Developmental differences in the control of action selection by social information

Our everyday actions are often performed in the context of a social interaction. We previously showed that, in adults, selecting an action on the basis of either social or symbolic cues was associated with activations in the fronto-parietal cognitive control network, whereas the presence and use of social versus symbolic cues was in addition associated with activations in the temporal and medial prefrontal cortex (MPFC) social brain network. Here we investigated developmental changes in these two networks. Fourteen adults (21–30 years of age) and 14 adolescents (11–16 years) followed instructions to move objects in a set of shelves. Interpretation of the instructions was conditional on the point of view of a visible “director” or the meaning of a symbolic cue (Director Present vs. Director Absent) and the number of potential referent objects in the shelves (3-object vs. 1-object). 3-object trials elicited increased fronto-parietal and temporal activations, with greater left lateral prefrontal cortex and parietal activations in adults than adolescents. Social versus symbolic information led to activations in superior dorsal MPFC, precuneus, and along the superior/middle temporal sulci. Both dorsal MPFC and left temporal clusters exhibited a Director × Object interaction, with greater activation when participants needed to consider the directors' viewpoints. This effect differed with age in dorsal MPFC. Adolescents showed greater activation whenever social information was present, whereas adults showed greater activation only when the directors' viewpoints were relevant to task performance. This study thus shows developmental differences in domain-general and domain-specific PFC activations associated with action selection in a social interaction context

Children's mental representation of referential relations : representational partitioning and "theory of mind"

In six experiments I investigated children’s handling of intensional contexts. The results were described in terms of a developmental extension of Fauconnier’s mental spaces account of meaning representation. Implications for children’s mentalistic development were explored. In chapter 1 I considered the “referential opacity” raised by the representational nature of the mind. I interpreted the findings of Russell (1987) as evidence for a developmental dissociation between handling of intensional contexts - due to the partial nature of representations - and “intentional” referential problems - due to representations being outdated or hypothetical. In experiments 1-3 I demonstrated this dissociation explicitly, and showed that it extended to non-linguistic intensional contexts. Experiments 4 &5 showed correlations between children’s handling of intensional contexts and linguistic ambiguity, which I explained by their common requirement that representational content be held as partial. Experiment 6 showed that children’s handling of intensional questions (and mentalistic explanations) improved after observing incorrect action on the basis of partial knowledge. This effect of supporting context was short-lived, suggesting that it supported on-line activity not question comprehension. After earlier success with out-dated and hypothetical representations, children’s handling of partial representations at 6-7 years explains their concurrent late success with intensional contexts and linguistic ambiguity, and constitutes a qualitative change in their representational abilities

Can one written word mean many things? Prereaders’ assumptions about the stability of written words’ meanings

Results of three experiments confirmed previous findings that in a moving word task, prereaders 3 to 5 years of age judge as if the meaning of a written word changes when it moves from a matching to a nonmatching toy (e.g., when the word “dog” moves from a dog to a boat). We explore under what circumstances children make such errors, we identify new conditions under which children were more likely correctly to treat written words’ meanings as stable: when the word was placed alongside a nonmatching toy without having been alongside a matching toy previously, when two words were moved from a matching toy to a nonmatching toy, and when children were asked to change what the print said. Under these conditions, children more frequently assumed that physical forms had stable meanings as they do with other forms of external representation

Using perspective to resolve reference: the impact of cognitive load and motivation

Research has demonstrated a link between perspective-taking and working memory. Here we used eye-tracking to examine the time course with which working memory load (WML) influences perspective-taking ability in a referential communication task, and how motivation to take another’s perspective modulates these effects.  In Experiment 1, where there was no reward or time-pressure, listeners only showed evidence of incorporating perspective knowledge during integration of the target object, but did not anticipate reference to this Common Ground object during the pre-target noun period. WML did not affect this perspective use. In Experiment 2 - where a reward for speed and accuracy was applied - listeners used perspective cues to disambiguate the target object from the competitor object from the earliest moments of processing (i.e. during the pre-target noun period)- but only under low load. Under high load, responses were comparable with the control condition, where both objects were in common ground. Furthermore, attempts to initiate perspective-relevant responses under high load led to impaired recall on the concurrent WML task, indicating that perspective-relevant responses were drawing on limited cognitive resources. These results show that when there is ambiguity, perspective cues guide rapid referential interpretation when there is sufficient motivation and sufficient cognitive resources

Current knowledge on the role of the inferior frontal gyrus in Theory of Mind - a commentary on Schurz and Tholen (2016)

Schurz and Tholen (2016) argue that common approaches to studying the neural basis of “theory of mind” (ToM) obscure a potentially important role for inferior frontal gyrus (IFG) in managing conflict between perspectives, and urge new work to address this question: “to gain a full understanding of the IFG's role in ToM, we encourage future imaging studies to use a wider range of control conditions.” (p332). We wholeheartedly agree, but note that this observation has been made before, and has already led to a programme of work that provides evidence from fMRI, EEG, and TMS on the role of IFG in managing conflict between self and other perspectives in ToM. We highlight these works, and in particular we demonstrate how careful manipulation within ToM tasks has been used to act as an internal control condition, wherein conflict has been manipulated within-subject. We further add to the discussion by framing key questions that remain regarding IFG in the context of these. Using limitations in the existing research, we outline how best researchers can proceed with the challenge set by Schurz and Tholen (2016)

The relationship between proliferation and differentiation during oligodendrocyte development

How do precursor cells know when it is time to stop dividing and differentiate? The phenomenon of lineage-specific progenitor cells undergoing a limited period of proliferation prior to terminal differentiation is a common theme in multicellular development. Despite this, little is understood about how these two events are co-ordinated during the normal schedule of development. I have studied the question of how proliferation and differentiation are co-regulated in the oligodendrocyte lineage in the rodent optic nerve. Oligodendrocytes are post-mitotic cells that myelinate axons in the vertebrate central nervous system. They develop from precursor cells whose maturation is controlled by a timer, which is an intrinsic property of the cells, that limits proliferation. The timer seems not to control the number of divisions the cell can undergo but rather the length of time during which divisions can occur. Significant effort has been devoted to understanding how the intracellular timer regulates oligodendrocyte development. The timer consists of two components that are modulated by distinct kinds of extracellular signals. Mitogens drive a timing component whose value increases as precursor cells continue to divide. Once this value exceeds a critical threshold, it signals that the proliferative period has elapsed, and hydrophobic signalling molecules trigger an effector component that elicits cell-cycle arrest and differentiation. The value of the timing component is determined by several intracellular molecules whose activities change as the timer runs. One of these molecules is the cell-cycle inhibitor p27: it accumulates in oligodendrocyte precursor cells as they proliferate in culture. When p27 expression is high the precursor cells are more likely to stop dividing and differentiate than when it is low. In oligodendrocyte precursor cells derived from mice that lack p27, the timer runs aberrantly and cell-cycle arrest and terminal differentiation are delayed. It is not understood how the molecular mechanics of the timer control oligodendrocyte development. Does the timer serve to arrest the cell-cycle, with differentiation following by default, or is cell-cycle arrest subordinate to the programme of terminal differentiation? These questions remain unanswered, largely because of a persistent inability to experimentally manipulate the genome of oligodendrocyte precursor cells. The present study was an attempt to overcome these problems and had two aims - first, to devise a reliable system for transfecting oligodendrocyte precursor cells and second, to determine whether the timer primarily controls the timing of cell-cycle arrest. I developed a new retroviral vector that co-expresses p27 and green fluorescent protein (GFP) in precursor cells. The use of GFP allows the identification of living precursor cells that over-express p27, which can then be followed over many days in culture. My findings support previous work showing that p27 plays a role in governing the timing of oligodendrocyte differentiation. They show that over-expression of p27 promotes oligodendrocyte differentiation by advancing the value of the timing component, although it does not promote differentiation if the effector component is inoperative. The cell-cycle time of precursor cells that over-express p27 is dramatically extended, but not stopped. It appears that a firm cell-cycle arrest and entry into a quiescent state may be required to elicit terminal differentiation

Human-centred explanations for artificial intelligence systems

As Artificial Intelligence (AI) systems increase in capability, so there are growing concerns over the ways in which the recommendations they provide can affect people's everyday life and decisions. The field of Explainable AI (XAI) aims to address such concerns but there is often a neglect of the human in this process. We present a formal definition of human-centred XAI and illustrate the application of this formalism to the design of a user interface. The user interface supports users in indicating their preferences relevant to a situation and to compare their preferences with those of a computer recommendation system. A user trial is conducted to evaluate the resulting user interface. From the user trial, we believe that users are able to appreciate how their preferences can influence computer recommendations, and how these might contrast with the preferences used by the computer. We provide guidelines of implementing human-centred XAI.</p