Formation of tone-US associations does not interfere with the formation of context-US associations in pigeons

In four experiments we investigated whether signaled and unsignaled US presentations resulted in differential context conditioning. Experiments 1 and 2 showed that the presence of a tone during grain presentation facilitated the formation of tone-food associations in pigeons. Experiment 2 also showed that the acquisition of associative value by the tone did not diminish associations between context and the unconditioned stimulus (US). Experiment 3 showed that signaled USs did not interfere with the acquisition of context-US associations, and Experiment 4 showed that even when the signal was extensively pretrained, context-US associations could not be blocked. The results of these experiments are inconsistent with conditioning models that require competition between cues and contexts for associative value.     

The impact of familiarization strategies on the missing-letter effect

When reading a text and searching for a target letter, readers make more omissions of the target letter if it is embedded in frequent function words than if it is in rare content words. While word frequency effects are consistently found, few studies have examined the impacts of passage familiarity on the missing-letter effect and studies that have present conflicting evidence. The present study examines the effects of passage familiarity, as well as the impacts of passage familiarization strategy promoting surface or deep encoding, on the missing-letter effect. Participants were familiarized with a passage by retyping a text, replacing all common nouns with synonyms, or generating a text on the same topic as that of the original text, and then completed a letter search task on the familiar passage as well as an unfamiliar passage. In Experiment 1, when both familiar and unfamiliar passages use the same words, results revealed fewer omissions for the retyping and synonyms conditions. However, in Experiment 2, when different words are used in both types of texts, no effect of familiarization strategy was observed. Furthermore, the missing-letter effect is maintained in all conditions, adding support to the robustness of the effect regardless of familiarity with the text.     

Implicit bias in impression formation: associations influence the construal of individuating information

The present research investigated the influence of group‐related evaluative associations on the process of impression formation. In particular, we expected the impact of a target's category membership on the construal of ambiguous behaviour to be moderated by perceivers' evaluative associations related to the target category. Associative strength was further expected to have an indirect effect on dispositional inference, mediated by its impact on behaviour identification. Results support both of these assumptions. Moreover, the influence of evaluative associations on impression formation was not moderated by perceivers' motivation to control prejudiced reactions. Rather, motivation to control moderated only the relation between evaluative associations and the explicit endorsement of prejudiced beliefs about the target group in general, such that explicit prejudice endorsement was correlated with evaluative associations only for perceivers low, but not for those high in motivation to control. Implications for prejudice control are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Modulation of brain activity during phonological familiarization

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri. At the same time, interaction analysis showed that the magnitude of decrease of activity in bilateral posterior temporal lobe was significantly smaller for LF nonwords, relative to words and HF nonwords. Decrease of activity in this area also correlated with the size of behavioral familiarization effects for LF nonwords. The results show that the posterior superior temporal gyrus plays a fundamental role during phonological learning. Its relationship to sublexical and lexical phonological processing as well as to phonological short-term memory is discussed.     

Associative symmetry versus independent associations in the memory for object-location associations

The formation of associations between objects and locations is a vital aspect of episodic memory. More specifically, remembering the location where one experienced an object and, vice versa, the object one encountered at a specific location are both important elements for the memory of an event. Whether episodic associations are holistic representations of individual components or whether there are unidirectional, separately modifiable connections between them has been investigated nearly exclusively using verbal stimuli. A preliminary conclusion concerning this controversy is that verbal associations are, at least, highly correlated (M. J. Kahana, 2002). This theoretical debate, which in the past has undergone a major empirical effort, is still of relevance for the concurrent global matching models of associative memory (S. E. Clark & S. D. Gronlund, 1996). The authors used variations of a novel object-location learning paradigm to complement the accumulated evidence regarding the nature of episodic associations.     

Slipping during side-step cutting: Anticipatory effects and familiarization

The aim of the present study was to verify whether the expectation of perturbations while performing side-step cutting manoeuvres influences lower limb EMG activity, heel kinematics and ground reaction forces. Eighteen healthy men performed two sets of 90° side-step cutting manoeuvres. In the first set, 10 unperturbed trials (Base) were performed while stepping over a moveable force platform. In the second set, subjects were informed about the random possibility of perturbations to balance throughout 32 trials, of which eight were perturbed (Pert, 10 cm translation triggered at initial contact), and the others were “catch” trials (Catch). Center of mass velocity (CoM_VEL), heel acceleration (H_AC), ground reaction forces (GRF) and surface electromyography (EMG) from lower limb and trunk muscles were recorded for each trial. Surface EMG was analyzed prior to initial contact (PRE), during load acceptance (LA) and propulsion (PRP) periods of the stance phase. In addition, hamstrings-quadriceps co-contraction ratios (CCR) were calculated for these time-windows. The results showed no changes in CoM_VEL, H_AC, peak GRF and surface EMG PRE among conditions. However, during LA, there were increases in tibialis anterior EMG (30–50%) concomitant to reduced EMG for quadriceps muscles, gluteus and rectus abdominis for Catch and Pert conditions (15–40%). In addition, quadriceps EMG was still reduced during PRP (p < .05). Consequently, CCR was greater for Catch and Pert in comparison to Base (p < .05). These results suggest that there is modulation of muscle activity towards anticipating potential instability in the lower limb joints and assure safety to complete the task.     

Environmental familiarization in rats: differential effects of acute and chronic nicotine

If an environment is familiar, rats will interact more with a novel object than if the environment is unfamiliar. In two experiments we used this behavioral tendency to assess the effects of nicotine on environmental familiarization (i.e., an elevated platform). As expected, rats given 2 min of exposure to the platform on 2 consecutive days (familiarization phase) interacted more with a novel object in a subsequent test than rats that had not experienced the platform until the test day. During the familiarization phase acute pretreatment with nicotine (0.6 and 1.8 mg/kg, subcutaneous) 10 min before platform exposure interfered with familiarization processes, as measured by object interaction on the drug-free test day. Behavioral measures of activity (e.g., turning and midline crosses) eliminated an account based on nicotine-induced motor impairment. Furthermore, this effect of acute nicotine on familiarization was not due to nonspecific effects of nicotine. Controls that received equivalent nicotine exposure temporally separated from platform exposure interacted more with the novel object than similarly treated controls that were unfamiliar with the platform on the test day. Interestingly, rats treated once daily with 0.6 mg/kg nicotine for 14 days before the familiarization phase (chronic condition) did not show a decrease in environmental familiarity. This dissociation extends a growing literature finding that the behavioral and neurobiological effects of nicotine differ, in part, after acute and chronic exposure. Indeed, acute nicotine (0. 2, 0.6, and 1.2 mg/kg) in the present report consistently decreased the amount of time spent with one paw on the edge of the platform; chronic nicotine did not affect this behavior.     

Cross-accent intelligibility of speech in noise: Long-term familiarity and short-term familiarization

Listeners must cope with a great deal of variability in the speech signal, and thus theories of speech perception must also account for variability, which comes from a number of sources, including variation between accents. It is well known that there is a processing cost when listening to speech in an accent other than one's own, but recent work has suggested that this cost is reduced when listening to a familiar accent widely represented in the media, and/or when short amounts of exposure to an accent are provided. Little is known, however, about how these factors (long-term familiarity and short-term familiarization with an accent) interact. The current study tested this interaction by playing listeners difficult-to-segment sentences in noise, before and after a familiarization period where the same sentences were heard in the clear, allowing us to manipulate short-term familiarization. Listeners were speakers of either Glasgow English or Standard Southern British English, and they listened to speech in either their own or the other accent, thereby allowing us to manipulate long-term familiarity. Results suggest that both long-term familiarity and short-term familiarization mitigate the perceptual processing costs of listening to an accent that is not one's own, but seem not to compensate for them entirely, even when the accent is widely heard in the media.     

Light reinforcement in the rat: The effects of continuous and discontinuous periods of apparatus familiarization

The effects of continuous and discontinuous periods of apparatus familiarization on light reinforcement in rats were examined. A previous finding that the light reinforcement effect is greater with longer pretest periods in the dark box was confirmed by comparing 270 min and 30 min periods in the box prior to testing 24 h later. A discontinuous period of 9 daily 30 min sessions, however, produced a bigger effect than the 270 min continuous period. It was concluded that the degree of familiarization with the apparatus is a more important factor than length of time per se in the dark in determining the effectiveness of light as a reinforcer.     

Associating unseen events: semantically mediated formation of episodic associations

In prior work, we developed a computational model of how episodic associations between words are formed. Simulating associative learning, the model indicated that strongly associated semantically unrelated words facilitate the episodic association of other exemplars included in their semantic neighborhoods. This prediction was supported empirically by the present study. First, the incidental formation of strong associations between unrelated words, such as dog and table, improved cued recall of weak associations formed incidentally between semantic neighbors, like cat and chair. Second, deciding that two words were semantically unrelated was facilitated by forming strong associations between other words in their respective semantic neighborhoods, even if the tested pair was not presented at study. Together with the computational model, the present results demonstrate that forming episodic associations between words can implicitly mediate the association of other exemplars from the same semantic categories and reveal a mechanism by which the semantic system contributes to the formation of new episodic associations.     

Maximum isokinetic familiarization of the knee: Implication on bilateral assessment

PurposeFamiliarization is necessary for an accurate strength assessment as it reduces confounding factors such as learning and training effects. However, the number of contractions required for familiarization and whether cross-limb transfer during familiarization could affect bilateral assessment are unknown. This study aimed at identifying the number of maximum contractions required for isokinetic knee extension and flexion familiarization in both dominant (D) and non-dominant limb (ND).MethodsTwenty-eight right-limb dominant males (age: 22.64 ± 2.60 years, BMI: 23.82 ± 2.85 kg/m²) performed a total of 6 sets (each consisted of 5 continuous maximum contractions) at 60^o/s for each limb.ResultsThe number of sets required for familiarization is determined when the average peak torque achieved stabilization from the series of contractions of each limb. For knee extension, 3 sets (15 contractions) were required for familiarization, whereas 2 sets (10 contractions) for knee flexion in both limbs. Interestingly, for knee extension in ND, the number of sets required for familiarization was reduced to 2 following contralateral contractions in D, however, for knee extension in D, there was no difference in the number of sets required for familiarization following contralateral contractions in ND. While for knee flexion, no cross-limb transfer was observed. These observations suggest the presence of cross-limb transfer from D to ND during familiarization which implies the involvement of the central nervous system.ConclusionsPractically, familiarization for bilateral isokinetic strength assessment for knee extension and flexion at 60^o/s should begin with the dominant limb for 3 sets to obtain accurate and reliable measurements.