Despite an auspicious start from which lasting theories were generated (eg critical periods hypothesis, Scott & Marston 1950), and despite recent modern technology enabling biological investigations of sensory development (eg EEG, fMRI), in the last fifty years little attention has been devoted to the development of puppies’ (Canis lupus f. familiaris) sensory abilities. Attention to puppies’ sensory development is needed for both theoretical and applied purposes, because understanding puppies’ early experiences depends on understanding their perceptual world. This paper reviews the chronology of sensory development in puppies, looking at each sense individually. It then examines the relationships among phases of sensory and neural development and the critical periods proposed by Scott and Marston (1950). With improved knowledge and awareness of canine sensory development, researchers and other practitioners that work with puppies can better assess and improve puppies’ welfare. Therefore, this review should be of interest not only to researchers, but should also be of use to others that interact with dogs (eg shelter workers, dog breeders). By knowing what puppies are able to see, practitioners can visually enrich puppies’ environments. By knowing what puppies are able to taste and smell, practitioners can better predict the preference-related impact of introducing dietary variation to puppies. Knowing when puppies are first, and best, able to hear, see, and otherwise sense people and other animals, practitioners can design and customise programmes of socialisation and systematic exposure of young puppies.

The issue of critical or sensitive periods affecting the outcome of second language (L2) acquisition has been the subject of intense investigation and debate for many years, with people arguing for or against maturational effects on ultimate attainment. In their influential paper, Johnson and Newport (1989) identify two hypotheses: the exercise hypothesis and the maturational state hypothesis. According to the former, if the capacity for acquiring language is exercised early in life (in first language acquisition), then language learning abilities will remain intact throughout life: in other words, permitting successful L2 acquisition regardless of age. In contrast, according to the maturational state hypothesis, the language learning capacity declines with age, affecting L2 acquisition as well as late L1. Johnson and Newport take their results, which show an age-related decline in performance during childhood and adolescence, to support the maturational state hypothesis. Many L2 researchers have adopted a maturational perspective and have reached similar conclusions as to the presence of critical or sensitive periods (e.g., Abrahamsson, 2012; DeKeyser & Larson-Hall, 2005; Long, 1990; Oyama, 1976; Patkowski, 1980). Some researchers have pointed out that age effects continue into adulthood, contrary to the claim for a critical period (e.g., Birdsong & Mollis, 2001). Others have suggested that what looks like an age-related maturational decline may be accounted for by confounding factors, such as task effects, effects of L1, amount of L2 use, education or input (e.g., Bialystok & Miller, 1999; Flege, Yeni-Komshian & Liu, 1999).

Human development reportedly includes critical and sensitive periods during which environmental stressors can affect traits that persist throughout life. Controversy remains over which of these periods provides an opportunity for such stressors to affect health and longevity. The elaboration of reproductive biology and its behavioral sequelae during adolescence suggests such a sensitive period, particularly among males. We test the hypothesis that life expectancy at age 20 among males exposed to life-threatening stressors during early adolescence will fall below that among other males. We apply time-series methods to cohort mortality data in France between 1816 and 1919, England and Wales between 1841 and 1919, and Sweden between 1861 and 1919. Our results indicate an inverse association between cohort death rates at ages 10–14 and cohort life expectancy at age 20. Our findings imply that better-informed and more strategic management of the stressors encountered by early adolescents may improve population health.

To what extent, if any, does Universal Grammar (UG) constrain second language (L2) acquisition? This is not only an empirical question, but one which is currently investigable. In this context, L2 acquisition is emerging as an important new domain of psycholinguistic research. Three logical possibilities have been articulated regarding the role of UG in L2 acquisition: The first is the “no access” hypothesis that claims that no aspect of UG is available to the L2 learner. The second is the “partial access” hypothesis that claims that only LI instantiated principles and LI instantiated parameter-values of UG are available to the learner. The third, called the “full access” hypothesis, asserts that UG in its entirety constrains L2 acquisition.

In this paper we argue that there is no compelling evidence to support either of the first two hypotheses. Moreover, we provide evidence concerning functional categories in L2 acquisition consistent with the claim that UG is fully available to the L2 learner (see also Flynn 1987; Li 1993; Martohardjono 1992; Schwartz & Sprouse 1991; Thomas 1991; White 1989). In addition, we will attempt to clarify some of currently unclear theoretical issues that arise with respect to positing UG as an explanatory theory of L2 acquisition. We will also investigate in some detail certain crucial methodological questions involved in experimentally testing the role of UG in L2 acquisition and finally, we will present a set of experimental results of our own supporting the “Full Access” hypothesis.

According to a “selective” (as opposed to “instructive”) model of human language capacity, people come to know more than they experience. The discrepancy between experience and eventual capacity (the “poverty of the stimulus”) is bridged by genetically provided information. Hence any hypothesis about the linguistic genotype (or “Universal Grammar,” UG) has consequences for what experience is needed and what form people's mature capacities (or “grammars”) will take. This BBS target article discusses the “trigger experience,” that is, the experience that actually affects a child's linguistic development. It is argued that this must be a subset of a child's total linguistic experience and hence that much of what a child hears has no consequence for the form of the eventual grammar. UG filters experience and provides an upper bound on what constitutes the triggering experience. This filtering effect can often be seen in the way linguistic capacity can change between generations. Children only need access to robust structures of minimal (“degree-0”) complexity. Everything can be learned from simple, unembedded “domains” (a grammatical concept involved in defining an expression's logical form). Children do not need access to more complex structures.