Endogenous modulation of compatibility effects: an Investigation into the temporal dynamics

Compatibility effects (CEs) arise when multiple stimuli fall within the visual field, providing an indication of stimulus processing. Previous research demonstrated that exogenous factors (e.g., luminance) influence the magnitude of CEs and their time course. The current research investigated the influence of endogenous factors. We used a flanker paradigm with a variable temporal delay (SOA) between a flanker and a subsequent central stimulus appearing. To manipulate endogenous factors, we required responses to the flanker on either half or all of the trials. The results indicate that increasing the task relevance of the flanker strengthened the initial positive CE (measured at short SOAs), consistent with past findings related to exogenous factors. However, at longer SOAs, the CE did not reverse into a negative CE, which stands against findings related to exogenous factors. These results indicate that CEs are subject to endogenous modulation, but the temporal dynamics do not mimic exogenous modulation.     

Evaluation of the accuracy,reliability, efficiency,and acceptability of fast forwarding to score problem behavior

Technological advances have allowed professionals to obtain extended recordings of caregiver–client interactions in natural settings, but scoring recorded video at normal speed to identify instances of low‐rate problem behavior is impractical in terms of scoring time. Fast forwarding is a continuous measurement system in which all seconds of an observation are viewed at a speed faster than normal. In Study 1, we evaluated whether three groups of five observers could discriminate problem behavior at three fast‐forwarding speeds across 10‐min observations. We analyzed the efficiency of using fast forwarding compared to continuous scoring, and interobserver agreement across the fast‐forwarding speeds. In Study 2, we compared the accuracy, efficiency, and social acceptability of fast forwarding (3.5x) and momentary time sampling (3.5 s) across 90‐min observations. Results support the use of 3.5x fast forwarding as a viable measurement system of improving the practicality of scoring problem behavior from video.     

Strategic control over saccadic eye movements: studies of the fixation offset effect

We studied the strategic (presumably cortical) control of ocular fixation in experiments that measured the fixation offset effect (FOE) while manipulating readiness to make reflexive or voluntary eye movements. The visual grasp reflex, which generates reflexive saccades to peripheral visual signals, reflects an opponent process in the superior colliculus (SC) between fixation cells at the rostral pole, whose activity helps maintain ocular position and increases when a stimulus is present at fixation, and movement cells, which generate saccades and are inhibited by rostral fixation neurons. Voluntary eye movements are controlled by movement and fixation cells in the frontal eye field (FEF). The FOE--a decrease in saccade latency when the fixation stimulus is extinguished--has been shown to reflect activity in the collicular eye movement circuitry and also to have an activity correlate in the FEF. Our manipulation of preparatory set to make reflexive or voluntary eye movements showed that when reflexive saccades were frequent and voluntary saccades were infrequent, the FOE was attenuated only for reflexive saccades. When voluntary saccades were frequent and reflexive saccades were infrequent, the FOE was attenuated only for voluntary saccades. We conclude that cortical processes related to task strategy are able to decrease fixation neuron activity even in the presence of a fixation stimulus, resulting in a smaller FOE. The dissociation in the effects of a fixation stimulus on reflexive and voluntary saccade latencies under the same strategic set suggests that the FOEs for these two types of eye movements may reflect a change in cellular activity in different neural structures, perhaps in the SC for reflexive saccades and in the FEF for voluntary saccades.     

Shifts in the psychometric function and their implications for models of timing

This study examined how two models of timing, scalar expectancy theory (SET) and learning to time (LeT), conceptualize the learning process in temporal tasks, and then reports two experiments to test these conceptualizations. Pigeons responded on a two-alternative free-operant psychophysical procedure in which responses on the left key were reinforceable during the first two, but not the last two, quarters of a 60-s trial, and responses on the right key were reinforceable during the last two, but not the first two, quarters of the trial. In Experiment 1 three groups of birds experienced a difference in reinforcement rates between the two keys only at the end segments of the trial (i.e., between the first and fourth quarters), only around the middle segments of the trial (i.e., between the second and third quarters), or in both end and middle segments. In Condition 1 the difference in reinforcement rate favored the left key; in Condition 2 it favored the right key. When the reinforcement rates differed in the end segments of the trial, the psychometric function--the proportion of right responses across the trial--did not shift across conditions; when it occurred around the middle of the trial or in both end and middle segments, the psychometric function shifted across conditions. Experiment 2 showed that the psychometric function shifts even when the overall reinforcement rate for the two keys is equal, provided the rates differ around the middle of the trial. This pattern of shifts of the psychometric function is inconsistent with SET. In contrast, LeT provided a good quantitative fit to the data.     

Self-reported psychosocial factors among in vitro fertilization patients interviewed alone or with the partner

The purpose of this study was to compare the sociodemographic and psychosocial characteristics reported by female in vitro fertilization (IVF) patients interviewed alone or with the partner in heterosexual couples. During 12 months (2011–2012), all patients undergoing IVF or intracytoplasmic sperm injection at one public reproductive medicine unit, in Portugal, were interviewed on the day of the diagnosis of pregnancy, being recruited 221 women interviewed with the partner and 92 interviewed alone. Interviewers collected data on sociodemographic and obstetric characteristics; and anxiety, depression, social support and partner relationship were collected by self-administered questionnaires. χ² test was used to assess the independent association between the categorical variables and being interviewed alone or with the partner. For continuous variables, mean or median differences were compared by the t-test or the Mann–Whitney test, according to data distribution. No statistically significant differences were found in the self-reporting of depression, anxiety, social support and partner relationship or in sociodemographic and obstetric characteristics between women interviewed alone or with the partner. Although women interviewed alone were older and more frequently had children than women interviewed with the partner, no significant associations were observed. Thus, having a male partner present in the research setting during a self-administered questionnaire seems not to influence women’s responses to psychosocial measures. Other outcomes and settings need to be evaluated to support evidence-based guidelines for research on infertility.     

Temporal generalization gradients following an interdimensional discrimination protocol

We investigated the effects of interdimensional discrimination training in the temporal generalization gradient. In a matching-to-sample task, pigeons learned to choose key S after a T–s houselight sample and key NS in the absence of the houselight sample. For one group of pigeons, T?=?20?s; for another, T?=?10?s. Subsequently, houselight duration was varied to obtain temporal generalization gradients. Results showed that (a) proportion S increased as houselight duration ranged from 0?s to T?s and then remained high for houselight durations longer than T; (b) the gradients were well described by negative-exponential functions; (c) these non-flat gradients were present from the beginning of testing, and; (d) the average gradients obtained with T?=?20?s and T?=?10?s overlapped when plotted in relative time. We conclude that temporal control does not require explicit discrimination training along the temporal dimension, and that temporal generalization gradients obtained with an interdimensional protocol show the scalar property of timing. We discuss how these findings challenge current models of timing.     

A new variable interval schedule with constant hazard rate and finite time range

We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function.     

The differentiation of response numerosities in the pigeon

Two experiments examined how pigeons differentiate response patterns along the dimension of number. In Experiment 1, 5 pigeons received food after pecking the left key at least N times and then switching to the right key (Mechner's Fixed Consecutive Number schedule). Parameter N varied across conditions from 4 to 32. Results showed that run length on the left key followed a normal distribution whose mean and standard deviation increased linearly with N; the coefficient of variation approached a constant value (the scalar property). In Experiment 2, 4 pigeons received food with probability p for pecking the left key exactly four times and then switching. If that did not happen, the pigeons still could receive food by returning to the left key and pecking it for a total of at least 16 times and then switching. Parameter p varied across conditions from 1.0 to .25. Results showed that when p= 1.0 or p=.5, pigeons learned two response numerosities within the same condition. When p=.25, each pigeon adapted to the schedule differently. Two of them emitted first runs well described by a mixture of two normal distributions, one with mean close to 4 and the other with mean close to 16 pecks. A mathematical model for the differentiation of response numerosity in Fixed Consecutive Number schedules is proposed.     

Testing the Δ-∑ hypothesis in the suboptimal choice task: Same delta with different probabilities of reinforcement

In a concurrent-chain procedure, pigeons choose between 2 initial-link stimuli; one is followed by terminal link stimuli that signal reliably whether food will be delivered after a delay; the other is followed by terminal link stimuli that do not signal whether food will be delivered after the delay. Pigeons prefer the former alternative even when it yields a lower overall probability of food. Recently, we proposed the Delta-Sigma (∆-∑) hypothesis to explain the effect: Preference depends on the difference (∆) between the reinforcement probabilities associated with the terminal link stimuli, and the overall probability of reinforcement (∑) associated with the alternative. The hypothesis predicts that, for constant ∑, animals should prefer alternatives with greater ∆ values regardless of the specific probabilities of reinforcement that determine ∆. In 2 experiments, we tested this prediction by comparing a ∆ = .5 against a ∆ = 0 alternative, with the former obtained with different pairs of reinforcement probabilities across conditions. The results supported the hypothesis when the 2 probabilities defining ∆ were significantly greater than 0, but not when one of them was close to 0. The results challenge our theoretical accounts of suboptimal choice and the variables considered to determine pigeons’ preference.     

Covert orienting to the locations of targets and distractors: Effects on response channel activation in a flanker task

The role of covert orienting of attention in response channel activation was examined using the flanker interference and precueing paradigms. Four experiments assessed the influence of distractors on the discrimination of a target colour patch under cueing conditions (three with non-informative, exogenous cues and one with informative, endogenous cues) that modulated attention at the flanker or target locations. Across all of the experiments, the amount of interference generated by the distractors was not modulated by the facilitation and inhibition of return induced by spatial attention precues. These results are consistent with previous reports of patients with neglect, which demonstrated that flanker interference proceeds at unattended locations (Audet, Bub, & Lecours, 1991; Cohen, Ivry, Rafal, & Kohn, 1995), and they suggest that response channel activation can occur independently from spatial attention.