Pictorial similarity judgments and the organization of visual memory in the rhesus monkey

The organization of visual memory for pictures was studied in the rhesus monkey. Two monkeys were tested in a same/different task in which sequentially presented pictures were compared to each other in a pair-wise fashion. The resulting confusion matrixes were analyzed using a multidimensional scaling procedure to obtain two- and three-dimensional graphic representations of the stimulus space. In Experiment 1, the monkeys' confusion errors caused pictures of human and rhesus monkey faces to fall in the same region of multidimensional space, which suggested that the monkeys categorized facial stimuli. A similar effect was found for pictures of different types of fruit. Experiment 2 replicated the categorization of faces with a more diverse collection of human and nonhuman primate faces. Experiment 3 explored the fruit category by varying stimulus attributes orthogonally. The results from this experiment showed that both monkeys encoded the pictures in this category by type of fruit (apples or grapes) and color (red or yellow). Taken together, these studies indicate that rhesus monkeys will treat some classes of pictorial stimuli categorically in visual memory.     

Abstract-concept learning and list-memory processing by capuchin and rhesus monkeys

Three capuchin monkeys (Cebus apella) touched the lower of 2 pictures (same) or a white rectangle (different), increased same/different abstract-concept learning (52% to 87%) with set-size increases (8 to 128 pictures), and were better than 3 rhesus monkeys (Macaca mulatta). Three other rhesus that touched the top picture before choices learned similar to capuchins but were better at list-memory learning. Both species' serial position functions were similar in shape and changes with retention delays. Other species showed qualitatively similar shape changes but quantitatively different time-course changes. In abstract-concept learning, qualitative similarity was shown by complete concept learning, whereas a quantitative difference would have been a set-size slope difference. Qualitative similarity is discussed in relation to general-process versus modular cognitive accounts.     

Mechanisms of same/different abstract-concept learning by rhesus monkeys (Macaca mulatta)

Experiments with 9 rhesus monkeys (Macaca mulatta) showed, for the first time, that abstract-concept learning varied with the training stimulus set size. In a same/different task, monkeys required to touch a top picture before choosing a bottom picture (same) or white rectangle (different) learned rapidly. Monkeys not required to touch the top picture or presented with the top picture for a fixed time learned slowly or not at all. No abstract-concept learning occurred after 8-item training but progressively improved with larger set sizes and was complete following 128-item training. A control monkey with a constant 8-item set ruled out repeated training and testing. Contrary to the unique-species account, it is argued that different species have quantitative, not qualitative, differences in abstract-concept learning.     

SPELLING AND EMERGENT PICTURE-PRINTED WORD RELATIONS ESTABLISHED WITH DELAYED IDENTITY MATCHING TO COMPLEX SAMPLES

Students with academic deficits learned delayed matching-to-sample tasks that used complex sample stimuli, each consisting of a picture and a printed word. A touch to the sample complex removed it from the computer display and produced either picture comparisons or a choice pool of letters. If the comparisons were pictures, selecting the picture identical to the preceding sample was reinforced. If the letters appeared, letter-by-letter construction of the preceding printed word sample was reinforced. The procedure engendered new constructed-response spelling performances and arbitrary relations among pictures and printed words in matching to sample. The emergence of relations among different sets of printed words (paired with the same pictures) suggested classes of equivalent stimuli. Outcome tests involving spoken words as sample stimuli suggested expansion of subjects' spelling repertoires and stimulus classes.     

Same/different abstract-concept learning by pigeons

Eight pigeons were trained and tested in a simultaneous same/different task. After pecking an upper picture, they pecked a lower picture to indicate same or a white rectangle to indicate different. Increases in the training set size from 8 to 1,024 items produced improved transfer from 51.3% to 84.6%. This is the first evidence that pigeons can perform a two-item same/different task as accurately with novel items as training items and both above 80% correct. Fixed-set control groups ruled out training time or transfer testing as producing the high level of abstract-concept learning. Comparisons with similar experiments with rhesus and capuchin monkeys showed that the ability to learn the same/different abstract concept was similar but that pigeons require more training exemplars.     

Concept of uprightness in baboons: assessment with pictures of realistic scenes

How nonhuman primates process pictures of natural scenes or objects remains a matter of debates. This issue was addressed in the current research by questioning the processing of the canonical orientation of pictures in baboons. Two adult guinea baboons were trained to use an interactive key (IK) on a touch-screen to change the orientation of target pictures showing humans or quadruped mammals until upright. In experiment 1, both baboons successfully learned to use the IK when that key induced a 90 degrees rightward rotation of the picture, but post-training transfer of performance did not occur to novel pictures of natural scenes due to potential motor biases. In Experiment 2, a touch on IK randomly displayed the pictures in any of the four cardinal orientations. Baboons successfully learned the task, but transfer to novel pictures could only be demonstrated after they had been exposed to 360-480 pictures in that condition. Experiment 3 confirmed positive transfers to novel pictures, and showed that both the figure and background information controlled the behavior. Our research on baboons therefore demonstrates the development and use of an "upright" concept, and indicates that picture processing modes strongly depend on the subject's past experience with naturalistic pictorial stimuli.     

Concept learning set‐size functions for Clark's nutcrackers

Same/Different abstract‐concept learning by Clark's nutcrackers (Nucifraga columbiana) was tested with novel stimuli following learning of training set expansion (8, 16, 32, 64, 128, 256, 512, and 1024 picture items). The resulting set‐size function was compared to those from rhesus monkeys (Macaca mulatta), capuchin monkeys (Cebus apella), and pigeons (Columba livia). Nutcrackers showed partial concept learning following initial eight‐item set learning, unlike the other species (Magnotti, Katz, Wright, & Kelly, 2015). The mean function for the nutcrackers' novel‐stimulus transfer increased linearly as a function of the logarithm of training set size, which intersected its baseline function at the 128‐item set size. Thus, nutcrackers on average achieved full concept learning (i.e., transfer statistically equivalent to baseline performance) somewhere between set sizes of 64 to 128 items, similar to full concept learning by monkeys. Pigeons required a somewhat larger training set (256 items) for full concept learning, but results from other experiments (initial training and transfer with 32‐ and 64‐item set sizes) suggested carryover effects with smaller set sizes may have artificially prolonged the pigeon's full concept learning. We find it remarkable that these diverse species with very different neural architectures can fully learn this same/different abstract concept, and (at least under some conditions) do so with roughly similar sets sizes (64‐128 items) and numbers of training exemplars, despite initial concept learning advantages (nutcrackers), learning disadvantages (pigeons), or increasing baselines (monkeys).     

Monkeys' recognition memory for complex pictures and the effect of fornix transection

Two monkeys were trained in a running-recognition task with complex pictures. The task was made gradually more difficult by increasing the number of intervening items between the first and second presentation of the same picture. Before undergoing an operation in which the fornix was transected, both monkeys performed above 90% correct even in the most difficult task set, with up to 18 intervening items. After operation neither monkey could reliably perform a much easier task with only 2.7 intervening items on average. This impairment is comparable to that of human amnesic patients in similar tasks.     

A case for restricted-domain relational learning

Monkeys and pigeons learned a same/different task with pairs that were selected from a training set of eight picture stimuli. They showed no novel-stimulus transfer and hence no abstract-concept learning. They were also tested with novel pairs of the eight training pictures (i.e., combinations that had not been used in training) and with inverted pictures of the training pairs. If the subjects had learned the task item-specifically (e.g., if—then or configural learning), they should have failed these tests, but they performed well with novel combinations of training pictures and inverted pictures, suggesting that they learned the task relationally (i.e., on the basis of the relationship between the two pictures that were presented in each trial). This somewhat paradoxical conclusion of relational learning in the absence of abstract-concept learning is contrary to most theories of abstract-concept learning. The implications of this conclusion are discussed in the context of restricted-domain relational learning.     

Sex categorization of conspecific pictures in Japanese monkeys (Macaca fuscata)

We investigated whether monkeys discriminate the sex of individuals from their pictures. Whole-body pictures of adult and nonadult monkeys were used as stimuli. Two male Japanese monkeys were trained for a two-choice sex categorization task in which each of two choice pictures were assigned to male and female, respectively. Following the training, the monkeys were presented with novel monkey pictures, and whether they had acquired the categorization task was tested. The results suggested that while monkeys discriminate between the pictures of adult males and females, discrimination of nonadult pictures was difficult. Partial presentations of the pictures showed that conspicuous and sexually characteristic parts (i.e., underbellies including male scrotums or breasts including female nipples) played an important role in the sex categorization.     

On the limits of the matching concept in monkeys (Cebus apella).

Two cebus monkeys, with many years of experience matching a variety of static visual stimuli (forms and colors) within a standard matching-to-sample paradigm, were trained to press a left lever when a pair of displayed static stimuli were the same and to press a right lever when they were different. After learning the same/different task, the monkeys were tested for transfer to dynamic visual stimuli (flashing versus steady green disks), with which they had no previous experience. Both failed to transfer to the dynamic stimuli. A third monkey, also with massive past experience matching static visual stimuli, was tested for transfer to the dynamic stimuli within our standard matching paradigm, and it, too, failed. All 3 subjects were unable to reach a moderate acquisition criterion despite as many as 52 sessions of training with the dynamic stimuli. These results provide further evidence that, in monkeys, the matching (or identity) concept has a very limited reach; they consequently do not support the view held by some theorists that an abstract matching concept based on physical similarity is a general endowment of animals.     

Conditions of directed attention inhibit recognition performance for explicitly presented target-aligned irrelevant stimuli

The fate of irrelevant and overtly presented stimuli that was temporally aligned with an attended target in a separate task was explored. Seitz and Watanabe (2003) demonstrated that if an irrelevant motion stimulus was implicit (i.e., subthreshold), a later facilitation for the same motion direction was observed if the previously presented implicit motion (of the same direction) was temporally aligned with the presence of an attended target. Later research, however, demonstrated that if the motion stimulus aligned with the attended target was explicit (i.e., suprathreshold), a later inhibition was observed (Tsushima, Seitz, & Watanabe, 2008). The current study expands on this by using more salient stimuli (words and pictures) in an inattentional blindness paradigm, and suggests that when attention is depleted, recognition for target-aligned task-irrelevant items is impaired in a subsequent recognition task. Participants were required to respond to either immediate picture, or word, repetitions in a stream of simultaneously presented line drawings and written words, and later given a surprise recognition test that measured recognition for the words or the pictures. When analyzing word recognition performance after attention had been directed to the pictures, words that had appeared simultaneously with a picture repetition in the repetition detection task were recognized at levels significantly below chance. The same inhibition was mirrored when testing for picture recognition after having attended to the words in the repetition detection task. These data suggest an inhibitory mechanism that is exhibited in later recognition tests for salient information that was previously unattended and had been simultaneously being presented with an attended target in a different task.     

Does the generation effect occur for pictures?

The generation effect is the finding that self-generated stimuli are recalled and recognized better than read stimuli. The effect has been demonstrated primarily with words. This article examines the effect for pictures in two experiments: Subjects named complete pictures (name condition) and fragmented pictures (generation condition). In Experiment 1, memory was tested in 3 explicit tasks: free recall, yes/no recognition, and a source-monitoring task on whether each picture was complete or fragmented (the complete/incomplete task). The generation effect was found for all 3 tasks. However, in the recognition and source-monitoring tasks, the generation effect was observed only in the generation condition. We hypothesized that absence of the effect in the name condition was due to the sensory or process match effect between study and test pictures and the superior identification of pictures in the name condition. Therefore, stimuli were changed from pictures to their names in Experiment 2. Memory was tested in the recognition task, complete/incomplete task, and second source-monitoring task (success/failure) on whether each picture had been identified successfully. The generation effect was observed for all 3 tasks. These results suggest that memory of structural and semantic characteristics and of success in identification of generated pictures may contribute to the generation effect.     

Crossmodal semantic priming by naturalistic sounds and spoken words enhances visual sensitivity

We propose a multisensory framework based on Glaser and Glaser's (1989) general reading-naming interference model to account for the semantic priming effect by naturalistic sounds and spoken words on visual picture sensitivity. Four experiments were designed to investigate two key issues: First, can auditory stimuli enhance visual sensitivity when the sound leads the picture as well as when they are presented simultaneously? And, second, do naturalistic sounds (e.g., a dog's "woofing") and spoken words (e.g., /d?g/) elicit similar semantic priming effects? Here, we estimated participants' sensitivity and response criterion using signal detection theory in a picture detection task. The results demonstrate that naturalistic sounds enhanced visual sensitivity when the onset of the sounds led that of the picture by 346 ms (but not when the sounds led the pictures by 173 ms, nor when they were presented simultaneously, Experiments 1-3A). At the same SOA, however, spoken words did not induce semantic priming effects on visual detection sensitivity (Experiments 3B and 4A). When using a dual picture detection/identification task, both kinds of auditory stimulus induced a similar semantic priming effect (Experiment 4B). Therefore, we suggest that there needs to be sufficient processing time for the auditory stimulus to access its associated meaning to modulate visual perception. Besides, the interactions between pictures and the two types of sounds depend not only on their processing route to access semantic representations, but also on the response to be made to fulfill the requirements of the task.     

The effects of emotional stimuli on target detection: indirect and direct resource costs

The present study was designed to explore the performance costs of negative emotional stimuli in a vigilance task. Forty participants (20 women) performed a vigilance task in two conditions: one with task-irrelevant negative-arousing pictures and one with task-irrelevant neutral pictures. In addition to performance, we measured subjective state (energetic arousal, tense arousal, task-related and task-unrelated thoughts) and frontal cerebral activity with near infrared spectroscopy. Overall performance in the negative picture condition was lower than in the neutral picture condition and the negative picture condition had elevated levels of energetic arousal, tense arousal and task-related thoughts. Moreover, there was a significant relationship between the impact of the negative pictures on tense arousal and task-related thoughts and the impact of the negative pictures on performance (in comparison to the neutral picture stimuli task). These results provide support for indirect cost models of negative emotional stimuli on target detection performance.     

Picture recognition of food by macaques (<Emphasis Type="Italic">Macaca silenus</Emphasis>)

Pictorial representations of three-dimensional objects are often used to investigate animal cognitive abilities; however, investigators rarely evaluate whether the animals conceptualize the two-dimensional image as the object it is intended to represent. We tested for picture recognition in lion-tailed macaques by presenting five monkeys with digitized images of familiar foods on a touch screen. Monkeys viewed images of two different foods and learned that they would receive a piece of the one they touched first. After demonstrating that they would reliably select images of their preferred foods on one set of foods, animals were transferred to images of a second set of familiar foods. We assumed that if the monkeys recognized the images, they would spontaneously select images of their preferred foods on the second set of foods. Three monkeys selected images of their preferred foods significantly more often than chance on their first transfer session. In an additional test of the monkeys’ picture recognition abilities, animals were presented with pairs of food images containing a medium-preference food paired with either a high-preference food or a low-preference food. The same three monkeys selected the medium-preference foods significantly more often when they were paired with low-preference foods and significantly less often when those same foods were paired with high-preference foods. Our novel design provided convincing evidence that macaques recognized the content of two-dimensional images on a touch screen. Results also suggested that the animals understood the connection between the two-dimensional images and the three-dimensional objects they represented.     

Age-related changes in event-cued visual and auditory prospective memory proper

We rely upon prospective memory proper (ProMP) to bring back to awareness previously formed plans and intentions at the right place and time, and to enable us to act upon those plans and intentions. To examine age-related changes in ProMP, younger and older participants made decisions about simple stimuli (ongoing task) and at the same time were required to respond to a ProM cue, either a picture (visually cued ProM test) or a sound (auditorily cued ProM test), embedded in a simultaneously presented series of similar stimuli (either pictures or sounds). The cue display size or loudness increased across trials until a response was made. The cue size and cue loudness at the time of response indexed ProMP. The main results showed that both visual and auditory ProMP declined with age, and that such declines were mediated by age declines in sensory functions (visual acuity and hearing level), processing resources, working memory, intelligence, and ongoing task resource allocation.     

Formation of the sameness-difference concept by Japanese monkeys from a small number of color stimuli

Japanese monkeys were trained to form the sameness-difference concept. In Experiment 1, four monkeys were trained with two colors to discriminate matching stimulus pairs from nonmatching pairs by reinforcing only lever-pressing responses to matching pairs with a variable-interval schedule. Three monkeys showed successful transfer of this discrimination to two new colors, thus demonstrating that some Japanese monkeys are able to form this relational concept from a minimum number of stimuli. In Experiment 2, two monkeys were trained, in a Yes/No procedure with three colors, to press one lever under matching pairs and another lever under nonmatching pairs. Poor transfer performances to three new colors suggest that simultaneously establishing two different response patterns to matching and nonmatching pairs is ineffective in forming the concept. In Experiment 3, the amount of transfer to three new colors after mastering a standard three-color matching-to-sample task was compared with that of a modified task in which correct responses were reinforced with a within-trial variable-interval schedule. All three monkeys showed greater transfer with the modified procedure. The results suggest that the variable-interval schedule adopted within trials is effective in forming the sameness-difference concept.     

Semantic negative priming in picture categorization and naming

Ignoring a particular stimulus can hamper subsequent attended processing of the same stimulus, a phenomenon known as 'negative priming'. Previous research has yielded partial support for the claim that the effect results from the attentional inhibition of central representations, as suggested by the fact that it appears to extend to semantic associates of ignored stimuli. In the current experiment, participants categorized or named pictorial stimuli with superimposed distractor pictures; the effect of unrelated, identical, or categorically related previously ignored pictures was investigated. Furthermore, visual similarity between categorically related picture pairs was manipulated in the naming task. The results indicated negative priming from identical ignored pictures irrespective of task. However, semantic negative priming was observed in the categorization task only. In the naming task, even visual overlap between categorically related picture pairs failed to induce negative priming. These findings argue against a central locus of the negative priming effect.     

Time of day affects implicit memory for unattended stimuli

We investigated whether circadian arousal affects perceptual priming as a function of whether stimuli were attended or ignored during learning. We tested 160 participants on- and off-peak with regards to their circadian arousal. In the study phase, they were presented with two superimposed pictures in different colours. They had to name the pictures of one colour while ignoring the others. In the test phase, they were presented with the same and randomly intermixed new pictures. Each picture was presented in black colour in a fragment completion task. Priming was measured as the difference in fragmentation level at which the pictures from the study phase were named compared to the new pictures. Priming was stronger for attended than ignored pictures. Time of day affected priming only for ignored pictures, with stronger priming effects off-peak than on-peak. Thus, circadian arousal seems to favour the encoding of unattended materials specifically at off-peak.