Actions do not speak louder than words in an interactive false belief task.

Traditionally, it had been assumed that meta-representational Theory of Mind (ToM) emerges around the age of 4 when children come to master standard false belief (FB) tasks. More recent research with various implicit measures, though, has documented much earlier competence and thus challenged the traditional picture. In interactive FB tasks, for instance, infants have been shown to track an interlocutor's false or true belief when interpreting her ambiguous communicative acts (Southgate et al. 2010 Dev. Sci. 13, 907-912. (doi:10.1111/j.1467-7687.2009.00946.x)). However, several replication attempts so far have produced mixed findings (e.g. Dörrenberg et al. 2018 Cogn. Dev. 46, 12-30. (doi:10.1016/j.cogdev.2018.01.001); Grosse Wiesmann et al. 2017 Dev. Sci. 20, e12445. (doi:10.1111/desc.12445); Király et al. 2018 Proc. Natl Acad. Sci. USA 115, 11 477-11 482. (doi:10.1073/pnas.1803505115)). Therefore, we conducted a systematic replication study, across two laboratories, of an influential interactive FB task (the so-called 'Sefo' tasks by Southgate et al. 2010 Dev. Sci. 13, 907-912. (doi:10.1111/j.1467-7687.2009.00946.x)). First, we implemented close direct replications with the original age group (17-month-olds) and compared their performance to those of 3-year-olds. Second, we designed conceptual replications with modifications and improvements regarding pragmatic ambiguities for 2-year-olds. Third, we validated the task with explicit verbal test versions in older children and adults. Results revealed the following: the original results could not be replicated, and there was no evidence for FB understanding measured by the Sefo task in any age group except for adults. Comparisons to explicit FB tasks suggest that the Sefo task may not be a sensitive measure of FB understanding in children and even underestimate their ToM abilities. The findings add to the growing replication crisis in implicit ToM research and highlight the challenge of developing sensitive, reliable and valid measures of early implicit social cognition.

Reliability and generalizability of an acted-out false belief task in 3-year-olds.

The current study tested the reliability and generalizability of a narrative act-out false belief task held to reveal Theory of Mind (ToM) competence at 3 years of age, before children pass verbal standard false belief tasks (the "Duplo task"; Rubio-Fernández & Geurts, 2013, Psychological Science). We conducted the task across two labs with methodologically improved matched control conditions. Further, we administered an analogue intensionality version to assess the scope of ToM competence in the Duplo task. 72 3-year-olds participated in a Duplo change-of-location task, a Duplo intensionality task, and half of them in a matched verbal standard change-of-location task, receiving either false belief or matched true belief scenarios. Children performed at chance in the false belief Duplo location change and intensionality tasks as well as in the standard false belief task. There were no differences to the standard task, and performance correlated across all three false belief tasks, revealing a rather unified competence and no task advantage. In the true belief conditions of both Duplo tasks, children performed at ceiling and significantly different from the false belief conditions, while they were at chance in the true belief condition of the standard task. The latter indicates that a pragmatic advantage of the Duplo task compared to the standard task holds only for the true belief scenarios. Our study shows that the Duplo task measures the same ToM competence as the standard task and rejects a notion of earlier false belief understanding on the group level in 3-year-old children.

Female Zebra Finches Smell Their Eggs.

Parental investment in unrelated offspring seems maladaptive from an evolutionary perspective, due to the costs of energy and resources that cannot be invested in related offspring at the same time. Therefore selection should favour mechanisms to discriminate between own and foreign offspring. In birds, much emphasis has been placed on understanding the visual mechanisms underlying egg recognition. However, olfactory egg recognition has almost been completely ignored. Here, we investigated whether female zebra finches (Taeniopygia guttata) are able to discriminate between their own and a conspecific egg based on olfactory cues alone. Zebra finches are colonial-breeding songbirds. Eggs are monomorphic, i.e. without any spotting pattern, and intraspecific brood parasitism frequently occurs. In a binary choice experiment, female zebra finches were given the choice between the scent of their own and a conspecific egg. After the onset of incubation, females chose randomly and showed no sign of discrimination. However, shortly before hatching, females preferred significantly the odour of their own egg. The finding that females are capable to smell their own egg may inspire more research on the potential of olfaction involved in egg recognition, especially in cases where visual cues might be limited.

Female but not male dogs respond to a size constancy violation.

Differences between sexes in cognitive processes are widespread in humans and permeate many, if not most, cognitive domains. In animal cognition research, however, possible sex differences are still often neglected. Here, we provide striking evidence for a sex-specific response in an object permanence task in domestic dogs (Canis familiaris). Female dogs responded with significantly increased looking times to a violation of expectancy--a ball 'magically' changing size while temporarily occluded. By contrast, male dogs, irrespective of their neuter status, did not respond to the size constancy violation. These results indicate that sex differences in basic cognitive processes may extend to mammals in general, and call for increased consideration of possible sex effects when analysing and interpreting data in animal cognition.