Combining image degradations in a recognition task

Six experiments are reported that investigate the effect on form recognition performance of combining three kinds of stimulus degradations: local area averaging of intensities, low-pass spatial frequency filtering, and random dot visual interference. The effects are shown to be more complicated than previously reported in simple demonstrations. The complexity of the results suggests that models based on single stimulus attributes such as energy or spatial frequency spectrum probably cannot account for the data. Eclectic theories that invoke combinations of redundant processes may be necessary for describing visual recognition phenomena, even within the limited domain examined in this study.     

Inhibition of return in a discrimination task

Inhibition of return (IOR) refers to a bias against returning visual attention to a location that has been recently attended. Although IOR has been demonstrated in a wide range of detection tasks, it has not been reliably shown in discrimination tasks. The results of the present experiment, in which eye movement responses and a cue-target procedure were used, indicate that IOR can exist in a discrimination task. Moreover, the results indicate that the amount of IOR in the discrimination task was approximately equal to that found in the detection task. The results suggest that IOR will be obtained in a discrimination task if the prior allocation of attention does not yield any useful information concerning the forthcoming discrimination judgment.     

The effect of reinforcement probability on time discrimination in the midsession reversal task

We examined how biasing time perception affects choice in a midsession reversal task. Given a simultaneous discrimination between stimuli S1 and S2, with choices of S1 reinforced during the first, but not the second half of the trials, and choices of S2 reinforced during the second, but not the first half of the trials, pigeons show anticipation errors (premature choices of S2) and perseveration errors (belated choices of S1). This suggests that choice depends on timing processes, on predicting when the contingency reverses based on session duration. We exposed 7 pigeons to a midsession reversal task and manipulated the reinforcement rate on each half of the session. Compared to equal reinforcement rates on both halves of the session, when the reinforcement rate on the first half was lower than on the second half, performance showed more anticipation and less perseveration errors, and when the reinforcement rate on the first half was higher than on the second half, performance showed a remarkable reduction of both types of errors. These results suggest that choice depends on both time into the session and the outcome of previous trials. They also challenge current models of timing to integrate local effects.     

The use of olfactory cues in solving a visual discrimination task

Albino rats, trained in a miniaturized WGTA, were found to learn an olfactory discrimination despite the fact that visual cues were relevant and obvious. The results provide a further warning against the use of macrosmatic animals in visual discrimination tasks in which olfactory cues may be relevant.     

Joint stimulus control in a temporal discrimination task

The ability to identify stimuli that signal important events is fundamental for an organism to adapt to its environment. In the present paper, we investigated how more than one stimulus could be used jointly to learn a temporal discrimination task. Ten pigeons were exposed to a symbolic matching-to-sample procedure with three durations as samples (2, 6, and 18 s of keylight) and two colors as comparisons (red and green hues). A 30-s intertrial interval (ITI), illuminated with a houselight, separated the trials. Both the houselight and the sample keylight could control responding, so two tests were run to assess how these stimuli influenced choice. In the no-sample test, the keylight was not presented; in the dark-ITI test, the houselight was not illuminated. Results suggest that both houselight and keylight controlled choice, and with the exception of one animal, the more a pigeon relied on one of these stimuli, the less it appeared to rely on the other.     

Quantity discrimination in a spontaneous task in a poison frog

Animal Cognition - The use of quantitative information underlies a range of animal behaviors. There are thought to be two parallel systems for judging quantity: a precise representation of small...     

The role of the amygdala in facial emotional expression during a discrimination task

A total of 50 patients with temporal lobe epilepsy with unilateral resection of the hippocampus and the amygdala were studied: --27 with left lobectomy (LTL group) and 23 with right lobectomy (RTL group)--; and 28 healthy control participants (HC group). The task consisted of identifying the dissimilar photograph from a group of photographs of the same face. The difference could correspond to the identity of the model or the facial expression (happiness, anger, sadness and fear). The results showed that when the difference in the photograph resided in the identity of the model, the RTL group made more mistakes than the HC group. When the facial expression was the distinguishing feature, mean response latency was longer in the LTL group than in the HC group. Comparison of the emotions revealed that the greatest differences were obtained with the fear expression, in all three participant groups. The dissociation of neural circuits responsible for processing facial expressions is discussed and, especially, the role of the left amygdala to discriminate between facial expressions.     

Constraints on strategy construction in a speeded discrimination task

In three experiments, subjects reported the identity of a word (above or below) that appeared above or below a fixation point. On some trials, a cue presented 100, 200, 400, 600, 800, or 1,000 msec before the word indicated the relation between position and identity (i.e., whether the dimensions were compatible, e.g., above/above and below/below, or conflicted, e.g., above/below and below/above). On the other trials, the cue was withheld (Experiment 2) or it bore no information about the relation between dimensions (Experiment 1 and 3). In each experiment, the cue reduced reaction time below the level of no-cue or neutral-cue controls, indicating strategic use of the relation between dimensions. Experiments 1 and 2 manipulated the number of potential cues that could occur in a block. A stronger cuing effect was found when one cue could occur (Experiment 2) than when two cues could occur (Experiment 1). Experiment 3 manipulated practice; it revealed that with practice the cuing effect reached asymptote at shorter delays. The asymptote itself did not change. Experiment 4 showed that cue-delay effects were independent of warning interval (warning interval and cue delay confounded in Experiment 1, 2, and 3). The experiments demonstrate construction and utilization of strategies; they show that construction is sensitive to constraints imposed by the subject's goals and abilities and by the structure of the task environment.     

An experimental investigation of the effect of worry on responses to a discrimination learning task

The current study examined the impact of both the tendency to worry (trait worry) and the process of worry (state worry) on subsequent behavioral responding in a schedule discrimination learning task. High and low trait worriers were randomly assigned to a state worry or relaxation incubation condition and completed a test of executive functioning and a dual contingency learning task that utilized neutral discriminative cues over the course of 2 contingency phases. Although state and trait worry did not impact executive functioning, the state worry condition was associated with diminished sensitivity to learning task contingencies over the course of the first contingency learning trials in comparison to the relaxation condition. This relationship was unique to the state worry condition above and beyond shared variance with subjective anxiety level. Results suggest that state worry may lead to a decrement in selective behavioral responding to neutral discriminative cues in the environment. The findings suggest that the process of worry may lead to less adaptive responding to neutral cues and interfere with adaptive behaviors, which may thereby contribute to and maintain anxiety.     

Temporal expectancy modulates inhibition of return in a discrimination task

This research examined the influence of cue temporal predictability on inhibition of return (IOR) in a discrimination task. In exogenous attention experiments, the cue that summons attention is noninformative as to where the target will appear. However, it is predictive as to when it will appear. In previous work, it was demonstrated that temporal predictability does not influence IOR in detection tasks. In this work, it is shown that IOR is influenced by temporal predictability in discrimination tasks. Predictability was manipulated by using three stimulus onset asynchrony distributions: nonaging, aging, and accelerated aging. IOR was found when the cue predicted target appearance and was modulated by temporal information. In the nonaging distribution (in which the cue did not predict target appearance), there was no IOR.     

Nimodipine alters acquisition of a visual discrimination task in chicks

Chicks 5 days old received intraperitoneal injections of nimodipine 30 min before training on either a visual discrimination task (0, 0.5, 1.0, or 5.0 mg/kg) or a test of separation-induced distress vocalizations (0, 0.5, or 2.5 mg/kg). Chicks receiving 1.0 mg/kg nimodipine made significantly fewer visual discrimination errors than vehicle controls by trials 41-60, but did not differ from controls 24 h later. Chicks in the 5 mg/kg group made significantly more errors when compared to controls both during acquisition of the task and during retention. Nimodipine did not alter separation-induced distress vocalizations at any of the doses tested, suggesting that nimodipine's effects on learning cannot be attributed to a reduction in separation distress. These data indicate that nimodipine's facilitation of learning in young subjects is dose dependent, but nimodipine failed to enhance retention.     

Attenuated audiovisual integration in middle-aged adults in a discrimination task

Numerous studies have focused on the diversity of audiovisual integration between younger and older adults. However, consecutive trends in audiovisual integration throughout life are still unclear. In the present study, to clarify audiovisual integration characteristics in middle-aged adults, we instructed younger and middle-aged adults to conduct an auditory/visual stimuli discrimination experiment. Randomized streams of unimodal auditory (A), unimodal visual (V) or audiovisual stimuli were presented on the left or right hemispace of the central fixation point, and subjects were instructed to respond to the target stimuli rapidly and accurately. Our results demonstrated that the responses of middle-aged adults to all unimodal and bimodal stimuli were significantly slower than those of younger adults (p < 0.05). Audiovisual integration was markedly delayed (onset time 360 ms) and weaker (peak 3.97%) in middle-aged adults than in younger adults (onset time 260 ms, peak 11.86%). The results suggested that audiovisual integration was attenuated in middle-aged adults and further confirmed age-related decline in information processing.     

Reaction times of pigeons on a wavelength discrimination task

After extensive pretraining, three pigeons were exposed in 2-second trials to a random series of 14 light wavelengths, ranging in one nanometer (nm) steps from 575 nanometers to 589 nanometers. Responses to one of the wavelengths, 582 nanometers, were intermittently reinforced. The relative frequency of response approached 1.0 at 582 nanometers, and decreased with progressively higher and lower wavelengths. Reaction times shorter than about 0.2 second occurred with a low frequency that was largely independent of wavelength. Wavelength controlled the frequency of longer reaction times, but did not affect the distribution of these reaction times. Consequently, receiver-operating characteristic curves constructed by using reaction time as a rating measure did not conform to the signal-detection model, in contrast to such conformity when response rate is used in a similar way. The data suggest that stimulus onset as such triggers early response emission with some small probability; the probability of responses with longer latency is controlled by wavelength, but their time of emission is controlled by some independent process.     

Within-modality and cross-modality attentional blinks in a simple discrimination task

Following up on studies of the "attentional blink," we studied interference between successive target stimuli in visual and auditory modalities. In each experiment, stimuli were two tones and four dots, simultaneously presented for 1,800 msec. Targets were brief intensity changes in either a tone or a dot. Subjects gave unspeeded responses. In four experiments, our results showed interference between targets in the same modality, but not across modalities. We conclude that, under our experimental conditions, restrictions in concurrent target identification are largely modality specific.     

Behaviors observed during S- in a simple discrimination learning task

Key pecking of pigeons was reinforced with food in the presence of a horizontal line and never reinforced in the presence of a vertical line. Highly stereotyped behaviors, as well as key pecking, were observed and recorded in the presence of both stimuli. Results showed that a high proportion of time spent in the presence of the horizontal line was occupied by key pecking, a high proportion of time in the presence of the vertical line was occupied by stereotyped nonkey-pecking behaviors, and intermediate proportions of time spent in the presence of intermediate stimuli were occupied by each class of behavior during generalization tests. Similar running rates (number of key pecks divided by observed key-pecking time) were obtained in the presence of all stimuli, indicating that changes in time rather than tempo accounted for the changes in overall rates of key pecking. An exception occurred in responding to the horizontal line as differential performance was developing. In addition to an increase in time spent key pecking, increased running rates occurred in seven of eight birds, suggesting that both time allocation and tempo play a role in behavioral contrast of overall rates of key pecking.