Conceptual complexity and the bias/variance tradeoff

In this paper we propose that the conventional dichotomy between exemplar-based and prototype-based models of concept learning is helpfully viewed as an instance of what is known in the statistical learning literature as the bias/variance tradeoff. The bias/variance tradeoff can be thought of as a sliding scale that modulates how closely any learning procedure adheres to its training data. At one end of the scale (high variance), models can entertain very complex hypotheses, allowing them to fit a wide variety of data very closely—but as a result can generalize poorly, a phenomenon called overfitting. At the other end of the scale (high bias), models make relatively simple and inflexible assumptions, and as a result may fit the data poorly, called underfitting. Exemplar and prototype models of category formation are at opposite ends of this scale: prototype models are highly biased, in that they assume a simple, standard conceptual form (the prototype), while exemplar models have very little bias but high variance, allowing them to fit virtually any combination of training data. We investigated human learners’ position on this spectrum by confronting them with category structures at variable levels of intrinsic complexity, ranging from simple prototype-like categories to much more complex multimodal ones. The results show that human learners adopt an intermediate point on the bias/variance continuum, inconsistent with either of the poles occupied by most conventional approaches. We present a simple model that adjusts (regularizes) the complexity of its hypotheses in order to suit the training data, which fits the experimental data better than representative exemplar and prototype models.     

Exploring the mental space of autonomous intentional agents

The ability to infer the intentions of other agents on the basis of their motion is a critical psychological faculty. In the present study, we examine a key question underlying this process, namely: What are the psychologically natural categories of intentional agents and actions? To investigate this question empirically, we use displays containing a number of autonomous, independently programmed agents moving about a two-dimensional environment and interacting with one another. Each agent behaves according to its own simple program, controlled by a small number of parameters that define its "personality." We probe participants' impressions of the similarities among the behaviors of the various agents, and then use multidimensional scaling in an attempt to recover the subjective mental space of agent types. An important variable underlying this space turns out to be a parameter that determines how the agent reacts to a nearby agent at one critical distance. A follow-up experiment suggests that variation along this parameter ultimately contributes to modulating a more fundamental perceptual dimension that reflects how "hostile" or "friendly" the agents appear to be.     

Semantic similarity influences early morphological priming in Serbian: A challenge to form-then-meaning accounts of word recognition

Semantically similar (e.g., coolant-COOL) primes have produced greater facilitation than have form-similar but semantically dissimilar (e.g., rampant-RAMP) primes when English words have appeared in the forward-masked primed lexical decision task (Feldman, O'Connor, & Moscoso del Prado Martín, Psychonomic Bulletin & Review 16: 684-691, 2009). These results challenge claims that form-based, semantically blind activation underlies early morphological facilitation. Some have argued that the English materials in previous studies were not ideally constructed, insofar as the types of spelling changes to affixed stems differed in the semantically similar and dissimilar pairs. The present study exploited Serbian's bialphabetism, rich morphology, and homographic (form-identical) stems to replicate early effects of semantic similarity. Furthermore, it incorporated within-target manipulations of prime type and of alphabet, such that the alphabets of the prime-target pairs matched in Experiment 1a and alternated in Experiment 1b. Importantly, no letter or phoneme changes occurred between the stems of the primes and targets. These results revealed significant effects of semantic similarity that are comparable with and without alphabet alternation. The semantic effects in Serbian replicated almost exactly those in English (Feldman et al., Psychonomic Bulletin & Review 16: 684-691, 2009), which suggests that even early in the course of processing, morphemes are units of meaning as well as of form. The results failed to support models of lexical processing that postulate sequential access, first to the morphological form, and then to the semantic aspects of words.     

Human capital and objective indicators of career success: The mediating effects of cognitive ability and conscientiousness

The purpose of the current study is to examine the mediating processes through which human capital (e.g. education and work experience) contribute to objective indicators of career success (e.g. salaries and promotions). We are particularly interested in the ways in which cognitive ability and conscientiousness help explain the process through which human capital gets translated into performance effectiveness and tangible career attainments. Results from meta‐analytical structural equation modelling show that individuals' cognitive ability and conscientiousness mediate the effects of both education and organizational tenure on in‐role and extra‐role job performance. Ultimately, both in‐role and extra‐role job performance positively influence employees' salaries and promotions. The article concludes with implications for theory development and management practice.     

Treatment adherence among Latina female adolescent suicide attempters

Clinicians must identify factors among suicide-attempting adolescents and their families that increase treatment adherence. Researchers assessed a consecutive series of 140 disenfranchised Latina adolescents (ages 12-18 years) and their mothers presenting at a large urban emergency room after a suicide attempt by the adolescent. Adherence was examined as it related to service delivery, individual background characteristics, and psychosocial factors (current symptomatology, treatment attitudes). Each factor was found to predict adolescent treatment adherence. Adolescents receiving a specialized emergency room program, those with a diagnosis of disruptive behavior disorder, and those from single-parent households attended significantly more therapy sessions compared to their suicide-attempting peers receiving standard emergency room care. Adolescents with a diagnosis of anxiety disorders and those whose mothers reported more psychopathology and perceived more cohesive family relationships tended to attend significantly fewer treatment sessions. The implications for the delivery of emergency room interventions are discussed.     

Can Hope be Changed in 90 Minutes? Testing the Efficacy of a Single-Session Goal-Pursuit Intervention for College Students

Despite extensive research demonstrating relationships between hope and well being, little work addresses whether hope is malleable. We test a single-session, 90-min intervention to increase college students’ hopeful goal-directed thinking (as defined by Snyder et al. in, Pers Soc Psychol 60:570–585, 1991). To date, this study represents the only test of hope’s malleability in fewer than five sessions and contributes to the small but growing literature regarding positive-psychology interventions. This intervention is especially relevant to college students, given the increasing psychological distress and lack of perceived control noted among this population (Lewinsohn et al. in, J Abnorm Psychol 102:110–120, 1993; Twenge et al. in, Pers Soc Psychol Rev 8:308–319, 2004). Ninety-six participants were assigned to the hope intervention or one of two comparison/control conditions—progressive muscle relaxation or no intervention. Assessment occurred prior to intervention (pre-test), following intervention (post-test), and at one-month follow-up. Participants in the hope intervention showed increases in measures of hope, life purpose, and vocational calling from pre- to post-test relative to control participants. They also reported greater progress on a self-nominated goal at one-month follow-up. Counterintuitively, although hope predicted goal progress, hope did not mediate the relationship between intervention condition and goal progress. Implications of these findings and future directions are discussed.     

Curved apparent motion induced by amodal completion

We investigated whether amodal completion can bias apparent motion (AM) to deviate from its default straight path toward a longer curved path, which would violate the well-established principle that AM follows the shortest possible path. Observers viewed motion sequences of two alternating rectangular tokens positioned at the ends of a semicircular occluder, with varying interstimulus intervals (ISIs; 100-500?ms). At short ISIs, observers tended to report simple straight-path motion-that is, outside the occluder. But at long ISIs, they became increasingly likely to report a curved-path motion behind the occluder. This tendency toward reporting curved-path motion was influenced by the shape of tokens, display orientation, the gap between tokens and the occluder, and binocular depth cues. Our results suggest that the visual system tends to minimize unexplained absence of a moving object, as well as its path length, such that AM deviates from the shortest path when amodal integration of motion trajectory behind the curved occluder can account for the objective invisibility of the object during the ISI.