two message evaluation tasks. By age six children proved to be able to select the relevant information when they were explicitly asked to do so, indicating that effort demands of the communication task did not exceed their computational resources. However, results suggested that the relative effort requirements of the communication task decrease with increasing age. These findings support a performance theory of communication development in which effort demands are a determinant of children's message adequacy.

Concreteness effects in free recall: the roles of imaginal and relational processing.

Two experiments reevaluated the possible role of mental imagery in free recall of concrete and abstract words. In Experiment 1, the number and rate of list presentations were manipulated. Incidental recall following an imagery rating task yielded reliable concreteness effects after two presentations but not after a single presentation, regardless of presentation rate. In Experiment 2, we examined the effects of relational (categorization) and item-specific (imagery rating) processing tasks on memory for categorically related or unrelated concrete and abstract words. Concreteness effects were obtained when unrelated words were sorted into categories but not when they were rated on imagery. Related words failed to yield concreteness effects under any orienting condition. The results support the view that the presence or absence of concreteness effects in free recall depends on the relative salience of distinctive and relational information. This conclusion constrains theoretical explanations of the role of mental imagery in memory and cognition.

Do children exploit the Maxim of Antecedent in order to interpret ambiguous descriptions?

Twenty Italian six-year-olds and 20 eight-year-olds were asked to interpret eight ambiguous and eight clear definite descriptions. All ambiguous descriptions could refer to three drawings, one of which had been described by the subjects immediately before the comprehension task. In half of the trials with ambiguous messages the children's interlocutor was present while the children were describing the drawings; in the other half he was absent. In both conditions subjects showed a preference for the referents they had already described, indicating that they applied egocentrically a comprehension strategy based on the Maxim of Antecedent (Jackson & Jacobs, 1982). Children's failures to differentiate their responses in the two conditions are considered to be due to difficulties in taking account of the given-new distinction for relevant information.