Perceived Correctness of Nominal Gender (Dis)Agreement by Heritage Speakers of Spanish

This study investigates how quantity of exposure to Spanish as well as early language acquisition affects the ability of adult Spanish heritage speakers to perceive prescriptively (in)correct nominal gender agreement in three-word sequences of a noun with two modifiers. Thirty-six adult speakers of Spanish as a heritage language listened to 116 different three-word sequences, half of which contained prescriptively incorrect gender or number agreement. Participants were asked to determine if the phrase sounded right. Half of the test items were experimental and addressed gender agreement, while the other half were distractors based on number agreement. Furthermore, participants filled out the Bilingual Language Profile (Birdsong et al., 2012) to assess their exposure to and comfort with Spanish. As in many previous studies, participants had more difficulty identifying a prescriptively incorrect stimulus as incorrect than correct stimuli as correct. There was a split between sequential and simultaneous bilinguals: while increased Spanish exposure improved sequential bilinguals’ ability to accurately identify both correct and incorrect stimuli, simultaneous bilinguals only saw gains in their ability to identify correct stimuli.

Distinct prestimulus and poststimulus activation of VTA neurons correlates with stimulus detection

Dopamine neurons of the ventral tegmental area (VTA) signal the occurrence of a reward-predicting conditioned stimulus (CS) with a subsecond duration increase in post-CS firing rate. Important theories about reward-prediction error and reward expectancy have been informed by the substantial number of studies that have examined post-CS phasic VTA neuron activity. On the other hand, the role of VTA neurons in anticipation of a reward-predicting CS and analysis of prestimulus spike rate rarely has been studied. We recorded from the VTA in rats during the 3-choice reaction time task, which has a fixed-duration prestimulus period and a difficult-to-detect stimulus. Use of a stimulus that was difficult to detect led to behavioral errors, which allowed us to compare VTA activity between trials with correct and incorrect stimulus-guided choices. We found a sustained increase in firing rate of both putative dopamine and GABA neurons during the pre-CS period of correct and incorrect trials. The poststimulus phasic response, however, was absent on incorrect trials, suggesting that the stimulus-evoked phasic response of dopamine neurons may relate to stimulus detection. The prestimulus activation of VTA neurons may modulate cortical systems that represent internal states of stimulus expectation and provide a mechanism for dopamine neurotransmission to influence preparatory attention to an expected stimulus.

Learning Increases Stimulus Salience in Anterior Inferior Temporal Cortex of the Macaque

With experience, an object can become behaviorally relevant and thereby quickly attract our interest when presented in a visual scene. A likely site of these learning effects is anterior inferior temporal (aIT) cortex, where neurons are thought to participate in the filtering of irrelevant information out of complex visual displays. We trained monkeys to saccade consistently to one of two pictures in an array, in return for a reward. The array was constructed by pairing two stimuli, one of which elicited a good response from the cell when presented alone (“good” stimulus) and the other of which elicited a poor response (“poor” stimulus). The activity of aIT cells was recorded while monkeys learned to saccade to either the good or poor stimulus in the array. We found that neuronal responses to the array were greater (before the saccade occurred) when training reinforced a saccade to the good stimulus than when training reinforced a saccade to the poor stimulus. This difference was not present on incorrect trials, i.e., when saccades to the incorrect stimulus were made. Thus the difference in activity was correlated with performance. The response difference grew over the course of the recording session, in parallel with the improvement in performance. The response difference was not preceded by a difference in the baseline activity of the cells, unlike what was found in studies of cued visual search and working memory in aIT cortex. Furthermore, we found similar effects in a version of the task in which any of 10 possible pairs of stimuli, prelearned before the recording session, could appear on a given trial, thereby precluding a working memory strategy. The results suggest that increasing the behavioral significance of a stimulus through training alters the neural representation of that stimulus in aIT cortex. As a result, neurons responding to features of the relevant stimulus may suppress neurons responding to features of irrelevant stimuli.

Attention in HIV-infected children: Results from the Hemophilia Growth and Development Study

Attentional functioning was examined in three groups of 7- to 19-year-old male participants with hemophilia: (1) HIV seronegative controls (HIV−, N = 66), (2) HIV seropositive participants with CD4+ lymphocyte counts greater than or equal to 200 (HIV+ CD4+ ≥200, N = 79), and (3) severely immune suppressed HIV seropositive participants (HIV+ CD4+ <200, N = 28). Two measures sensitive to attention deficits were used: the Continuous Performance Test (CPT) and the Span of Apprehension (Span). On the CPT, there was a decrement in attention in both HIV+ groups, as indexed by an increase in false alarm rate from Block 1 to Block 3, that was not present in the HIV− group. The longer the HIV+ children were required to sustain attention to the CPT, the more they responded to the incorrect stimulus. This effect decreased as age increased. Span percent correct and latency to correct were associated with the presence of a premorbid history of intracerebral hemorrhage, but were not sensitive to HIV status or degree of immune suppression in the HIV+ children, suggesting morbidity related to hemophilia. The remaining CPT and Span variables—hit rate, sensitivity, latency, percent correct, and latency to correct—showed the expected associations with age, but none showed conclusive associations with HIV status or immune suppression in the HIV+ participants. (JINS, 2000, 6, 443–454.)

Emergent Simple Discrimination in Children: Transfer of Stimulus Control under Non-Reinforced Conditions

Previous research on humans suggests that simple discriminations may emerge if both stimuli, B1 and B2, are compounded with the stimuli of a previously trained discrimination, A1 (S+) and A2 (S-), and responding to the compounds, B1A1 and B2A2, is reinforced. Two questions were addressed. First, do simple discriminations also emerge if (a) only one stimulus, B1, is compounded with a training stimulus, A1 (S+) or A2 (S-); or with both training stimuli, A1 (S+) and A2 (S-); and (b) neither B1 nor B2 is compounded with the training stimuli? Second, do simple discriminations emerge if reinforcement in the presence of the AB compounds is withheld? Normal preschool children served as subjects. The study consisted of six experiments. Transfer occurred in all experiments regardless of whether both test stimuli, one test stimulus, or none of the test stimuli were compounded with the training stimuli under non-reinforced conditions. The results can be described by the following rules: Respond to any stimulus that includes a component of a “correct” stimulus of a previous discrimination. Otherwise, respond away from the stimulus that incorporates a component from an “incorrect” stimulus of a previous discrimination. The implications of data for sensory pre-conditioning and language-based accounts are discussed.

Eye Orientation during Visual Discrimination Learning by Humans

Motion pictures were taken of the eyes of human Ss as they learned simultaneous two-choice pattern discriminations. Each trial was analyzed in two parts: the pre-stimulus phase (time before the onset of the stimuli) and the stimulus phase (time during which the stimuli were present). Ss looked more at one of the two discriminanda (the left or right) during one or both of those phases of the trial. These gaze-position preferences were not accompanied by response-position preferences, nor were there any correlations between eye, hand, and gaze preferences. In addition, all Ss looked more at the correct than at the incorrect stimulus.

Prompted vs Trial-and-Error Concept Discrimination Learning in Monkeys

8 test-sophisticated rhesus monkeys were tested on concept discrimination problems under conventional trial-and-error (TE) procedures and two forms of prompting, i.e., conditions in which an established cue was temporarily available for solution of the problem. Positive Prompting (PP) included a cue attached to the correct stimulus of the discrimination pair; Negative Prompting (NP), a cue attached to the incorrect stimulus. The data revealed significantly better intraproblem learning following NP than following equivalent amounts of either PP or TE.