Domestic dogs (Canis familiaris) use a physical marker to locate hidden food

Dogs can use the placement of an arbitrary marker to locate hidden food in an object-choice situation. We tested domestic dogs (Canis familiaris) in three studies aimed at pinning down the relative contributions of the human’s hand and the marker itself. We baited one of two cups (outside of the dogs’ view) and gave the dog a communicative cue to find the food. Study 1 systematically varied dogs’ perceptual access to the marker placing event, so that dogs saw either the whole human, the hand only, the marker only, or nothing. Follow-up trials investigated the effect of removing the marker before the dog’s choice. Dogs used the marker as a communicative cue even when it had been removed prior to the dog’s choice and attached more importance to this cue than to the hand that placed it although the presence of the hand boosted performance when it appeared together with the marker. Study 2 directly contrasted the importance of the hand and the marker and revealed that the effect of the marker diminished if it had been associated with both cups. In contrast touching both cups with the hand had no effect on performance. Study 3 investigated whether the means of marker placement (intentional or accidental) had an effect on dogs’ choices. Results showed that dogs did not differentiate intentional and accidental placing of the marker. These results suggest that dogs use the marker as a genuine communicative cue quite independently from the experimenter’s actions.     

Apes' use of iconic cues in the object-choice task

In previous studies great apes have shown little ability to locate hidden food using a physical marker placed by a human directly on the target location. In this study, we hypothesized that the perceptual similarity between an iconic cue and the hidden reward (baited container) would help apes to infer the location of the food. In the first two experiments, we found that if an iconic cue is given in addition to a spatial/indexical cue - e.g., picture or replica of a banana placed on the target location - apes (chimpanzees, bonobos, orangutans, gorillas) as a group performed above chance. However, we also found in two further experiments that when iconic cues were given on their own without spatial/indexical information (iconic cue held up by human with no diagnostic spatial/indexical information), the apes were back to chance performance. Our overall conclusion is that although iconic information helps apes in the process of searching hidden food, the poor performance found in the last two experiments is due to apes' lack of understanding of the informative (cooperative) communicative intention of the experimenter.     

Can wild common marmosets (Callithrix jacchus) solve the parallel strings task?

Patterned string tasks are a test of perceptual capacity and the understanding of means-end connections. Primates can solve complex forms of this task in laboratories. However, this may not indicate the level of such cognition that is commonly employed in the wild, where decision-making time is often short and distractions such as predator avoidance and competition between conspecifics are often prevalent. The current study tests whether wild common marmosets (Callithrix jacchus) can successfully complete the simplest form of the patterned string task, parallel strings, while in their natural environment. Although 12 out of 13 marmosets could successfully complete the task, in previous laboratory-based studies on primates, the errors at this task by all primate species tested were consistently lower than in the present study. This is probably explained by the added difficulties imposed by the natural setting of the task in the present study, exemplified by a significant increase in observed vigilance behaviour by subject animals prior to attempts at the task that were unsuccessful. The undertaking of such tasks by common marmosets in situ probably provides a more reasonable representation of the levels of cognitive capacity expressed by this species in the wild than do laboratory-based studies of the task.     

Use or misuse of the selection task? Rejoinder to Fiddick,Cosmides, and Tooby

Sperber, Cara, and Girotto (Cognition 52 (1995) 3) argued that, in Wason's selection task, relevance-guided comprehension processes tend to determine participants' performance and pre-empt the use of other inferential capacities. Because of this, the value of the selection task as a tool for studying human inference has been grossly overestimated. Fiddick, Cosmides, and Tooby (Cognition 77 (2000) 1) argued against Sperber et al. that specialized inferential mechanisms, in particular the "social contract algorithm" hypothesized by Cosmides (Cognition 31 (1989) 187), pre-empt more general comprehension abilities, making the selection task a useful tool after all. We rebut this argument. We argue and illustrate with two new experiments, that Fiddick et al. mix the true Wason selection task with a trivially simple categorization task superficially similar to the Wason task, yielding methodologically flawed evidence. We conclude that the extensive use of various kinds of selection tasks in the psychology of reasoning has been quite counter-productive and should be discontinued.     

Task switching: a PDP model

When subjects switch between a pair of stimulus-response tasks, reaction time is slower on trial N if a different task was performed on trial N - 1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on "switch trials" can be slowed by an extended response selection process which results from (a) persisting, inappropriate states of activation and inhibition of task-controlling representations; and (b) associative learning, which allows stimuli to evoke tasks sets with which they have recently been associated (as proposed by Allport & Wylie, 2000). The model provides a good fit to a large body of empirical data, including findings which have been seen as problematic for this explanation of switch costs, and shows similar behavior when the parameters are set to random values, supporting Allport and Wylie's proposal.     

How do children coordinate simultaneous upper and lower extremity tasks? The development of dual motor task coordination

When performing simultaneous clapping with walking or galloping, adults adopt coupled, consistent and stable dual motor task coordination; do developmental trends in this coordination exist? In this study, we measured and compared coupling characteristics, consistency across trials and variability of phasing in 4-, 6-, 8-, and 10-year-olds (n=44) as they also performed the same dual motor task. For walk/clap, children adopted specific coupling patterns like adults by 8 years and with the same consistency by 10 years. Across age, children became less variable in clap and step movements separately and as coupled together. In the gallop/clap, children did not resemble adults in coupling patterns by 10 years but all measures were becoming more consistent across age. We discuss dual motor task coordination as a function of age and task complexity using a "dynamic" perspective within a developmental context.     

Primacy and recency effects in task analyses: Preliminary results

Performance for three independent living tasks were examined via task analyses. Given the relatively small sample size (n = 56) of individuals with intellectual and developmental disabilities, we simulated 1000 replications based upon observed results using Monte Carlo techniques. The results of the current study suggest that: (1) adaptive behavior was more related to task performance than IQ; and (2) after statistically controlling for adaptive behavior, task performance was influenced by the first step. Task performance appear to be over-estimated with the inclusion of the first step.     

视剥夺及视剥夺学习后Jun样蛋白在雏鸡两侧半球中不同表达的研究

该实验利用免疫组化技术,在已有实验的基础上进一步观察比较了左眼视剥夺及单眼学习后,Ｊｕｎ样蛋白在雏鸡两侧半球ＨＶ和ＬＰＯ中表达的差异。实验结果表明：１．视剥夺２、２４、４８、７２小时后观测到Ｊｕｎ样蛋白在左、右半球ＨＶ和ＬＰＯ中的表达逐渐增高,并且于视剥夺４８小时表达到达峰值。同时仅在视剥夺２小时后观测到两半球ＬＰＯ中Ｊｕｎ样蛋白的表达存在差异,在其余各视剥夺时程中两侧半球的ＬＰＯ、ＨＶ中Ｊｕｎ样蛋白的表达均无显著差异。２．视剥夺２小时和２４小时后均在学习后７０分钟组中观测到Ｊｕｎ样蛋白在左、右半球的ＨＶ和ＬＰＯ中表达的显著升高,而在视剥夺２小时学习后１０分钟只观测到左半球ＨＶ和ＬＰＯ中Ｊｕｎ样蛋白表达的显著升高,在视剥夺２４小时学习后１０分钟中仅观测到左半球ＬＰＯ中Ｊｕｎ样蛋白的显著升高。同时也仅在视剥夺２小时学习后１０分钟观测到两侧半球ＨＶ、ＬＰＯ中Ｊｕｎ样蛋白表达的显著性差异。３．无论单纯视剥夺组还是单眼学习组,各组同侧半球中ＬＰＯＪｕｎ样蛋白的表达显著高于ＨＶ的Ｊｕｎ样蛋白的表达现象在视剥夺４８小时后消失。     

THE EFFECTS OF INTERSPERSED MAINTENANCE TASKS ON ACADEMIC PERFORMANCE IN A SEVERE CHILDHOOD STROKE VICTIM

We examined the effects of task-sequencing variables on the academic performance of an 8-year-old severe stroke victim. Within a multiple baseline design, previously acquired (maintenance) task trials were systematically interspersed at designated points in treatment among new (acquisition) task trials. The results showed improvements in both academic responding and subjective ratings of motivation in each of four treated areas (spelling, reading, word-finding, and memory). Social validation data obtained from standardized school placement examinations suggested marked improvement in a variety of related areas of academic functioning. Results suggest that children suffering severe strokes may be capable of learning more than has previously been suspected, and that behavioral treatments may improve such children's functioning.