What do inferring what a person is thinking or feeling, deciding to report a symptom to your doctor, judging a defendant’s guilt, and navigating a dimly lit room have in common? They involve perceptual uncertainty (e.g., a scowling face might indicate anger or concentration, which engender different appropriate responses), and behavioral risk (e.g., a cost to making the wrong response). Signal detection theory describes these types of decisions. In this tutorial we show how, by incorporating the economic concept of utility, signal detection theory serves as a model of optimal decision making, beyond its common use as an analytic method. This utility approach to signal detection theory highlights potentially enigmatic influences of perceptual uncertainty on measures of decision-making performance (accuracy and optimality) and on behavior (a functional relationship between bias and sensitivity). A “utilized” signal detection theory offers the possibility of expanding the phenomena that can be understood within a decision-making framework.

Although the neurocognitive mechanisms of non-affective language comprehension have been studied extensively, relatively less is known about how the emotional meaning of language is processed. In this study, electrophysiological responses to affectively positive, negative and neutral words, presented within non-constraining, neutral contexts, were evaluated under conditions of explicit evaluation of emotional content (Experiment 1) and passive reading (Experiment 2). In both experiments, a widely distributed Late Positivity was found to be larger to negative than to positive words (a ‘negativity bias’). In addition, in Experiment 2, a small, posterior N400 effect to negative and positive (relative to neutral) words was detected, with no differences found between N400 magnitudes to negative and positive words. Taken together, these results suggest that comprehending the emotional meaning of words following a neutral context requires an initial semantic analysis that is relatively more engaged for emotional than for non-emotional words, while a later, more extended, attention-modulated process distinguishes the specific emotional valence (positive versus negative) of words. Thus emotional processing networks within the brain appear to exert a continuous influence, evident at several stages, on the construction of the emotional meaning of language.

Abstract. ''Peak shift'' is a behavioral response bias arising from discrimination learning in which animals display a directional, but limited, preference for or avoidance of unusual stimuli. Its hypothesized evolutionary relevance has been primarily in the realm of aposematic coloration and limited sexual dimorphism. Here, we develop a novel functional approach to peak shift, based on signal detection theory, which characterizes the response bias as arising from uncertainty about stimulus appearance, frequency, and quality. This approach allows the influence of peak shift to be generalized to the evolution of signals in a variety of domains and sensory modalities. The approach is illustrated with a bumblebee (Bombus impatiens) discrimination learning experiment. Bees exhibited peak shift while foraging in an artificial Batesian mimicry system. Changes in flower abundance, color distribution, and visitation reward induced bees to preferentially visit novel flower colors that reduced the risk of flower-type misidentification. Under conditions of signal uncertainty, peak shift results in visitation to rarer, but more easily distinguished, morphological variants of rewarding species in preference to their average morphology. Peak shift is a common and taxonomically widespread phenomenon. This example of the possible role of peak shift in signal evolution can be generalized to other systems in which a signal receiver learns to make choices in situations in which signal variation is linked to the sender's reproductive success.

The prolonged nursing period and strong, extended mother-infant bond observed among bottlenose dolphins may reflect social and physical ontogeny critical for infant survival. This study was conducted to quantify ontogentic changes in mother-infant contact time and the amount of time infants spent in specific spatial states with their mothers from birth to age 12 mo. These behaviors were studied through a systematic, longitudinal study of six mother-infant pairs of captive bottlenose dolphins from three different social groups. There was a significant decrease in the time infants spent with their mothers (logistic regression, P < 0.00 l), following the general mammalian pattern of increasing independence with age. When with their mothers, the probability that infants would be found in "echelon" position, flanking the mother, decreased as the calf aged (logistic regression, P < O.OOl), possibly due to anatomical and hydrodynamic factors. The probability that infants would be found in "infant" position, underneath the mother, increased with calf age (logistic regression, P < 0.001). Results obtained in this study are consistent with similar studies of wild bottlenose dolphin mother-infant pairs, indicating a suite of ontogenetically comparable behaviors between wild and captive bottlenose dolphins.

3-Iodothyronamine (T1AM) is a metabolite of thyroid hormone. It is an agonist at trace amine-associated receptor 1 (TAAR1), a recently identified receptor involved in monoaminergic regulation and a potential novel therapeutic target. Here, T1AM was studied using rhesus monkey TAAR1 and/or human dopamine transporter (DAT) co-transfected cells, and wild-type (WT) and TAAR1 knock-out (KO) mice. The IC50 of T1AM competition for binding of the DAT-specific radio-ligand [3H]CFT was highly similar in DAT cells, WT striatal synaptosomes and KO striatal synaptosomes (0.72-0.81 μM). T1AM inhibition of 10 nM [3H]dopamine uptake (IC50: WT, 1.4±0.5 μM; KO, 1.2±0.4 μM) or 50 nM [3H]serotonin uptake (IC50: WT, 4.5±0.6 μM; KO, 4.7±1.1 μM) in WT and KO synaptosomes was also highly similar. Unlike other TAAR1 agonists that are DAT substrates, TAAR1 signaling in response to T1AM was not enhanced in the presence of DAT as determined by CRE-luciferase assay. In vivo, T1AM induced robust hypothermia in WT and KO mice equivalently and dose dependently (maximum change degrees Celsius: 50 mg/kg at 60 min: WT -6.0±0.4, KO -5.6±1.0; and 25 mg/kg at 30 min: WT -2.7±0.4, KO -3.0±0.2). Other TAAR1 agonists including beta–phenylethylamine (β-PEA), MDMA (3,4-methylenedioxymethamphetamine) and methamphetamine also induced significant, time-dependent thermoregulatory responses that were alike in WT and KO mice. Therefore, TAAR1 co-expression does not alter T1AM binding to DAT in vitro nor T1AM inhibition of [3H]monoamine uptake ex vivo, and TAAR1 agonist-induced thermoregulatory responses are TAAR1-independent. Accordingly, TAAR1-directed compounds will likely not affect thermoregulation nor are they likely to be cryogens.