Differences In Rate Of Acquisition Research Articles

The Impact of Universal Glove and Gown Use on Clostridioides Difficile Acquisition: A Cluster-Randomized Trial.

Clostridioides difficile is the most common cause of healthcare-associated infections in the United States. It is unknown whether universal gown and glove use in intensive care units (ICUs) decreases acquisition of C. difficile. This was a secondary analysis of a cluster-randomized trial in 20 medical and surgical ICUs in 20 US hospitals from 4 January 2012 to 4 October 2012. After a baseline period, ICUs were randomized to standard practice for glove and gown use versus the intervention of all healthcare workers being required to wear gloves and gowns for all patient contact and when entering any patient room (contact precautions). The primary outcome was acquisition of toxigenic C. difficile determined by surveillance cultures collected on admission and discharge from the ICU. A total of 21 845 patients had both admission and discharge perianal swabs cultured for toxigenic C. difficile. On admission, 9.43% (2060/21 845) of patients were colonized with toxigenic C. difficile. No significant difference was observed in the rate of toxigenic C. difficile acquisition with universal gown and glove use. Differences in acquisition rates in the study period compared with the baseline period in control ICUs were 1.49 per 100 patient-days versus 1.68 per 100 patient-days in universal gown and glove ICUs (rate difference, -0.28; generalized linear mixed model, P = .091). Glove and gown use for all patient contact in medical and surgical ICUs did not result in a reduction in the acquisition of C. difficile compared with usual care. NCT01318213.

Study on Image Acquisition of Transthoracic Echocardiography in Mechanically Ventilated ICU Patients

Objective This study aimed to determine which parameters in transthoracic echocardiography (TTE) are more likely to be affected when applied in a critical care setting with mechanical ventilation.Methods Ninety mechanically ventilated ICU patients were enrolled into the study group. The control group consisted of 90 patients who underwent interventional therapy. All patients had bedside TTE for parametric measurements including the right ventricular size, septal kinetics and left ventricular ejection fraction (LVEF) by eyeballing (visual assessment), the tricuspid annular plane systolic excursion (TAPSE), mitral annular plane systolic excursion (MAPSE) by M-mode sonography, the right ventricular outflow tract velocity-time integral (RVOT VTI) and left ventricular outflow tract velocity-time integral (LVOT VTI) by pulse-Doppler, the right ventricular fraction of area change (FAC) and left ventricular ejection fraction (LVEF Simpson) by endocardium tracing. We compared the differences in the frequency of optimal image acquisition in assessments of these parameters between the two groups, as well as the differences in acquisition rates of parameter measurements in ventilated ICU patients.Results There were significantly fewer patients in the study group than in the control group who had optimal images acquisitions for parameter assessments with M-mode method, pulse Doppler method and endocardium-tracing method (P<0.05); no significant difference was obsered in the number of patients with optimal images for RV eyeballing and LVEF eyeballing between the two groups. In the study group, significantly fewer optimal images were acquired for FAC than for TAPSE (22.2% vs. 72.2%, χ2=45.139, P<0.001) and RVOT VTI (22.2% vs. 71.1%, χ2=43.214, P<0.001); there were also fewer optimal images acquired for LVEF Simpson than for MAPSE (37.8% vs. 84.4%, χ2=41.236, P<0.001) and LVOT VTI (37.8% vs. 85.6%, χ2=43.455, P<0.001).Conclusions Images acquisition of optimal TTE images tend to be difficult in mechanically ventilated ICU patients, but eyeballing method for functional evaluation could be an alternative method. For quantitative parameters measurements, M-mode based longitudinal function evaluation and pulse Doppler-based VTI were superior to the endocardium-tracing based parameter assessments.

Sex Differences in Heroin Self‐Administration Behaviors and Heroin‐Induced Receptor Alterations in Rats

Despite reports that women are more vulnerable than men to certain features of heroin addiction, including craving and relapse, there are limited numbers of preclinical studies evaluating these phenomena. In addition, the published sex‐comparison studies in preclinical models of heroin addiction have shown conflicting results. For example, Lynch and Carroll (1999) report that female rats acquire heroin self‐administration faster than males, while Stewart et al. 1996 report no differences in acquisition rates between male and female rats. Therefore, this study examined sex differences in several heroin self‐administration behaviors and putative neural correlates. Adult male and female Sprague‐Dawley rats were implanted with jugular catheters and were given access to heroin (FR1 schedule of reinforcement, 0.025 mg/kg/inf; maximum 20 infusions) for 6 hours per day. Acquisition criteria were met when rodents earned all 20 infusions for 2 consecutive days. After acquisition, all animals were placed on a long access (LgA) paradigm, which included unlimited access to heroin (FR1) for 6 hours/day for 10 consecutive days. After completion of LgA, animals were tested for motivation to self‐administer heroin using a progressive ratio (PR) schedule. Finally, we measured basal dopamine dynamics and the ability of kappa opioid receptor (KOR) and D2/D3 autoreceptor agonism to reduce dopamine release in the nucleus accumbens following exposure to heroin self‐administration using ex vivo fast scan cyclic voltammetry (FSCV) in brain slices. Female and male rats acquired heroin self‐administration at similar rates, but females self‐administered more heroin during LgA, had increased loading doses of heroin during the first 10 minutes of LgA sessions, and increased escalation of intake across the 10 LgA sessions compared to males. PR data revealed a rightward shift in the dose‐response curve of the females, indicative of increased motivation to obtain higher doses of heroin. Using FSCV, we found that all rats displayed greater KOR‐ and D3 autoreceptor‐mediated dopamine release inhibition, however, females showed higher levels of activity for both receptors. These results reveal marked sex differences in specific heroin self‐administration behaviors that may be driven by altered receptor functioning within the nucleus accumbens. Future studies elucidating receptor interactions related to sexually dimorphic heroin self‐administration behaviors in rats will be highly informative.Support or Funding InformationT32 DA041349This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Grouping subjects based on conditioning criteria reveals differences in acquisition rates and in strength of conditioning-specific reflex modification

Averaging behavioral data such as the nictitating membrane response (NMR) across subjects can conceal important individual and group differences. Analyses were conducted of NMR data from rabbits that were grouped based on the point during NMR conditioning when subjects produced 8 conditioned responses (CR) in a set of 10 trials. This resulted in five groups (Early Day 1, Late Day 1, Early Day 2, Late Day 2, Early Day 3) in which group differences in CR acquisition rates were found. Percent (%) CRs were not found to increase monotonically and between-session differences in % CR were found. Conditioning-specific reflex modification (CRM) of the NMR is a type of enhanced reflexive responding of the NMR that is detected when the unconditioned stimulus (US) is presented in the absence of the conditioned stimulus (CS) following paired classical conditioning. CRM occurred in some subjects in all five groups. Subjects from both the group that was fastest and the group that was slowest to reach the learning criterion had unconditioned response (UR) topographies following NMR conditioning that strongly resembled the CR-UR response sequence elicited during NMR conditioning. This finding was most pronounced when the US duration used to assess CRM was equivalent to that used during NMR conditioning, further evidence to support the hypothesis that CRM is a CR that has generalized from the CS to the US. While grouping data based on conditioning criteria did not facilitate identifying individuals more predisposed to exhibiting CRM, strong CRM only occurred in the groups that reached the conditioning criterion the fastest.

Family History of Alzheimer's Disease is Associated with Impaired Perceptual Discrimination of Novel Objects.

Early detection may be the key to developing therapies that will combat Alzheimer’s disease (AD). It has been consistently demonstrated that one of the main pathologies of AD, tau, is present in the brain decades before a clinical diagnosis. Tau pathology follows a stereotypical route through the medial temporal lobe beginning in the entorhinal and perirhinal cortices. If early pathology leads to very subtle changes in behavior, it may be possible to detect these changes in subjects years before a clinical diagnosis can currently be made. We aimed to discover if cognitively normal middle-aged adults (40–60 years old) at increased risk for AD due to family history would have impaired performance on a cognitive task known to challenge the perirhinal cortex. Using an oddity detection task, we found that subjects with a family history of AD had lowered accuracy without demonstrating differences in rate of acquisition. There were no differences between subjects’ medial temporal lobe volume or cortical thickness, indicating that the changes in behavior were not due to significant atrophy. These results demonstrate that subtle changes in perceptual processing are detectable years before a typical diagnosis even when there are no differences detectable in structural imaging data. Anatomically-targeted cognitive testing may be useful in identifying subjects in the earliest stages of AD.

The effects of differential outcomes on learning and memory in young and aged rats

It is claimed that using a differential outcomes procedure (DOP) generally results in (1) a faster acquisition of discrimination and (2) less disruption in accuracy when a delay interval is inserted between the stimulus cue and the opportunity to respond; this effect is best known as the differential outcomes effect (DOE). The DOE has been especially evident in aged participants. However, when acquisition in a matching-to-position task under DOP was compared to that under a non-differential outcomes procedure (NDO) by Savage, Pitkin, and Careri (1999), no difference in rate of acquisition was found between young and old rats. In the present experiment, we evaluated the effect of using a differential outcomes procedure on both learning and memory in young (3 months) and aged (24 months) rats in a more standard two-choice stimulus discrimination task. The results reported in this article showed in both young and aged subjects that DOP led to faster acquisition and less disruption in the percentage of correct responses as the delay interval was lengthened. These results confirm that employing DOP is an effective training strategy that can increase speed of acquisition and enhance memory in both young and aged subjects, with larger effects being seen in older rats.

Age difference in dual-task interference effects on procedural learning in children

The current study aimed to investigate the role played by explicit mechanisms during procedural learning in two age groups of children (7 and 10years) using a dual-task paradigm. To do this, we explored the effect of an interference task during the early and late phases of a mirror tracing learning task. The results showed a differential impact of the secondary task on the two age groups, but only during the first learning phase; the performance of 10-year-olds was affected by the second task, whereas in 7-year-olds no performance difference was found between the single- and dual-task conditions. Overall, our study suggests that there are differences in the amount of effortful processing in which 7- and 10-year-olds engage at the beginning of the learning process; procedural learning in young children is mainly implicit, as attested by its lesser sensitivity to an interference task, whereas high-level explicit mechanisms seem to contribute to the procedural performance of 10-year-olds. However, these explicit mechanisms, even if they have an effect on performance, might not have an impact on the learning curve given that no difference in rate of acquisition was found between age groups. These findings are discussed in the light of classical conceptions of procedural learning.

HIV-1 Genetic Variability and Clinical Implications.

Despite advances in antiretroviral therapy that have revolutionized HIV disease management, effective control of the HIV infection pandemic remains elusive. Beyond the classic non-B endemic areas, HIV-1 non-B subtype infections are sharply increasing in previous subtype B homogeneous areas such as Europe and North America. As already known, several studies have shown that, among non-B subtypes, subtypes C and D were found to be more aggressive in terms of disease progression. Luckily, the response to antiretrovirals against HIV-1 seems to be similar among different subtypes, but these results are mainly based on small or poorly designed studies. On the other hand, differences in rates of acquisition of resistance among non-B subtypes are already being observed. This different propensity, beyond the type of treatment regimens used, as well as access to viral load testing in non-B endemic areas seems to be due to HIV-1 clade specific peculiarities. Indeed, some non-B subtypes are proved to be more prone to develop resistance compared to B subtype. This phenomenon can be related to the presence of subtype-specific polymorphisms, different codon usage, and/or subtype-specific RNA templates. This review aims to provide a complete picture of HIV-1 genetic diversity and its implications for HIV-1 disease spread, effectiveness of therapies, and drug resistance development.

Chronic Treatment with Extended Release Methylphenidate Does Not Alter Dopamine Systems or Increase Vulnerability for Cocaine Self-Administration: A Study in Nonhuman Primates

Despite the widespread use of stimulant medications for the treatment of attention deficit hyperactivity disorder, few studies have addressed their long-term effects on the developing brain or susceptibility to drug use in adolescence. Here, we determined the effects of chronic methylphenidate (MPH) treatment on brain dopamine (DA) systems, developmental milestones, and later vulnerability to substance abuse in juvenile nonhuman primates. Male rhesus monkeys (approximately 30 months old) were treated daily with either a sustained release formulation of MPH or placebo (N=8 per group). Doses were titrated to achieve initial drug blood serum levels within the therapeutic range in children and adjusted throughout the study to maintain target levels. Growth, including measures of crown-rump length and weight, was assessed before and after 1 year of treatment and after 3-5 months washout. In addition, positron emission tomography scans were performed to quantify binding availability of D2/D3 receptors and dopamine transporters (DATs). Distribution volume ratios were calculated to quantify binding of [¹⁸F]fluoroclebopride (DA D2/D3) and [¹⁸F]-(+)-N-(4-fluorobenzyl)-2β-propanoyl-3β-(4-chlorophenyl)tropane (DAT). Chronic MPH did not differentially alter the course of weight gain or other measures of growth, nor did it influence DAT or D2/D3 receptor availability after 1 year of treatment. However, after washout, the D2/D3 receptor availability of MPH-treated animals did not continue to decline at the same rate as control animals. Acquisition of intravenous cocaine self-administration was examined by first substituting saline for food reinforcement and then cocaine doses (0.001-0.1 mg/kg per injection) in ascending order. Each dose was available for at least five consecutive sessions. The lowest dose of cocaine that maintained response rates significantly higher than saline-contingent rates was operationally defined as acquisition of cocaine reinforcement. There were no differences in rates of acquisition, overall response rates, or cocaine intake as a function of cocaine dose between groups. In an animal model that closely mimics human development; chronic treatment with therapeutic doses of sustained release MPH did not have a significant influence on the regulation of DATs or D2/D3 receptors, or on standard measures of growth. Furthermore, this treatment regimen and subsequent drug washout did not have an impact on vulnerability to cocaine abuse.

DEVELOPMENT OF KEY‐PECKING, PAUSE, AND AMBULATION DURING EXTENDED EXPOSURE TO A FIXED‐INTERVAL SCHEDULE OF REINFORCEMENT

Six pigeons key-pecked under a fixed-interval (FI) 3-min schedule of food presentation. Each pigeon was studied for 200 daily sessions with 15 intervals per session (3,000 total food presentations). Analyses included the examination of latency to first peck (pause), mean rate of key pecking, and ambulation. Characterizations of stable performance were assessed across measures of behavior and evaluated using commonly employed stability criteria. Stability of response rate and pause was identified better by assessments that evaluated variability and trend, rather than just variability. Between-subject differences in rate of acquisition and terminal values of steady-state performance of pause were observed, and stable pause durations took longer to develop than did stable key-pecking rates. Relative variability in response rate and pause duration decreased as the means increased. A temporally organized pattern of key-pecking (the so-called FI scallop) developed within 50 sessions of exposure to the schedule. Overall ambulation decreased during the early sessions of exposure and further analyses showed greater rates of ambulation during the pause than after it for 4 of the 6 pigeons. Performance under the FI 3-min schedule developed relatively slowly, and key-pecking, pause, and ambulation developed at different rates.

Language typology and the acquisition of bare noun/DP contrasts

Language typology and the acquisition of bare noun/DP contrasts Ana T. Pérez-Leroux, Anna Gavarró Algueró, and Thomas Roeper 1. Introduction If compositionality (the assumption that the meaning of an utterance is determined by the meaning of its parts and the way they combine) is an inherent property of the human language, we expect children to attribute meaning to even small differences in sentence form. The input contains minimal contrasts as in (1), whose interpretation may not be easy to disambiguate in a given discourse context. Our goal is examine how children acquire these minimal distinctions. 1. a. Someone is wearing gloves. b. Someone is wearing the gloves. Formally, these cases differ in the presence of a determiner in contrast with a bare form. Referentially, (1a) includes (1b), so for every context where (1b) is true (1a) is also true. The definite DP has a distinct signature in the input, as it is more frequent at second mention of a referent (Sneed 2008). The bare noun is less specified, and thus less falsifiable. We propose to explore the acquisition of nominal mapping in terms of the semantic competition between bare nouns and DPs. We present a comparative study of two languages: Catalan, where these nominal contrasts occur in restricted positions, and English, where the contrast is instantiated in both subject and object position. To this purpose, we replicated in English Gavarró et al.'s (2006) study on the acquisition of bare/DP objects in Catalan. 2. DP/Bare Noun Contrasts The now-familiar typology in Chierchia (1998) states that languages vary according to how nominal categories are mapped into semantic types. In his Nominal Mapping Parameter (NMP), nouns are associated with two independent features that determine their denotation. The feature [+arg(ument)] indicates N is kind-denoting and has a mass syntax; the feature [+pred(icate)] determines that a N is predicate-denoting and has a countable syntax. In Chinese, and other classifier languages, Ns are mapped as [+arg, -pred] and thus can be arguments in their own right. In Romance languages, Ns are mapped as [-arg, +pred] and need a determiner to function as arguments. In Germanic languages, Ns are mapped as [+arg, +pred]: when Ns are [+pred] they [End Page 413] require a D, as in Romance count nouns; when [+arg] they act like mass nouns. In Romanian, Catalan, Spanish and Italian, bare objects appear in the immediate domain of a P or V head. This is productive for mass and plural count nouns, and lexically restricted for bare singular count nouns (Bosque 1996, Dobrovie-Sorin et al. 2006). Chierchia's approach analyzes the bare objects in (2) differently despite their comparable distribution and interpretation. Milk in (2a) is treated as a bare noun, while llet in (2b) is a DP with a null determiner head. 2. a. Children drink milk. b. Catalan: Els nens beuen llet. The-PL children drink milk. 3. Acquisition of Bare/DP Contrasts Research on the acquisition of DPs has identified typological variation in the timing of the acquisition of determiners. Lleó and Demuth (1999) showed that young Spanish children achieved adult levels of article production earlier than German-speaking children and proposed that prosodic differences across languages determine children's rates of determiner insertion. Guasti, Gavarró, de Lange, and Caprin (2008) examined determiner production in Catalan, Italian, and Dutch children under the age of 3, divided in groups according to linguistic development rather than age. While articles or protoarticles emerged at the same age across languages, there was a clear contrast in the overall rates of use and the pace of development, following the predictions of the NMP. At the initial stage, Catalan and Italian children had article omissions in roughly half of the NPs produced, but dropped substantially under 16% by the second stage. In contrast, Dutch children started with higher omission rates (92%) in the first stage and retained substantial omission rates in the later stage (39%). Guasti and colleagues note that Dutch is statistically different from Catalan and Italian, and conclude that differences in acquisition rates for the various language types exist beyond the effect of prosodic factors. Bilingual children learning Germanic and Romance languages exhibit comparable...

Nasopharyngeal Carriage of Streptococcus pneumoniae in Gambian Infants: A Longitudinal Study

To prepare for national introduction of a pneumococcal conjugate vaccine of restricted valency, we studied nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants. We studied 236 infants in 21 villages. We collected nasopharyngeal swab samples at birth, twice per month for 6 months, and every second month until 1 year of age. We studied time to acquisition and duration of pneumococcal carriage according to serotype. All infants carried S. pneumoniae at some point. Sixty-five serotypes were found, and the 5 most common serotypes (6B, 19F, 6A, 14, and 23F) accounted for 51% of isolates. The mean age at first acquisition of carriage was 33 days (95% confidence interval, 29-36 days). There were no significant differences in acquisition rates between the 6 most common serotypes (P = .067) or between vaccine serotypes, vaccine-related serotypes, or nonvaccine serotypes (P = .317). However, the duration of carriage differed significantly between the 6 most common serotypes (P = .004). The rate of reacquisition of carriage and the duration of carriage did not differ significantly between the 6 most common serotypes (P = .229 and P = .669 respectively). However, nonvaccine types were acquired faster (P = .004) and were carried for a shorter duration (P < .001) than were vaccine serotypes. A previous episode of serotype 14 carriage was associated with delayed reacquisition of this serotype (P = .005) and longer duration of carriage (P = .017). The data provided in this study regarding time to acquisition and duration of pneumococcal carriage in Gambian infants provide an important baseline for evaluating the impact of the introduction of a pneumococcal conjugate vaccine in The Gambia and elsewhere in Africa.

Trial and intertrial durations in Pavlovian conditioning: Issues of learning and performance.

Four experiments assessed the effects of trial (T) and intertrial (I) durations on magazine approach behavior in rats. In Experiments 1 and 2, different groups of animals were conditioned with various combinations of I and T durations. The rate of acquisition, in terms of the number of trials required to reach various acquisition criteria, generally was faster in groups trained with large I:T ratios. There also were differences in rate of acquisition and terminal response rates between groups trained with identical I:T ratios but with different absolute I and T durations. Differences evident at the end of conditioning persisted during a common test with various combinations of I and T durations. Experiments 3 and 4 provided a more specific test of the predictions of 2 general classes of theories and found results that were consistent with those theories that characterize group differences as indicative of differences in learning, rather than in performance.

Schedule-controlled behavior as an index of the development and loss of ethanol tolerance in the rat.

Twelve male Sprague-Dawley rats, following training on one of two food-motivated operant schedules (Fixed-Ratio 30 or Variable Interval 30 s), were exposed to an escalating regimen of daily ethanol (1.125-3.0 g/kg, IP) administration. This increasing dose regimen continued until the maximally tolerable dose for each subject was reached. Tolerance was then monitored for approximately 6 months by periodic ethanol challenge doses (1.5 g/kg). Dose-effect curves (DECs) were obtained prior to chronic ethanol (DEC1), immediately after ethanol tolerance development (DEC2), and 6 months (DEC3) following termination of ethanol exposure. At DEC1, ethanol produced dose-dependent decreases in rate on both schedules with no significant schedule differences in ED50 (the dose effective at reducing the maximal response rate by one-half) values. Maximal tolerance was achieved in means of 46 and 55 days on the VI and FR schedules, respectively. Differences in rate of tolerance acquisition on the initial dose of the chronic regimen (1.125 g/kg) account for most of the difference in the overall rate of acquisition. Comparison of the ED50 data from DECs 1 and 2 indicated that daily ethanol exposure resulted in a 2-fold decrease in ethanol sensitivity (i.e., tolerance) on both operant schedules. The ED50 data from DECs 1 and 3 demonstrated a 1.7-fold decrease in ethanol potency on DEC3. This duration of tolerance was considerably longer than that generally reported, and possibly related to the extended ethanol exposure and the sensitivity of operant schedules to drug effects.

ACQUISITION OF ENGLISH STRUCTURES: A CASE STUDY OF AN ADULT NATIVE SPEAKER OF ARABIC IN AN ENGLISH‐SPEAKING ENVIRONMENT

Little is known about second language acquisition by adults in a natural (non‐classroom) setting. The longitudinal case study reported in this paper provides some information about the early stages through which the adult subject of this study progressed in acquiring English and about the factors affecting her language development. Comparison with the developmental sequence in first language acquisition reveals a striking similarity. This suggests a similarity in underlying processes of adult and child learning. The differences in rate of acquisition may be accounted for in terms of exposure, need, and factors inhibiting practice.

The Effects of Practice Distribution on the Acquisition of Three Discrete Motor Skills

Abstract Eighty male college students were divided into two experimental groups practicing three criterion tasks: the floor kip, the front hip circle mount on the low horizontal bar, and the glide kip on the low horizontal bar. These tasks were practiced under different conditions of massed or distributed practice and an ANCOVA was used to test for significant mean differences in the rates of learning between the experimental groups on each task. The subjects' performance on the Metheny-Johnson test served as the control variable in the analysis and the .05 level of significance was selected. All observed differences in mean rates of acquisition between groups were within the limits of chance on all tasks, regardless of the method of practice. This apparent lack of effect of distribution of practice was attributed to factors such as the pacing of the task, the discrete and complex, rather than continuous, nature of the task, and the learning-performance distinction.

The interaction of emotional stress and language development: Case studies of three visually impaired children

The diagnostic assessment of speech and language function in the first 6 years of life is an important clinical procedure. Although scales measuring verbal and communication skills, and articulatory competence, exist, their value as predictive instruments has not been generally accepted by clinicians. We assume that this is due to the wide individual differences in rate of acquisition of language, and the vulnerability to stress of any function in the process of development. These factors, the child’s rate of acquisition and response to stress and stimulation, are part of the diagnostic assessment. We view stress and stimulation as having a nonspecific cause and effect relationship. For example, one child may respond to separation from the maternal figure by deviation in pronunciation, another by mutism, and still another by behavioral symptoms, while there are other children who would show no observable consequence to such trauma. Likewise, the stimulation of an intervention program may be responded to in different ways. These assumptions have been used as guidelines in the Pre-School Program for Visually Handicapped Children at the New York Association for the Blind, where longitudinal as well as cross-sectional studies are used for the full evaluation of language function. The visually impaired child relies to an even greater extent than the sighted child on verbal language. For him in particular, the ability to develop language will determine the extent of his successful adaptation to life. Attention to early development of language and the design of early intervention procedures are of central importance to our work with preschool children. There are three groups of children in which language and speech may not develop adequately or at all. The first are those who have impaired auditory functions. The second are those who have central nervous system dysfunctions, and the third are those who have experienced serious emotional deprivation or trauma. When language development is deficient, the child’s intellectual and emotional growth may be seriously affected.

Unconditioned and Conditioned Suppression in Two Closely Related Genetic Lines of Chickens

White Plymouth Rock chickens, bidirectionally selected for weight, were trained to keypeck for water. No between-line differences in rate of acquisition or asymptotic level of performance were apparent. Subjects from both weight lines were then assigned to either a forward- or backward-conditioning group, with a white noise CS and a shock UCS. No line or conditioning group showed unconditioned suppression. Forward-conditioning groups of both lines showed significantly more conditioned suppression than backward-conditioning groups. Furthermore, the high-weight subjects from both conditioning groups suppressed more than their low-weight counterparts in the presence of the CS.

Passive avoidance learning in rats, mice, gerbils, and hamsters

The acquisition of a passive avoidance response to electric shock was studied in hooded and albino rats, albino mice, gerbils, and hamsters. Rats acquired this response more rapidly than any of the other species. There were no differences in rate of acquisition between the two strains of rats or among the other three species. These results indicate that species-specific defense reactions may interact with the particular behavioral task in which the organism is studied.

Reward Schedules and Instrumental Conditioning in Normal and Retarded Children

The performances of retarded and normal children, matched for MA, were compared in a simple instrumental conditioning situation under conditions of continuous and alternating partial reward. Acquisition and extinction series were administered in an attempt to discern the relative effects of differential cues and schedules of reinforcement. Speed of response was used as a measure of learning. A significant difference between speeds on reinforced and nonreinforced trials was demonstrated for both normals and retardates. Although absolute response speeds of retardates were significantly slower than those of normals, there appeared to be no difference in rate of acquisition. Both groups learned quickly to anticipate the reward schedule, and there was no difference in their rates of extinction.