Haem-responsive gene transporter enables mobilization of host haem in ticks.

Ticks, notorious blood-feeders and disease-vectors, have lost a part of their genetic complement encoding haem biosynthetic enzymes and are, therefore, dependent on the acquisition and distribution of host haem. Solute carrier protein SLC48A1, aka haem-responsive gene 1 protein (HRG1), has been implicated in haem transport, regulating the availability of intracellular haem. HRG1 transporter has been identified in both free-living and parasitic organisms ranging from unicellular kinetoplastids, nematodes, up to vertebrates. However, an HRG1 homologue in the arthropod lineage has not yet been identified. We have identified a single HRG1 homologue in the midgut transcriptome of the tick Ixodes ricinus, denoted as IrHRG, and have elucidated its role as a haem transporter. Data from haem biosynthesis-deficient yeast growth assays, systemic RNA interference and the evaluation of gallium protoporphyrin IX-mediated toxicity through tick membrane feeding clearly show that IrHRG is the bona fide tetrapyrrole transporter. We argue that during evolution, ticks profited from retaining a functional hrg1 gene in the genome because its protein product facilitates host haem escort from intracellularly digested haemoglobin, rendering haem bioavailable for a haem-dependent network of enzymes.

Development of theory of mind and executive control.

Several recent studies have demonstrated a developmental link, in the age range of 3-5 years, between the acquisition of a 'theory of mind' and self control. In this review, we consider the existence of such a link in assessing five competing theoretical hypotheses that might help us to understand the nature of this developmental advance: (1) executive control depends on theory of mind; (2) theory of mind development depends on executive control; (3) the relevant theory of mind tasks require executive control; (4) both kinds of task require the same kind of embedded conditional reasoning; (5) theory of mind and executive control involve the same brain region. We briefly describe these theoretical accounts and evaluate them in the light of existing empirical evidence. At present, only account (3) can be ruled out with some confidence.

The Effects of Framing, Reflection, Probability, and Payoff on Risk Preference in Choice Tasks.

A meta-analysis of Asian-disease-like studies is presented to identify the factors which determine risk preference. First the confoundings between probability levels, payoffs, and framing conditions are clarified in a task analysis. Then the role of framing, reflection, probability, type, and size of payoff is evaluated in a meta-analysis. It is shown that bidirectional framing effects exist for gains and for losses. Presenting outcomes as gains tends to induce risk aversion, while presenting outcomes as losses tends to induce risk seeking. Risk preference is also shown to depend on the size of the payoffs, on the probability levels, and on the type of good at stake (money/property vs human lives). In general, higher payoffs lead to increasing risk aversion. Higher probabilities lead to increasing risk aversion for gains and to increasing risk seeking for losses. These findings are confirmed by a subsequent empirical test. Shortcomings of existing formal theories, such as prospect theory, cumulative prospect theory, venture theory, and Markowitz's utility theory, are identified. It is shown that it is not probabilities or payoffs, but the framing condition, which explains most variance. These findings are interpreted as showing that no linear combination of formally relevant predictors is sufficient to capture the essence of the framing phenomenon. Copyright 1999 Academic Press.

A theory of implicit and explicit knowledge.

The implicit-explicit distinction is applied to knowledge representations. Knowledge is taken to be an attitude towards a proposition which is true. The proposition itself predicates a property to some entity. A number of ways in which knowledge can be implicit or explicit emerge. If a higher aspect is known explicitly then each lower one must also be known explicitly. This partial hierarchy reduces the number of ways in which knowledge can be explicit. In the most important type of implicit knowledge, representations merely reflect the property of objects or events without predicating them of any particular entity. The clearest cases of explicit knowledge of a fact are representations of one's own attitude of knowing that fact. These distinctions are discussed in their relationship to similar distinctions such as procedural-declarative, conscious-unconscious, verbalizable-nonverbalizable, direct-indirect tests, and automatic-voluntary control. This is followed by an outline of how these distinctions can be used to integrate and relate the often divergent uses of the implicit-explicit distinction in different research areas. We illustrate this for visual perception, memory, cognitive development, and artificial grammar learning.

Older (but not younger) siblings facilitate false belief understanding.

Results from 4 experiments and an analysis in which all data from 444 English and Japanese children are pooled show (a) a linear increase in understanding false belief with the number of older siblings, (b) no such effect for children younger than 3 years 2 months, (c) no helpful effect of younger siblings at any age (despite the large sample), (d) no effect of siblings' gender, and (e) no helpful effect of siblings on a task measuring children's understanding of how they know something. Discussion involves speculation about how older siblings may assist children (e.g., through pretend play and mental state language) and how different aspects of a theory of mind may develop through different means.

The many faces of belief: reflections on Fodor's and the child's theory of mind.

I contrast Fodor's theory of the child's Very Simple Theory of Mind (VSTM), which differs from adult folk psychology only in that it recognizes fewer intentional objects, with my view that children's concepts cross-cut the adult conceptual system. More specifically, young children do not distinguish between the state of affairs a belief is about and how this state of affairs is though of, which puts a severe limit on their understanding of belief as distinct from pretence. The two different positions are evaluated against empirical data on children's developing "theory of mind".

Episodic memory and autonoetic consciousness: developmental evidence and a theory of childhood amnesia.

This research draws together Tulving's (1985) view on episodic memory and research on children's developing "theory of mind." Episodic memory, in its technical meaning given by Tulving, requires the autonoetic consciousness of having experienced remembered events, but developmental findings suggest that children cannot encode events as experienced before the age of about 4 or 5 years. Before this age they have insufficient understanding of what constitutes experience, specifically they do not reflect on the perceptual origin of their own knowledge. To demonstrate such a link children between 3 and 6 years were assessed for their understanding of the perceptual origin of their own knowledge on different "see-know tests," in particular a test assessing understanding that our senses inform only about certain aspects of the perceived objects. A significant association was found between passing see-know tests and free recall, which persisted even when cued recall and verbal intelligence are partialed out. These results are used to argue that between 3 to 6 years children develop the ability to remember events as experienced and that this development can explain adults' inability to have recollective experiences of childhood events before that age (childhood amnesia).

Reflecting on scientific thinking: children's understanding of the hypothesis-evidence relation.

3 experiments were carried out to examine children's understanding of the role of covariation evidence in hypothesis formation. Previous research suggested that it is not until 8 to 11 years of age that children begin to understand how a given pattern of covariation supports a particular hypothesis about which factor is causally responsible for an observed effect. Experiments 1 to 3 employed a different (fake evidence) technique than previous research and showed that by 6 years of age most children understand how evidence would lead a story character to form a different hypothesis than the subject's own. Experiment 3 showed that most 6- and young 7-year-olds understand how a character's future actions (e.g., choice of an object) and predictions of future outcomes depend on the hypothesis he or she holds.

Does the autistic child have a metarepresentational deficit?

This study examines the claim that autistic children lack a "theory of mind" because of an inability to metarepresent. We argue that if autistic children have a "metarepresentational" deficit in Leslie's (1987, 1988) sense of the term, then they should have difficulty not only with mental representations such as false beliefs, but also with external representations such as photographs. Autistic children's understanding of photographic representations was tested using Zaitchik's (1990) task. This task is modelled on the false belief task (Baron-Cohen, Leslie, & Frith, 1985; Wimmer & Perner, 1983) but involves "false" photographs where a photographic representation does not conform with the current state of the real world. Like Zaitchik (1990) we found that normal 3 and 4-year-olds found this task as difficult as the false belief task. In sharp contrast, however, the autistic children in our study passed the photograph task but failed the false belief task. As both tasks require the ability to decouple, this evidence challenges the view that autistic children lack "metarepresentational" ability in Leslie's sense. However, the results leave open the question of whether autistic children have a metarepresentational ability in the different sense of the term intended by Pylyshyn (1978), that is, representing the relationship between a representation and what it represents.

Understanding the mind as an active information processor: do young children have a "copy theory of mind"?

Most 4-, but no 3-year-olds, were able to understand the mind's active role in evaluating the truth of verbal information. They appreciated that a statement, whether true or false, will be disbelieved if the listener has existing beliefs to the contrary and that it will be believed if no such beliefs exist. Four- and 5-year-olds were equally competent in understanding the need for interpretation of pictorial material. They realized that an uninitiated person cannot make sense of a "droodle", which in itself is an uninterpretable section of a larger meaningful drawing. We discuss the impact of our findings on the question of whether children at this age entertain a copy theory of mind.

Exploration of the autistic child's theory of mind: knowledge, belief, and communication.

26 autistic children with mental ages of 3-13 years were tested on 3 tasks that are within the capability of 3- or 4-year-old normal children. The first task tested understanding of a mistaken belief. Children were shown a typical box of a certain brand of sweets, and they all thought that it contained that kind of sweet. To their surprise, however, the box contained something else. Yet, only 4 out of the 26 autistic children were able to anticipate that another child in the same situation would make the same mistake. In contrast, all but 1 of 12 children with specific language impairment, matched for mental age, understood that others would be as misled as they had been themselves. The autistic children were also tested for their ability to infer knowledge about the content of a container from having or not having looked inside. All 4 children who had passed the belief task and an additional 4 performed perfectly, but most failed. The third task assessed children's pragmatic ability to adjust their answers to provide new rather than repeat old information. Here, too, most autistic children seemed unable to reliably make the correct adjustment. These results confirm the hypothesis that autistic children have profound difficulty in taking account of mental states.

Developmental differences in encoding length series.

Children ages 6-13 and college students had to remember length relationships for 3 pairs of sticks. In one task, 4 sticks (A, B, C, D) were used and the training pairs were interlinked, i.e., A greater than B, B greater than C, C greater than D. In another task, 6 sticks were used to form 3 unrelated pairs, i.e., A greater than B, C greater than D, E greater than F. For 6-7-year-olds interlinked pairs were much more difficult to retain than unrelated pairs, whereas the opposite held true for college students. As a check on the stability of this finding, the linguistic form of questions and the number of different lengths of sticks were varied, but the same results were obtained. It is suggested that the previously observed difficulty that children encounter in learning length series in comparison to adults is not only due to a lack of motivation or attention or memory limitation but also to a difference in approach to the task.