Theory of mind (ToM) has long been recognized to play a major role in children’s social functioning. However, no direct evidence confirms the causal linkage between the two. Here we addressed this significant gap by examining whether ToM causes the emergence of lying, an important social skill. We showed that after participating in ToM training to learn about mental state concepts, 3-year-olds who originally had been unable to lie began to deceive consistently. This training effect lasted for more than a month. In contrast, 3-year-olds who participated in control training to learn about physical concepts were significantly less inclined to lie than the ToM trained children. These findings provide the first experimental evidence supporting the causal role of ToM in the development of social competence in early childhood.

Deception is commonly seen in everyday social interactions. However, most of the knowledge about the underlying neural mechanism of deception comes from studies where participants were instructed when and how to lie. To study spontaneous deception, we designed a guessing game modeled after Greene and Paxton (2009), in which lying is the only way to achieve the performance level needed to end the game. We recorded neural responses during the game using near-infrared spectroscopy (NIRS). We found that when compared to truth-telling, spontaneous deception, like instructed deception, engenders greater involvement of such prefrontal regions as the left superior frontal gyrus. We also found that the correct-truth trials produced greater neural activities in the left middle frontal gyrus and right superior frontal gyrus than the incorrect-truth trials, suggesting the involvement of the reward system. Furthermore, the present study confirmed the feasibility of using NIRS to study spontaneous deception.

Elementary school children’s cheating behavior and its cognitive correlates were investigated using a guessing game. Children (N = 95) between 8 and 12 years of age were asked to guess which side of the screen a coin would appear on and received rewards based on their self-reported accuracy. Children’s cheating behavior was measured by examining whether children failed to adhere to the game rules by falsely reporting their accuracy. Children’s theory-of-mind understanding and executive functioning skills were also assessed. The majority of children cheated during the guessing game, and cheating behavior decreased with age. Children with better working memory and inhibitory control were less likely to cheat. However, among the cheaters, those with greater cognitive flexibility use more tactics while cheating. Results revealed the unique role that executive functioning plays in children’s cheating behavior: Like a double-edged sword, executive functioning can inhibit children’s cheating behavior on the one side, while it can promote the sophistication of children’s cheating tactics on the other.

An investigation on the feasibility of sputtering a diamond block into a specially designed three-dimensional cutting tool shape using a focused ion beam (FIB) was carried out. The ion-sputtered removal rate, surface morphology and sputtered feature accuracy were evaluated with respect to the FIB parameters such as ion current and angle of ion incidence through sputtering pockets on the top surface of a diamond substrate. A single crystalline diamond tool, with 25 µm length in the cutting edge and smooth face quality, has been successfully fabricated by using a FIB. These excellent tool characteristics are proven in the results obtained from the machining experiments done on the ultra-precision machine.

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The present study used the functional Near-infrared Spectroscopy (fNIRS) methodology to investigate the neural correlates of elementary school children’s own- and other-race face processing. An old-new paradigm was used to assess children’s recognition ability of own- and other-race faces. FNIRS data revealed that other-race faces elicited significantly greater [oxy-Hb] changes than own-race faces in the right middle frontal gyrus and inferior frontal gyrus regions (BA9) and the left cuneus (BA18). With increased age, the [oxy-Hb] activity differences between own- and other-race faces, or the neural other-race effect (NORE), underwent significant changes in these two cortical areas: at younger ages, the neural response to the other-race faces was modestly greater than that to the own-race faces, but with increased age, the neural response to the own-race faces became increasingly greater than that to the other-race faces. Moreover, these areas had strong regional functional connectivity with a swath of the cortical regions in terms of the neural other-race effect that also changed with increased age. We also found significant and positive correlations between the behavioral other-race effect (reaction time) and the neural other-race effect in the right middle frontal gyrus and inferior frontal gyrus regions (BA9). These results taken together suggest that children, like adults, devote different amounts of neural resources to processing own- and other-race faces, but the size and direction of the neural other-race effect and associated functional regional connectivity change with increased age.

Scientific research on how children learn to tell lies has existed for more than a century. Earlier studies mainly focused on moral, social, and situational factors contributing to the development of lying. Researchers have only begun to explore the cognitive correlations of children's lying in the last two decades. Cognitive theories suggest that theory of mind (ToM) and executive function (EF) should be closely related to the development of lying since lying is, in essence, ToM and EF in action. Yet, findings from empirical studies are mixed. To address this issue, the current meta‐analysis reviewed all prior literature that examined the relations between children's lying and ToM and/or between children's lying and EF. In total, 47 papers consisting of 5099 participants between 2 and 19 years of age were included, which yielded 74 effect sizes for ToM and 94 effect sizes for EF. Statistically significant but relatively small effects were found between children's lying and ToM (r = .17) and between lying and EF (r = .13). Furthermore, EF’s correlation with children's initial lies was significantly smaller than its correlation with children's ability to maintain lies. This comprehensive meta‐analysis provides a clear picture of the associations between children's ToM/EF and their lying behavior and confirms that ToM and EF indeed play a positive role in children's lying and its development.

The present study focused on the potential application of fNIRS in the detection of concealed information. Participants either committed a mock crime or not and then were presented with a randomized series of probes (crime-related information) and irrelevants (crime-irrelevant information) in a standard concealed information test (CIT). Participants in the guilty group were instructed to conceal crime-related information they obtained from the mock crime, thus making deceptive response to the probes. Meanwhile, their brain activity to probes and irrelevants was recorded by functional near-infrared spectroscopy (fNIRS). At the group level, we found that probe items were associated with longer reaction times and greater activity in bilateral dorsolateral prefrontal cortex and supplementary motor cortex than irrelevant items in the guilty group, but not in the innocent group. These findings provided evidence on neural correlates of recognition during a CIT. Finally, on the basis of the activity in bilateral dorsolateral prefrontal cortex and supplementary motor cortex, the correct classification of guilty versus innocent participants was approximately 75 % and the combination of fNIRS and reaction time measures yielded a better classification rate of 83.3 %. These findings illustrate the feasibility and promise of using fNIRS to detect concealed information.