New Caledonian crows use tools for non-foraging activities

Tool use is of great interest for cognitive research, largely because it can be particularly revealing about the underlying information processing mechanisms. Tool use that is inflexible or requires extensive experience to change, and that is only addressed towards specific targets such as food, is not likely to reflect unusual or particularly complex cognition. On the contrary, if tools are employed flexibly and for a variety of innovative purposes, then conventional combinations of inherited predispositions and associative learning are challenged and interesting questions emerge. Since New Caledonian crows (Corvus moneduloides) are especially adept at using and making tools for food extraction, we decided to examine their ability to generalise this to other contexts. We recorded how five pairs of New Caledonian crows interacted with novel objects that were not associated with food. We observed eight occasions in which the first contact with the novel object was mediated by a tool, suggesting that the function of the tool was for exploration. This is the first report of non-foraging tool use in New Caledonian crows, and it implies that the cognitive operations controlling tool-oriented behaviour in this species are more general than previously thought.     

客体及其位置记忆的眼动研究(中文)

In this paper we briefly describe preliminary data from two experiments that we have carried out to investigate the relationship between visual encoding and memory for objects and their locations within scenes. In these experiments, we recorded participants′ eye movements as they viewed a photograph of a cubicle with 12 objects positioned pseudo-randomly on a desk and shelves. After viewing the photograph, participants were taken to the actual cubicle where they undertook two memory tests. Participants were asked to identify the 12 target objects(from the photograph)presented amongst 12 distractors. They were then required to place each of the objects in the location that they occupied in the photograph. These tests assessed participants′ memory for identity of the objects and their locations. In Experiment 1, we assessed the influence of the encoding period and the test delay on object identity and location memory. In Experiment 2 we manipulated scanning behaviour during encoding by "boxing"some of the objects in the photo. We showed that using boxes to change eye movement behaviour during encoding directly affected the nature of memory for the scene. The results of these studies indicate a fundamental relationship between visual encoding and memory for objects and their locations. We explain our findings in terms of the Visual Memory Model(Hollingworth & Henderson, 2002).     

Lightness constancy and illumination discounting

Contrary to the implication of the term "lightness constancy", asymmetric lightness matching has never been found to be perfect unless the scene is highly articulated (i.e., contains a number of different reflectances). Also, lightness constancy has been found to vary for different observers, and an effect of instruction (lightness vs. brightness) has been reported. The elusiveness of lightness constancy presents a great challenge to visual science; we revisit these issues in the following experiment, which involved 44 observers in total. The stimuli consisted of a large sheet of black paper with a rectangular spotlight projected onto the lower half and 40 squares of various shades of grey printed on the upper half. The luminance ratio at the edge of the spotlight was 25, while that of the squares varied from 2 to 16. Three different instructions were given to observers: They were asked to find a square in the upper half that (i) looked as if it was made of the same paper as that on which the spotlight fell (lightness match), (ii) had the same luminance contrast as the spotlight edge (contrast match), or (iii) had the same brightness as the spotlight (brightness match). Observers made 10 matches of each of the three types. Great interindividual variability was found for all three types of matches. In particular, the individual Brunswik ratios were found to vary over a broad range (from .47 to .85). That is, lightness matches were found to be far from veridical. Contrast matches were also found to be inaccurate, being on average, underestimated by a factor of 3.4. Articulation was found to essentially affect not only lightness, but contrast and brightness matches as well. No difference was found between the lightness and luminance contrast matches. While the brightness matches significantly differed from the other matches, the difference was small. Furthermore, the brightness matches were found to be subject to the same interindividual variability and the same effect of articulation. This leads to the conclusion that inexperienced observers are unable to estimate both the brightness and the luminance contrast of the light reflected from real objects lit by real lights. None of our observers perceived illumination edges purely as illumination edges: A partial Gelb effect ("partial illumination discounting") always took place. The lightness inconstancy in our experiment resulted from this partial illumination discounting. We propose an account of our results based on the two-dimensionality of achromatic colour. We argue that large interindividual variations and the effect of articulation are caused by the large ambiguity of luminance ratios in the stimulus displays used in laboratory conditions.     

Predicting Election Outcomes from Positive and Negative Trait Assessments of Candidate Images

Conventional wisdom, and a growing body of behavioral research, suggests that the nonverbal image of a candidate influences voter decision making. We presented subjects with images of political candidates and asked them to make four trait judgments based solely on viewing the photographs. Subjects were asked which of the two faces exhibited more competence, attractiveness, deceitfulness, and threat, which are arguably four of the most salient attributes that can be conveyed by faces. When we compared our subjects' choices to the actual election outcomes, we found that the candidates chosen as more likely to physically threaten the subjects actually lost 65% of the real elections. As expected, our findings support the conclusions of Todorov, Mandisodza, Goren, and Hall (2005 ) by showing a positive correlation between the competence judgments and the real election outcomes. Surprisingly, attractiveness was correlated with losing elections, with the effect being driven by faces of candidates who looked politically incompetent yet personally attractive. Our findings have implications for future research on negative political communication, as they suggest that both threatening first impressions and fleeting impressions of attractiveness can harm a candidate's electoral chances.