Autoshaping in the rat: The effects of localizable visual and auditory signals for food

Two experiments investigated autoshaping in rats to localizable visual and auditory conditioned stimuli predicting response-independent food. In Experiment 1 considerable conditioned-stimulus approach behavior was generated by a localizable visual conditioned stimulus that was situated approximately 35 cm from the food tray. Using the same apparatus in Experiment 2 we found that the conditioned-stimulus approach was generated only to a visual conditioned stimulus and not to a localizable auditory conditioned stimulus even though subjects (1) could discriminate presentations of the auditory conditioned stimulus, (2) had associated it with food, (3) could localize it, and (4) would approach the auditory stimulus if this behavior constituted an instrumental response to food. The predominant conditioned responses to the auditory stimuli were goal tracking (entering the food tray) and orienting towards the food-paired conditioned stimulus by head turning and rearing and turning. These results imply that rats do not invariably approach a localizable appetitive Pavlovian conditioned stimulus but that stimulus-approach responses depend on the nature and modality of the conditioned stimulus.     

Operant conditioning in the newly hatched chicken

Techniques are described for conditioning key-pecking reinforced with food and for recording cheeping in newly hatched chickens. A mirror in the test box is essential when conditioning isolated chickens up to five or more days old. Conditioning proceeds more rapidly when frequently pecked objects and materials that move when scratched are not present. Stimulus control over key-pecking is present in the three-day-old chicken and multiple fixed-ratio, fixed-interval schedule control develops in succeeding days. In young chickens, pecking and cheeping are inversely related. The newly hatched chicken is useful for pharmacological studies and appears to offer other advantages for behavioral studies.     

Infant shifting attention from an adult’s face to an adult’s hand: a precursor of joint attention

Two experiments were designed to investigate shifting attention from an adult’s face to an adult’s hand by 3- and 4-month-olds. In Experiment 1, 24 infants were presented with five types of hand gestures by their mothers and a stranger. Experiment 2 was given to 22 infants with the same procedures, except for the addition of a head inclining while pointing to objects. The results were: (1) after encountering an averted head repeatedly, the infants shifted their attention from the adult’s face to the moving hand and objects; they oriented to what the adult was attending to. (2) The moving head improved the rate of infants turning their heads to the same direction as the adult. The conclusion was averted head and eyes play a major role in infants’ orienting to an adult’s hand. A hand was a shared visual target during the adult’s object performance, indicating that infants’ orientation to the adults’ hand is a precursor stage of joint visual attention.     

Action priming by briefly presented objects

Three experiments investigated how visual objects prime the actions they afford. The principal concern was whether such visuomotor priming depends upon a concurrent visual input--as would be expected if it is mediated by on-line dorsal system processes. Experiment 1 showed there to be essentially identical advantages for making afforded over non-afforded responses when these were made to objects still in view and following brief (30 or 50 ms) object exposures that were backward masked. Experiment 2 showed that affordance effects were also unaffected by stimulus degradation. Finally, Experiment 3 showed there to be statistically equal effects from images of objects and their names. The results suggest that an active object representation is sufficient to generate affordance compatibility effects based on associated actions, whether or not the object is concurrently visible.     

Effects of imprinting and isolation on aggressive responses in chicks

The importance of isolation and imprinting as separate factors influencing early aggressive responses in chicks (Gallus gallus) was studied in two separate experiments. In addition the effect of the presence or absence of the imprinting stimulus in the test situation was examined in Experiment 1. Neither imprinting per se, nor the presence of the imprinting stimulus significantly affected aggressiveness. Rearing conditions (isolation vs social rearing) did, however, influence aggressive responses. Isolated chicks were significantly more aggressive than socially reared buds. The adaptedness of selective aggression in socially (naturally) reared chicks, as well as the indiscriminant aggressiveness caused by social deprivation is discussed.     

The shapes associated with approach/avoidance words

People prefer curved and symmetrical shapes to their angular and asymmetrical counterparts. While it is known that stimulus valence is central to approach and avoidance motivation, the exact nature of the relationship between curvature/symmetry and approach/avoidance motivation still needs to be clarified. Experiment 1 was designed to investigate whether simple shapes are associated with approach and avoidance words. Participants found it easier to match more symmetrical shapes with approach words. In Experiment 2, symmetry was differentially associated with approach words and was rated significantly higher on the approach dimension than asymmetry. Next, we assessed whether object valence and object curvature (Experiment 3) or symmetry (Experiment 4) would lead to different associations to approach and avoidance words. Only object valence had a significant influence on participants’ ratings, with the positively-valenced objects being more closely associated with approach words than their negatively-valenced counterparts. These results highlight the complex relation between visual properties of objects, their valence, and appetitive and aversive categories.     

Fixation disengagement and eye-movement latency

We examined eye-movement latencies to a target that appeared during visual fixation of a stationary stimulus, a moving stimulus, or an extrafoveal stimulus. The stimulus at fixation was turned off either before target onset (gap condition) or after target onset (overlap condition). Consistent with previous research, saccadic latencies were shorter in gap conditions than they were in overlap conditions (the gap effect). In Experiment 1, a gap effect was observed for vergence eye movements. In Experiment 2, a gap effect was observed for saccades directed at a target that appeared during visual pursuit of a moving stimulus. In Experiment 3, a gap effect was observed for saccades directed at a target that appeared during extrafoveal fixation. The present results extend reports of the gap effect for saccadic shifts during visual fixation to (a) vergence shifts during visual fixation, (b) saccadic shifts during smooth visual pursuit, and (c) saccadic shifts during extrafoveal fixation. The present findings are discussed with respect to the incompatible goals of fixation-locking and fixation-shifting oculomotor responses.     

Monkeys (Macaca mulatta and Cebus apella) track, enumerate, and compare multiple sets of moving items

Despite many demonstrations of numerical competence in nonhuman animals, little is known about how well animals enumerate moving stimuli. In this series of experiments, rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella) performed computerized tasks in which they had to enumerate sets of stimuli. In Experiment 1, rhesus monkeys compared two sets of moving stimuli. Experiment 2 required comparisons of a moving set and a static set. Experiment 3 included human participants and capuchin monkeys to assess all 3 species' performance and to determine whether responding was to the numerical properties of the stimulus sets rather than to some other stimulus property such as cumulative area. Experiment 4 required both monkey species to enumerate subsets of each moving array. In all experiments, monkeys performed above chance levels, and their responses were controlled by the number of items in the arrays as opposed to nonnumerical stimulus dimensions. Rhesus monkeys performed comparably to adult humans when directly compared although capuchin performance was lower.     

The role of visual attention in action priming

It has been demonstrated that the task-irrelevant left-right orientation of an object is capable of facilitating left-right-hand responses when the object is orientated towards the responding hand. We investigated the role of attention in this orientation effect. Experiment 1 showed that object orientation facilitates responses of the hand that is compatible with the object's orientation, despite the entire object being irrelevant. However, when a task-relevant fixation point was displayed over the prime object in Experiment 2, the effect was not observed. Together Experiments 1 and 2 suggest that the orientation information of viewed objects primes the action selection processes even when the object is irrelevant, but only when attention is not allocated to a competing stimulus during the prime presentation. Experiment 3 suggested that the elimination of the effect in Experiment 2 could not be attributed to the elimination of an attentional shift to the graspable part of the prime. Finally, Experiment 4 showed that object orientation can evoke an abstract response code, influencing the selection of finger responses.     

The role of visual attention in action priming

It has been demonstrated that the task-irrelevant left–right orientation of an object is capable of facilitating left–right-hand responses when the object is orientated towards the responding hand. We investigated the role of attention in this orientation effect. Experiment 1 showed that object orientation facilitates responses of the hand that is compatible with the object's orientation, despite the entire object being irrelevant. However, when a task-relevant fixation point was displayed over the prime object in Experiment 2, the effect was not observed. Together Experiments 1 and 2 suggest that the orientation information of viewed objects primes the action selection processes even when the object is irrelevant, but only when attention is not allocated to a competing stimulus during the prime presentation. Experiment 3 suggested that the elimination of the effect in Experiment 2 could not be attributed to the elimination of an attentional shift to the graspable part of the prime. Finally, Experiment 4 showed that object orientation can evoke an abstract response code, influencing the selection of finger responses.     

Visual recognition memory enhancement in children through differential outcomes

Objective

The use of differential outcomes has been shown to enhance discriminative learning and face recognition in children and adults. In this study, we further investigated whether the differential outcome procedure (DOP) would also be effective in improving recognition memory for a wide range of stimuli with varying visual complexity (familiar objects, abstract stimuli, and complex scenes) in 5- and 7-year-old children.

Method

Participants viewed a sample stimulus and, after a short (5 s) or a long (15 s) delay, they had to identify the previously seen stimulus among four choice alternatives. In the differential outcomes condition, each sample stimulus was paired with a specific outcome; whereas in the non-differential conditions outcomes were administered randomly. In Experiment 2, we replicated Experiment 1 but in addition we asked participants to perform an articulatory suppression task to prevent verbal rehearsal.

Results

Children showed a greater overall visual delayed recognition when differential outcomes were arranged in both experiments. The type of stimulus being used modulated this effect; a beneficial effect of the differential outcomes training was evident with abstract objects in Experiment 1 and with both, abstract objects and scenes in Experiment 2.     

Simon congruency effects based on stimulus and response numerosity

Three choice reaction time experiments documented a Simon-type congruence effect involving the numbers of stimuli and responses. In Experiment 1 the stimulus consisted of one or two high- or low-pitch tones, and participants were required to respond with one or two taps of a response key depending on stimulus pitch. Responses were faster when the number of tones matched the required number of response taps than when these numbers mismatched. Experiment 2 showed that a weaker version of this effect can also be obtained using visual stimuli, and Experiment 3 showed that the analogous effect can even be obtained, albeit very weakly, with bimodal stimuli. There was also evidence that the number of stimuli affected the rate of emitting the two-tap response. These results indicate that stimulus numerosity is processed automatically to the level at which it can affect the selection and possibly the execution of a varying number of responses.     

Simon congruency effects based on stimulus and response numerosity

Three choice reaction time experiments documented a Simon-type congruence effect involving the numbers of stimuli and responses. In Experiment 1 the stimulus consisted of one or two high- or low-pitch tones, and participants were required to respond with one or two taps of a response key depending on stimulus pitch. Responses were faster when the number of tones matched the required number of response taps than when these numbers mismatched. Experiment 2 showed that a weaker version of this effect can also be obtained using visual stimuli, and Experiment 3 showed that the analogous effect can even be obtained, albeit very weakly, with bimodal stimuli. There was also evidence that the number of stimuli affected the rate of emitting the two-tap response. These results indicate that stimulus numerosity is processed automatically to the level at which it can affect the selection and possibly the execution of a varying number of responses.     

Object individuation in 3-day-old chicks: use of property and spatiotemporal information

Object individuation was investigated in newborn domestic chicks. Chicks' spontaneous tendency to approach the larger group of familiar objects was exploited in a series of five experiments. In the first experiment newborn chicks were reared for 3 days with objects differing in either colour, shape or size. At test, each chick was presented with two groups of events: two objects differing in one property vs. two presentations of the same object. In both cases, all objects involved in the same group of events were sequentially presented and eventually concealed in a different spatial location, and the number of events taking place at each location was equalized. Chicks spontaneously approached the two different objects rather than the single object seen twice. Chicks did not just prefer the more varied set as they did not choose it when the two elements of each group of events were simultaneously presented (Experiment 2). Chicks succeeded when two different objects simultaneously presented were confronted with three identical ones simultaneously presented (Experiment 3), though they failed with sequential presentation of two different objects vs. one object presented three times if they had been familiarized with up to three identical objects (Experiment 4). Chicks instead succeeded if they had been familiarized with objects that were all different from one another (Experiment 5). These young birds thus proved able to use property and spatiotemporal information for object individuation.     

Inhibition of return to occluded objects

Since many visual objects are vulnerable to occlusion, an active process that tracks objects behind occluders confers considerable ecological validity to the visual system. We studied this possibility by testing whether inhibition of return can be observed with occluded objects. In our experiments, two moving objects disappeared or reappeared behind occluders while a cue and a probe were presented. Contrary to the results of a previous study (Tipper, Weaver, Jerreat, & Burak, 1994), responses were consistently delayed for the cued object that was occluded when it was cued (Experiment 1), when it was probed (Experiment 2), or both (Experiment 3). These results suggest that attention can select occluded objects that are out of view. Our findings are in line with prior studies that have demonstrated similar perceptual/attentional effects for occluded objects, as well as for visible objects.     

Development of three-dimensional form perception

In three experiments with infants and one with adults we explored the generality, limitations, and informational bases of early form perception. In the infant studies we used a habituation-of-looking-time procedure and the method of Kellman (1984), in which responses to three-dimensional (3-D) form were isolated by habituating 16-week-old subjects to a single object in two different axes of rotation in depth, and testing afterward for dishabituation to the same object and to a different object in a novel axis of rotation. In Experiment 1, continuous optical transformations given by moving 16-week-old observers around a stationary 3-D object specified 3-D form to infants. In Experiment 2 we found no evidence of 3-D form perception from multiple, stationary, binocular views of objects by 16- and 24-week-olds. Experiment 3A indicated that perspective transformations of the bounding contours of an object, apart from surface information, can specify form at 16 weeks. Experiment 3B provided a methodological check, showing that adult subjects could neither perceive 3-D forms from the static views of the objects in Experiment 3A nor match views of either object across different rotations by proximal stimulus similarities. The results identify continuous perspective transformations, given by object or observer movement, as the informational bases of early 3-D form perception. Detecting form in stationary views appears to be a later developmental acquisition.     

Transport and use of common objects: Influence of weight on action planning

Internal knowledge and visual cues about object's weight play an important role in grasping and lifting objects. It has been shown that both visual cues and internal knowledge might influence movement kinematics and force production depending on action goal (use vs. transport). However, there is little evidence about weight's influence on action planning as reflected by initiation time. In the present study we investigated this issue. In Experiment 1, participants had to grasp light and heavy objects (without moving them) to either use or transport them. In Experiment 2 we asked another group of participants to actually use or transport the same objects. We observed that initiation times were faster for heavy objects than for light objects in both the transport and use tasks, but only in Experiment 2. Thus, weight influenced the planning of use and transport actions, only when the end-goal of the action was really achieved. These data are incompatible with the hypothesis that only use actions are supported by stored object's representations. They rather suggest that in some circumstances, depending of the end-goal of the action and the physical constraints the planning of both use and transport actions are based on stored object representation.     

Perception of partly occluded objects by young chicks

Completion of partly occluded objects is a ubiquitous phenomenon in human visual perception. It is unclear, however, whether it occurs at all in other species: Studies on visual discrimination learning have revealed that animals usually attend to parts and features of the discriminative stimuli rather than to global object properties. We provide here the first demonstration of recognition of partly occluded objects in a bird species, the domestic chickGallus gallus, using the naturalistic setting made available by filial imprinting, a process whereby young birds form attachments to their mothers or some artificial substitute. In Experiment 1, newborn chicks were reared singly with a red cardboard triangle, to which they rapidly imprinted and therefore treated as a social partner. On Day 3 of life, the chicks were presented with pairs of objects composed of either isolated fragments or occluded parts of the imprinting stimulus. Chicks consistently chose to associate with complete or with partly occluded versions of the imprinting object rather than with separate fragments of it. Similarly, in Experiment 2, chicks reared with a partly occluded triangle chose to associate with a complete triangle rather than with a fragmented one, whereas chicks reared with a fragmented triangle chose to associate with a fragmented triangle and not with a complete one. Newborn chicks thus appear to behave as if they could experience amodal completion.     

The neural substrates of action retrieval: An examination of semantic and visual routes to action

We report three PET experiments that examine the neural substrates of the conceptual components of action retrieval. In all three experiments, subjects made action or screen-size decisions to familiar objects presented either as pictures or written words (the names ofthe objects). In Experiment 1, a third task was included, requiring a decision on the real-life size of the stimuli. In Experiment 2, a third stimulus type was included, with action and size decisions also performed on pictures of meaningless novel objects. Finally, in Experiment 3, we changed the response mode from a button press to a more explicit movement made with a “manipulandum”. Based on neuropsychological findings, we predicted that when action responses were made to pictures of familiar or novel objects, relative to words, there would be less activation in semantic regions but greater activation in visual, motor, and perhaps parietal cortices. We found that, action relative to screen-size decisions on both pictures and words activated the left hemisphere temporo-frontal semantic system with activation in the left posterior middle temporal cortex specific to action retrieval (Experiment 1). In addition, action retrieval elicited more activation for (1) words than pictures in areas associated with semantics; and (2) novel objects than words or familiar objects in areas associated with pre-semantic object processing. These results are discussed in the context of semantic and visual routes to action retrieval.     

Asymmetric mislocalization of a visual flash ahead of and behind a moving objectt

When subjects localize a flash relative to another stationary stimulus, the flash appears displaced in the direction of nearby motion signals (position capture; Whitney and Cavanagh, 2000 Nature Neuroscience 3 954-959). Our previous study had suggested that the position capture is larger for a flash presented ahead of a moving stimulus than for a flash behind it (Watanabe et al, 2003 Perception 32 545-559). In the present study, I investigated the spatial asymmetry of position capture. Experiment 1 demonstrated that asymmetric position capture occurs primarily in a moving-object-centered coordinate. Experiment 2 showed evidence that the asymmetric position capture operates after individuation of single visual objects. Finally, experiment 3 demonstrated that, when attention was reduced with a dual-task procedure, the asymmetric position capture increased. These results suggest that the spatial asymmetry of position capture occurs without attention but the spatial bias can be reduced by attention. Therefore, the underlying mechanism for the asymmetric spatial bias may be different from attentive tracking (Cavanagh, 1992 Science 257 1563-1565) and mislocalization during smooth pursuit (Brenner et al, 2001 Vision Research 41 2253-2259).