Simultaneous Discrimination Task Research Articles

Assessing the motivational value of infant video clips on chimpanzees through discrimination learning task.

The motivational value of visual infant stimuli in humans is considered to encourage parental behavior. To explore the evolutionary roots of this preference for infants, we examined the reward value of conspecific infant videos compared to adult ones in nine chimpanzees. We employed a novel approach, a simultaneous discrimination task with differential sensory reinforcement. In Experiments 1 and 2, we tested if watching conspecific infant videos is more rewarding than watching adult ones. Participants were required to discriminate between two visual stimuli by a touch panel task. In video reward trials, a video clip featuring a chimpanzee infant followed a correct choice, while one featuring an adult followed an incorrect choice. However, the percentage of correct choices did not significantly differ from chance except in one chimpanzee, indicating that chimpanzees did not exhibit a preference for watching infant videos over those of adult. In Experiment 3, we tested if chimpanzees prefer conspecific videos over a blank screen; however, we did not find evidence either at a group level. These results suggest that the incentive salience of infant stimuli may not be universally compelling across species. Additionally, we discuss the limitations of the task using sensory reinforcement.

Does the type of task affect prey discrimination learning in avian predators?

AbstractWhen learning to discriminate between palatable and unpalatable prey, predators may encounter the prey either simultaneously or in a sequence. The two types of discrimination tasks, which are frequently used in experiments focused on aposematism and mimicry, may considerably differ in difficulty, as they differ in the information available to predators during individual encounters with prey. Surprisingly, there are very few studies directly comparing the performance of predators between sequential and simultaneous discrimination tasks using otherwise identical experimental design, the same predators and prey. We tested the effect of the type of discrimination task on the effectiveness of discrimination learning in adult and juvenile great tits (Parus major). Birds were trained to discriminate between palatable and unpalatable artificial prey items baited with mealworms soaked either in water or quinine. Prey shape, colours and patterns were derived from real shield bug species. We compared the performance of birds tested with two discriminative cues, colour and pattern, using three discrimination tasks: (1) sequential—alternating presentation of one palatable and one unpalatable prey item, (2) two‐choice—simultaneous presentation of one palatable and one unpalatable prey item and (3) multiple‐choice—simultaneous presentation of multiple palatable and unpalatable prey items. Colour was a more effective discriminative cue than pattern for both adult and juvenile birds. Adults performed better than juveniles regardless of task. The birds performed equally well in the sequential and two‐choice tasks, but their performance in the multiple‐choice task was worse than in the other two tasks. However, these differences were only present when the birds used the pattern as a discriminative cue. The birds tested with colour, a more salient cue, performed equally well in all three tasks. Type of discrimination task may therefore affect the learning performance of predators, but the effect also depends on the saliency of a particular discriminative cue.

Vigilance end-spurt patterns in event-related potentials

The end-spurt effect, where performance declines with time-on-task and then increases toward the end of a task, has garnered little attention in the vigilance literature. Researchers have suggested the performance enhancement is due to increased motivation or arousal with knowledge of the end of the vigil. However, recent examination of neural signature patterns during a simultaneous discrimination task, where task length was unknown, provided preliminary support that the end-spurt reflects pacing of resources. The current effort expands this previous work to an additional simultaneous task and to a successive discrimination task across two sessions, one where task length was not known and one where task length was known. Twenty-eight (Study 1) and a separate 24 (Study 2) participants completed a Simultaneous Radar task (Study 1) in one session and Simultaneous and Successive Lines tasks (Study 2) across two sessions while neural data was collected. Several event-related potentials exhibited non-monotonic patterns during the vigilance tasks, in some cases reflecting end-spurt patterns, but more commonly reflecting higher-order polynomial patterns. These patterns were more prevalent in anterior regions as opposed to posterior regions. Of note, the N1 anterior exhibited consistent general patterns across all the vigilance tasks and across sessions. Importantly, even when participants had knowledge of session length, some ERPs still exhibited higher-order polynomial trends, suggesting pacing rather than an end-spurt from motivation or arousal as the vigil ends. These insights can help inform predictive modeling of vigilance performance and the implementation of mitigation efforts to allay the vigilance decrement.

Measurement of the exploration–exploitation response of dogs through a concurrent visual discrimination task

In many species, the allocation of exploration and exploitation responses to environmental stimuli is important for survival. In this exploratory study, we determined whether dogs (Canis familiaris) explored novel stimuli in a visual discrimination task using food reinforcers. Initially, the dogs were trained with two pairs of simultaneous visual discrimination tasks. Having achieved the learning criterion, the dogs were presented with a pair of stimuli including a novel stimulus and a previously reinforced stimulus in the probe trials (familiar stimulus). Dogs were reinforced by 50% for novel stimuli and 100% for familiar stimuli. The proportions of responses to novel and familiar stimuli in the probe trials were considered to reflect the propensity for exploration and exploitation, respectively. The five dogs tested selected the novel stimulus more frequently (in 22 of the 30 probe trials; binomial test, P = 0.016). Therefore, dogs prefer novel stimuli over familiar ones, suggesting that this species, which is less neophobic than wolves (Canis lupus), would likely allocate more responses to exploration. Comparisons among breeds or with wolves are warranted in future studies.

Effects of Inaccurate Feedback on Simultaneous Amplitude and Frequency Discrimination Tasks

Humans frequently engage in tasks with the intention of performing well. Many previous studies have explored feedback as a tool to improve this task performance, concluding that feedback improves task performance, but only when coupled with a task performance goal. However, there is no clear consensus on how feedback without goalsetting impacts task performance. This paper aims to investigate feedback’s impact on task performance from a new angle by determining how incorrect feedback affects task performance. Through this investigation, we explored the participant thought process that plays into how the participant uses feedback. This has several implications, for example, in regard to malingering, in which people purposefully provide incorrect feedback for personal gain. To conduct this study, we instructed participants to complete simultaneous tactile discrimination tasks on which they received correct or incorrect feedback. Our results showed a significant difference in task performance between correct and incorrect feedback, and this difference increased for a harder task. Additionally, our results demonstrated that several participants receiving incorrect feedback had longer response times, indicating that they realized they were receiving incorrect feedback. Overall, this study sheds light on how feedback can be used to manipulate task performance.

The effects of physical luminance on colour discrimination in dogs: A cautionary tale

Due to the composition of the cone photoreceptors in the retina of dogs, it has been proposed they might demonstrate human-like red/green colour blindness. However, some assessments have shown that dogs may still be able to distinguish between red and green. This suggests that dogs may be differentiating between the two colours on the basis of their brightness. To further explore this issue, the present investigation tested dogs’ abilities to differentiate between two colours at different physical luminance levels. Seven dogs were trained on a simultaneous size discrimination task in which two circles were presented on a monitor. The colours of the circles were then varied such that dogs would choose one stimulus if they could discriminate between two colours and a different stimulus if they could not. Four experiments were conducted. The first presented dogs with yellow, blue, green, and red stimuli at their maximum red, green, and blue (RGB) values. All seven dogs were equally proficient at discriminating between red and green, yellow and blue, and black and white stimuli as no difference in performance was observed (p = 0.52). In Experiments 2–4, the four colours were presented with equal physical luminance across three different intensities. All seven dogs successfully discriminated between all four colours when the colours were isoluminant at 34.6 cd/m2 as no differences in performance was observed (p = 0.10). When presented with isoluminant stimuli at 41.9 cd/m2, a difference was observed between conditions, with the dogs failing to detect red stimuli presented on a green background compared to the achromatic controls (p = 0.03). When presented with stimuli at 49.3 cd/m2, a difference was again observed between conditions, but this time the dogs were unable to detect blue stimuli presented on a yellow background compared to the achromatic controls (p < 0.01). These findings demonstrate that luminance levels of stimuli can affect colour discrimination and what dogs are able to see on computer screens. These results have important implications in how cognition is studied in dogs through the use of presenting stimuli on monitors.

Group and kin recognition via olfactory cues in chimpanzees (Pan troglodytes).

Primates were traditionally thought to have a reduced sense of smell. Although there is now evidence that olfaction plays a greater role in primate social life than previously assumed, research on the sense of smell in non-human apes is scarce. Chimpanzees sniff the ground and vegetation on boundary patrols, but the function of this behaviour is unclear. Since chimpanzees are highly territorial and can kill individuals that do not belong to their own community, sniffing might function to gather information about conspecifics, particularly concerning group membership and kinship. To investigate whether chimpanzees recognize group members and kin via olfactory cues, we conducted behavioural bioassays on two groups of chimpanzees at Leipzig Zoo. In a pilot study, we found that chimpanzees responded more strongly to urine than to faeces or body odour. We then presented urine from group members, outgroup individuals and an unscented control in aerated boxes using a simultaneous discrimination task. The first behaviour after a chimpanzee first approached a box was related to olfaction (sniffing, nose within 20 cm, licking) in 83% of cases, highlighting the importance of olfaction as a general investigation mechanism in this species. Chimpanzees sniffed significantly longer at urine stimuli than the control and significantly longer at odours from outgroup individuals than those from group members. Furthermore, the duration of sniffing was positively correlated with relatedness. Our results suggest that chimpanzees use olfactory cues to obtain information about social relationships and fill a gap in our understanding of primate chemical communication.

Seeing morphing faces of own- and other-race: the development of face discrimination in 3- to 7-year-old Taiwanese children

Introduction. Previous studies on the other-race effect (ORE) in preschoolers and children mostly focused on recognition memory performance; however, the onset of ORE has been inconclusive across studies. Here we wish to explore the development of the ORE in 3- to 7-year-old Taiwanese children with a simultaneous morphing face discrimination task. Method. A set of morphed images of Caucasian and Asian male and female faces were used. In Experiment 1, 3- to 4-year-old children (N = 41) were tested with a forced-choice simultaneous pointing task. They viewed an Asian or Caucasian target parent face followed by a pair of comparison faces, with one being the "same parent" face and the other as a "different" morphed face (i.e., 30%, 60%, or 90% contribution from the other parent face). Children were asked to point out the same face with their fingers. In Experiment 2, 5- to 7-year-old children (N = 45) and adults (N=16) were tested with a forced-choice simultaneous matching task. The stimuli were the same as in Exp. 1, but the participants were asked to identify the face that was different from the target with keypress. Results. The results showed that, for all age groups, the accuracies of correctly pointing to the same or identifying the different face increased as the morph level increased, and the mean accuracies for the Asian- and Caucasian-parent conditions were about equal. Adults and 5- to 7-year-old children outperformed 3- and 4-year-old children at all morph levels; the performance of 7 year-olds at the three morph levels started to look adult-like. Conclusion. In sum, using the simultaneous morphing face pointing/matching task, the present study did not reveal an ORE in Taiwanese children aged between 3 and 7. However, a clear developmental progression in processing morphing faces was evident between young children and adults. Meeting abstract presented at VSS 2018

The effect of stimulus duration on over-selectivity: Evidence for the role of within-compound associations.

The phenomenon whereby behavior becomes controlled by one aspect of the environment at the expense of other aspects of the environment (stimulus overselectivity) is widespread across many intellectual and developmental disabilities. However, the theoretical mechanisms underpinning overselectivity are not understood. Given similarities between overselectivity and overshadowing, exploring overselectivity using associative learning paradigms might allow better theoretical understanding of the phenomenon. Three experiments explored overselectivity using a simultaneous discrimination task with typically developing participants undergoing a cognitively demanding task. Experiment 1 investigated whether stimulus duration effects found within the overshadowing literature also occurred in an overselectivity paradigm, and demonstrated that greater overselectivity was observed when stimuli were presented for short durations (2s and 5s) compared with longer durations (10s). Experiment 2 demonstrated that a posttraining revaluation procedure resulted in retrospective revaluation for stimuli presented at shorter durations (2s) and mediated extinction for stimuli presented at longer durations (10s). Such results replicate findings from the overshadowing literature that have been interpreted in terms of within-compound associations while also supporting assumptions made by an extended comparator hypothesis. Experiment 3 uses an additional control condition to further demonstrate that the retrospective revaluation is a genuine revaluation effect. Additionally, the experiment provides further evidence for the within-compound association explanation of the results through manipulating the consistency with which elements of a compound were paired during training. Taken together, the findings highlight the necessity to consider the role of within-compound associations in overselectivity, allowing for a better understanding of overselectivity effects. (PsycINFO Database Record

Valence of Facial Cues Influences Sheep Learning in a Visual Discrimination Task.

Sheep are one of the most studied farm species in terms of their ability to process information from faces, but little is known about their face-based emotion recognition abilities. We investigated (a) whether sheep could use images of sheep faces taken in situation of varying valence as cues in a simultaneous discrimination task and (b) whether the valence of the situation affects their learning performance. To accomplish this, we photographed faces of sheep in three situations inducing emotional states of neutral (ruminating in the home pen) or negative valence (social isolation or aggressive interaction). Sheep (n = 35) first had to learn a discrimination task with colored cards. Animals that reached the learning criterion (n = 16) were then presented with pairs of images of the face of a single individual taken in the neutral situation and in one of the negative situations. Finally, sheep had to generalize what they had learned to new pairs of images of faces taken in the same situation, but of a different conspecific. All sheep that learned the discrimination task with colored cards reached the learning criterion with images of faces. Sheep that had to associate a negative image with a food reward learned faster than sheep that had to associate a neutral image with a reward. With the exception of sheep from the aggression-rewarded group, sheep generalized this discrimination to images of faces of different individuals. Our results suggest that sheep can perceive the emotional valence displayed on faces of conspecifics and that this valence affects learning processes.

Using the Implicit Association Test and Choice to Measure the Within-Trial Contrast Effect in Human Adults

When humans and nonhuman animals work hard to achieve a goal, they generally appreciate the results more than when the goal requires little effort to be achieved. The within-trial contrast (WTC) hypothesis explains this phenomenon in terms of the contrast between individuals’ relative hedonic states. We examined the validity of the WTC hypothesis by incorporating an implicit association test (IAT) as a measure of implicit preference in procedures similar to those of Tsukamoto, Kohara, and Takeuchi (Learning & Behavior, 45, 135–146, 2017), who reported emergence of the WTC effect in humans. As a procedural consideration, we also changed the following event to the presentation of a single stimulus instead of a simultaneous discrimination task. We manipulated the effort involved and difficulty of a preceding task by varying the interresponse time (IRT) in differential reinforcement with a low response rate schedule that involved a limited hold. Influences of training were tested in two measures: the choice test and the IAT. Results revealed that in the choice test participants showed significant preference for stimuli that followed the effortful task, which involved a longer IRT even though the effect size was smaller than in the previous study. However, in the IAT, we could not observe the association that the WTC hypothesis presumed. Inconsistency between the choice test and the IAT suggests that preference arising from the WTC paradigm might be caused by a factor other than a change in hedonic state, leaving the question of whether we succeeded in selecting an appropriate measure.

Does hearing loss affect the use of information at different frequencies? Results from a simultaneous tonal pattern discrimination task in normal-hearing and hearing-impaired listeners

This study extends previous work [Roverud et al., Trends Hear, 20, 1-17, 2016] reporting differences between normal-hearing (NH) and hearing-impaired (HI) listeners in their use of low- vs. high-frequency information. In that study, listeners identified well-learned tonal patterns presented simultaneously at two center frequencies (CFs). The CFs corresponded to lesser and greater hearing loss in the HI group. Despite matched identification performance at each CF in quiet, when patterns were presented simultaneously, HI listeners were better able to identify patterns at the CF corresponding to better hearing. Here, we extend that work using a discrimination rather than identification task, with less reliance on recall. Each trial consisted of three intervals, each containing simultaneous tonal patterns at two CFs. Individual frequency discrimination thresholds were used to set the separation between elements within each pattern, ensuring equal discriminability across listeners and CFs. The first (referent) interval contains two simultaneous random-frequency patterns, one at each CF. One of the two sequential comparison intervals contains a match to the referent pattern at one of the CFs, and the listener indicates the comparison interval containing the match. Results examining differences for the two CFs across NH and HI listeners will be presented. [Work supported by NIH/NIDCD.]

Reconsideration of Serial Visual Reversal Learning in Octopus (Octopus vulgaris) from a Methodological Perspective.

Octopuses (Octopus vulgaris) are generally considered to possess extraordinary cognitive abilities including the ability to successfully perform in a serial reversal learning task. During reversal learning, an animal is presented with a discrimination problem and after reaching a learning criterion, the signs of the stimuli are reversed: the former positive becomes the negative stimulus and vice versa. If an animal improves its performance over reversals, it is ascribed advanced cognitive abilities. Reversal learning has been tested in octopus in a number of studies. However, the experimental procedures adopted in these studies involved pre-training on the new positive stimulus after a reversal, strong negative reinforcement or might have enabled secondary cueing by the experimenter. These procedures could have all affected the outcome of reversal learning. Thus, in this study, serial visual reversal learning was revisited in octopus. We trained four common octopuses (O. vulgaris) to discriminate between 2-dimensional stimuli presented on a monitor in a simultaneous visual discrimination task and reversed the signs of the stimuli each time the animals reached the learning criterion of ≥80% in two consecutive sessions. The animals were trained using operant conditioning techniques including a secondary reinforcer, a rod that was pushed up and down the feeding tube, which signaled the correctness of a response and preceded the subsequent primary reinforcement of food. The experimental protocol did not involve negative reinforcement. One animal completed four reversals and showed progressive improvement, i.e., it decreased its errors to criterion the more reversals it experienced. This animal developed a generalized response strategy. In contrast, another animal completed only one reversal, whereas two animals did not learn to reverse during the first reversal. In conclusion, some octopus individuals can learn to reverse in a visual task demonstrating behavioral flexibility even with a refined methodology.

Over-Selectivity is Related to Autism Quotient and Empathizing, But not to Systematizing

The relationships of autism quotient (AQ), systematizing (SQ), and empathizing (EQ), with over-selectivity were explored to assess whether over-selectivity is implicated in complex social skills, which has been assumed, but not experimentally examined. Eighty participants (aged 18–60) were trained on a simultaneous discrimination task (AB+CD−), and tested in extinction on the degree to which they had learned about both elements of the reinforced (AB) compound. Higher AQ and lower EQ scorers demonstrated greater over-selectivity, but there was no relationship between SQ and over-selectivity. These results imply that high AQ scorers perform similarly to individuals with ASD on this cognitive task, and that over-selectivity may be related to some complex social skills, like empathy.

Same/Different Abstract Concept Learning by Archerfish (Toxotes chatareus).

While several phylogenetically diverse species have proved capable of learning abstract concepts, previous attempts to teach fish have been unsuccessful. In this report, the ability of archerfish (Toxotes chatareus) to learn the concepts of sameness and difference using a simultaneous two-item discrimination task was tested. Six archerfish were trained to either select a pair of same or different stimuli which were presented simultaneously. Training consisted of a 2-phase approach. Training phase 1: the symbols in the same and different pair did not change, thereby allowing the fish to solve the test through direct association. The fish were trained consecutively with four different sets of stimuli to familiarize them with the general procedure before moving on to the next training phase. Training phase 2: six different symbols were used to form the same or different pairs. After acquisition, same/different concept learning was tested by presenting fish with six novel stimuli (transfer test). Five fish successfully completed the first training phase. Only one individual passed the second training phase, however, transfer performance was consistent with chance. This individual was given further training using 60 training exemplars but the individual was unable to reach the training criterion. We hypothesize that archerfish are able to solve a limited version of the same/different test by learning the response to each possible stimulus configuration or by developing a series of relatively simple choice contingencies. We conclude that the simultaneous two-item discrimination task we describe cannot be successfully used to test the concepts of same and different in archerfish. In addition, despite considerable effort training archerfish using several tests and training methods, there is still no evidence that fish can learn an abstract concept-based test.

Analyzing the Stimulus Control Acquisition in Simple Discrimination Tasks through Eye Movement

In order to investigate whether simultaneous or successive presentation of stimuli is related to the duration of eye fixation (i.e., the time spent gazing a specific stimulus), this study described the eye movements of young adults in simultaneous and successive simple discrimination tasks. Using 12 landscape scenes as visual stimuli, three participants were exposed to a simple discrimination training with simultaneously presented stimuli (Si Procedure) and then to a second simple discrimination training with successively presented stimuli (Su Procedure). Another three participants were exposed to the Procedure in the opposite order. In both cases, the learning criterion was that at least 90% of the responses should be correct in one block. Eye movements were recorded during the whole experiment. Participants achieved the learning criteria in both procedures. Beyond that, eye fixation time in the Su Procedure was higher than in the Si Procedure, regardless of the training sequence. Taken together with previous results in different experiments, our findings suggest that the duration of eye fixation plays a central role in the establishment of different stimulus control topographies.

Hippocampus, perirhinal cortex, and complex visual discriminations in rats and humans.

Structures in the medial temporal lobe, including the hippocampus and perirhinal cortex, are known to be essential for the formation of long-term memory. Recent animal and human studies have investigated whether perirhinal cortex might also be important for visual perception. In our study, using a simultaneous oddity discrimination task, rats with perirhinal lesions were impaired and did not exhibit the normal preference for exploring the odd object. Notably, rats with hippocampal lesions exhibited the same impairment. Thus, the deficit is unlikely to illuminate functions attributed specifically to perirhinal cortex. Both lesion groups were able to acquire visual discriminations involving the same objects used in the oddity task. Patients with hippocampal damage or larger medial temporal lobe lesions were intact in a similar oddity task that allowed participants to explore objects quickly using eye movements. We suggest that humans were able to rely on an intact working memory capacity to perform this task, whereas rats (who moved slowly among the objects) needed to rely on long-term memory.

Responding by exclusion in Wistar rats in a simultaneous visual discrimination task.

Responding by exclusion is to select a correct alternative by rejecting other potential alternatives. Studies describe this ability in some mammals and birds. However, this type of performance has not been reported in rodents. The aim of this study was to verify the occurrence of responding by exclusion in Wistar rats after a baseline of simple simultaneous visual discrimination. Six male Wistar learned nose-poking tunnels displaying visual stimuli (projected geometric shapes) in an operant chamber. After establishing the simultaneous discrimination baseline, three probe sessions were conducted. In each session, there was a novelty-control probe (a new stimulus was presented together with a stimulus trained as the S(+)) and an exclusion probe (a second new stimulus was presented simultaneously with a stimulus trained as the S(-)). Only one rat responded to the new stimulus in one of the three novelty probe trials. Four rats responded to the three new stimuli and one responded to the new stimulus in two of the three exclusion probes. One subject responded to the S(-) in all the exclusion probes. Five of the six subjects were therefore able to choose the new stimulus, rejecting stimuli trained as the S(-). This is the first experimental evidence for performance by exclusion in rats.

Discrimination and Reversal Learning by Toddlers Aged 15-23 Months.

Few studies have investigated simple discrimination and discrimination reversal learning by children younger than 2 years. Extant research has shown that teaching discrimination reversals may be challenging with this population. We used social reinforcement and correction procedures to teach simple simultaneous discrimination and discrimination reversal tasks involving three pairs of animal pictures displayed in a paper notebook. Participants were eight typically-developing toddlers aged 15-23 months. All learned at least one simple discrimination/discrimination reversal problem. Four children learned all problems and showed evidence of learning set formation. Perhaps surprisingly, discrimination reversals were sometimes learned more rapidly than original discriminations. The procedures suggest a potentially efficient methodology for investigating more complex aspects of relational learning in toddlers.

Exclusion performance in visual simple discrimination in dogs (Canis familiaris).

based on exclusion have been investigated in different species because of its emergent nature, leading to evidence of rudimentary symbolic behavior in non-verbal organisms. Simple discrimination procedures provide a simple method to investigate exclusion performance, in which each trial consists of the simultaneous presentation of two stimuli, one with a positive function (S+) and one with a negative function (S-). In exclusion probe trials, an undefined stimulus (UnS) is presented with a familiar S - , and choices based on exclusion may lead to choosing the UnS, excluding the previously known S - . Novelty control trials (S + /UnS) are also conducted to assess the possible preference for the UnS. In this case, if performance is not controlled by novelty, then the subjects must choose the S + and not the UnS. The present study investigated exclusion performance in visual simple simultaneous discrimination tasks in eight dogs. The results indicated that seven of eight dogs showed evidence of exclusion performance (p < .05). These findings corroborate the literature that shows that dogs are capable of responding by exclusion, suggesting that potentially symbolic behavior may rely on basic behavioral learning and conditioning principles.