Bantams (Gallus gallus domesticus) also perceive a reversed Zöllner illusion

Although pigeons have been shown to be susceptible to several size and length illusions, other avian species have not been tested intensively for illusory perception. Here we report how bantams perceive the Zöllner figure, in which parallel lines look nonparallel due to short crosshatches superimposed on the lines. Watanabe et al. (Cognition 119:137–141, 2011) showed that pigeons, like humans, perceived parallel lines as nonparallel but that the orientation of subjective convergence was opposite to that of humans. We trained three bantams to peck at the narrower (or wider) of the two gaps at the end of a pair of nonparallel lines. After adapting them to target lines with randomly oriented crosshatches (which result in no apparent illusion to humans), we tested the bantams’ responses on randomly inserted probe trials, in which crosshatches that should induce the standard Zöllner-like illusion for humans replaced the randomly oriented ones. The results suggested bantams, like pigeons, perceive a reversed Zöllner illusion.     

I acknowledge your help: capuchin monkeys’ sensitivity to others’ labor

Our society is sustained by wide-ranging cooperation. If individuals are sensitive to others’ gains and losses as well as the amount of labor, they can ensure future beneficial cooperative interaction. However, it is still an open question whether nonhuman primates are sensitive to others’ labor. We asked this question in tufted capuchin monkeys in an experimental food-sharing situation by comparing conditions with labor by two participants equalized (Equal labor condition) or unequalized (Unequal labor condition). The operator monkey pulled the drawer of one of the two food containers placed between two monkeys, each containing a food for him/herself and another for the recipient monkey. The recipient received either high- or low-value food depending on the operator’s choice, whereas the operator obtained the same food regardless of his/her choice. In Unequal labor condition, the operator first had to pull the handle of the board to which the containers were glued and then pull the drawer of one of the containers, while the recipient received food with no labor. In Equal labor condition, the recipient had to pull the handle of the board so that the operator could operate a container. Results showed that operators chose the high-value food container for recipients more often than when the recipient was absent only in Equal labor condition. This suggests that capuchin monkeys are sensitive to others’ labor and actively give food to a partner who has helped them to complete a task.     

How do keas (<Emphasis Type="Italic">Nestor notabilis</Emphasis>) solve artificial-fruit problems with multiple locks?

Keas, a species of parrots from New Zealand, are an interesting species for comparative studies of problem solving and cognition because they are known not only for efficient capacities for object manipulation but also for explorative and playful behaviors. To what extent are they efficient or explorative, and what cognitive abilities do they use? We examined how keas would solve several versions of artificial-fruit box problems having multiple locks. After training keas to remove a metal rod from over a Plexiglas lid that had to be opened, we exposed the birds to a variety of tasks having two or more locks. We also introduced a preview phase during which the keas had extended opportunity to look at the tasks before the experimenter allowed the birds to solve them, to examine whether the preview phase would facilitate the birds’ performance on the tasks. In a large number of tests, the keas showed a strong trend to solve the tasks with no positive effect of previewing the tasks. When the tasks became complex, however, the keas corrected inappropriate responses more quickly when they had had chance to preview the problems than when they had not. The results suggest that the keas primarily used explorative strategies in solving the lock problems but might have obtained some information about the tasks before starting to solve them. This may reflect a good compromise of keas’ trial-and-error tendency and their good cognitive ability that result from a selection pressure they have faced in their natural habitat.     

Do birds (pigeons and bantams) know how confident they are of their perceptual decisions?

Rhesus monkeys are known to recognize confidence about their immediate perceptual and cognitive decisions by using a betting procedure (Son and Kornell in The missing link in cognition: origins of self-reflective consciousness. Oxford University Press, New York, pp 296–320, 2005; Kornell et al. in Psychol Sci 18:64–71, 2007). In this report, we examined whether this ability is shared in two avian species (pigeons and bantams) in order to know how widespread this metacognitive ability is among animals. We trained pigeons and bantams to search for a differently colored disk (target) among others (distracters) displayed on a touch-sensitive monitor. In test, the subjects were required to choose one of two confidence icons, “risk” and “safe”, after the visual search. A peck at the “risk” icon after a correct response in the visual search (i.e., a peck at the target) was reinforced by food and light, while that after an incorrect response (i.e., a peck at a distracter) resulted in a timeout. A peck at the “safe” icon was always reinforced by food and light, or by light only, regardless of the visual search result. The percentages of “safe” choices after incorrect responses were higher than after correct responses in all six pigeons and two of three bantams. This behavior generalized to novel stimuli in some subjects, and even to a novel line-classification task in a pigeon. These results suggest that these two distantly related avian species have in common a metacognitive ability that allows them to recognize confidence about their immediate perceptual decisions.     

Pigeons perceive a reversed Zöllner illusion

Pigeons are susceptible to several size and length illusions, but in some cases the bias has been shown to be opposite to that seen in humans. To further investigate how their perceptual system works, we asked how pigeons perceive orientation illusions. We used the Zöllner illusion, in which parallel lines look non-parallel due to series of short crosshatches superimposed on the lines. First, we trained six birds to peck at the narrower (or wider) of the two gaps at the end of a pair of non-parallel target lines. After adapting the subjects to target lines with randomly oriented crosshatches (which result in no illusion at least to humans), we tested the pigeons’ responses on randomly inserted probe trials, in which crosshatches that should induce the standard Zöllner-like illusion for humans replaced the random-oriented ones. The results suggested that pigeons do perceive an illusion from Zöllner figures, but in the direction opposite to that of humans. We propose that pigeons, contrary to humans, may assimilate the two lines of different orientations (each main line and crosshatch), which results in underestimation of acute angles, and this in turn may lead to a reversed Zöllner illusion. Such assimilation dominance appears consistent with previous reports obtained for line length and size illusions in this species.     

Hemodynamic and electrophysiological connectivity in the language system: Simultaneous near-infrared spectroscopy and electrocorticography recordings during cortical stimulation

We applied near-infrared spectroscopy (NIRS) and electrocorticography (ECoG) recordings during cortical stimulation to a temporal lobe epilepsy patient who underwent subdural electrode implantation. Using NIRS, changes in blood concentrations of oxyhemoglobin (HbO(2)) and deoxyhemoglobin (HbR) during cortical stimulation of the left language areas were measured in each hemisphere. NIRS revealed that 2Hz stimulation with 5mA produced no significant hemodynamic changes in either hemisphere. By contrast, 50Hz stimulation elicited significant increases in both HbO(2) and HbR at the stimulation site. Furthermore, with 50Hz stimulation of the left superior temporal gyrus, the increases in HbO(2) and HbR were observed not only at the stimulation site but also concurrently at the left inferior frontal gyrus. This suggests the existence of functional connectivity in the language system. The present study demonstrates that simultaneous NIRS and ECoG studies during cortical stimulation allow a novel analysis of cerebral connectivity.     

Cultural influences on the relation between pleasant emotions and unpleasant emotions: Asian dialectic philosophies or individualism-collectivism?

The present study examined the hypothesis that Asian cultures' dialectical way of thinking influences emotion reports. A dialectical way of thinking sees emotions of the opposite valence (e.g., happy, sad) as compatible with each other. In contrast, Western philosophy considers these emotions to be in conflict with each other. We examined correlations between frequency estimates of pleasant emotions (FPE) and frequency estimates of unpleasant emotions (FUE) in Asian, non-Asian collectivistic, and Western cultures. As predicted, FPE-FUE correlations were less negative in Asian cultures than in other cultures. We also observed a tendency for the culture effect to be moderated by gender. The strongest negative correlation was obtained for women in non-Asian cultures.