Of monkeys and men: Impatience in perceptual decision-making

For decades sequential sampling models have successfully accounted for human and monkey decision-making, relying on the standard assumption that decision makers maintain a pre-set decision standard throughout the decision process. Based on the theoretical argument of reward rate maximization, some authors have recently suggested that decision makers become increasingly impatient as time passes and therefore lower their decision standard. Indeed, a number of studies show that computational models with an impatience component provide a good fit to human and monkey decision behavior. However, many of these studies lack quantitative model comparisons and systematic manipulations of rewards. Moreover, the often-cited evidence from single-cell recordings is not unequivocal and complimentary data from human subjects is largely missing. We conclude that, despite some enthusiastic calls for the abandonment of the standard model, the idea of an impatience component has yet to be fully established; we suggest a number of recently developed tools that will help bring the debate to a conclusive settlement.     

When aggressive individuals see the world more accurately: the case of perceptual sensitivity to subtle facial expressions of anger

Previous research has suggested that aggressive individuals exhibit a bias to perceive nonangry expressions as angry. Another line of thinking, however, posits that aggression is a learned response to hostile environments and should be linked to social-cognitive skills suited to such environments. If so, aggressive individuals may exhibit greater perceptual sensitivity to subtle facial cues of anger. Three studies were conducted to test this proposal. In them, participants' ability to discriminate between subtly different intensities of facial anger was tested. Aggressive participants generally displayed greater perceptual sensitivity to subtle cues of facial anger. This pattern could not be explained in terms of response bias and was specific to angry expressions. The results thus support the idea that aggression is associated with social-cognitive skills rather than bias and ineptitude.     

Imagination, language, and the perceptual world: a post-analytic phenomenology

This paper seeks to integrate analytic philosophy and phenomenology. It does so through an approach generated, specifically, in relation to imagination and its cognitive significance. As an Introduction, some reservations about existing phenomenological approaches to imagination—in the work of Sartre and Edward S. Casey—are considered. It is argued that their introspective psychological approach needs to be qualified through a more analytic orientation that determines essence, initially, on the basis of public discourse concerning the term ‘imagination.’ Part One then articulates this orientation through an ‘analytic reduction’ that identifies imagination’s essence in public discourse as thought in its quasi-sensory mode. Part Two offers a sustained phenomenological investigation of this essence, and identifies four major intrinsic features. On the basis of this, Part Three shows how imagination is implicated, centrally, in the capacity to acquire language. In Conclusion the proceeding arguments are defended against possible objections, and a final key summarizing argument is formulated to show that imagination must be regarded, also, as necessary to perception and its capacity to articulate a world. The paper ends with a few thoughts on the further potential of post-analytic phenomenology.     

Multiple perceptual strategies used by macaque monkeys for face recognition

Successful integration of individuals in macaque societies suggests that monkeys use fast and efficient perceptual mechanisms to discriminate between conspecifics. Humans and great apes use primarily holistic and configural, but also feature-based, processing for face recognition. The relative contribution of these processes to face recognition in monkeys is not known. We measured face recognition in three monkeys performing a visual paired comparison task. Monkey and humans faces were (1) axially rotated, (2) inverted, (3) high-pass filtered, and (4) low-pass filtered to isolate different face processing strategies. The amount of time spent looking at the eyes, mouth, and other facial features was compared across monkey and human faces for each type of stimulus manipulation. For all monkeys, face recognition, expressed as novelty preference, was intact for monkey faces that were axially rotated or spatially filtered and was supported in general by preferential looking at the eyes, but was impaired for inverted faces in two of the three monkeys. Axially rotated, upright human faces with a full range of spatial frequencies were also recognized, however, the distribution of time spent exploring each facial feature was significantly different compared to monkey faces. No novelty preference, and hence no inferred recognition, was observed for inverted or low-pass filtered human faces. High-pass filtered human faces were recognized, however, the looking pattern on facial features deviated from the pattern observed for monkey faces. Taken together these results indicate large differences in recognition success and in perceptual strategies used by monkeys to recognize humans versus conspecifics. Monkeys use both second-order configural and feature-based processing to recognize the faces of conspecifics, but they use primarily feature-based strategies to recognize human faces.     

The limits of perceived magnitude: Comparison among individuals and among perceptual continua

Two models of perceived magnitude that focus on the concept of dynamic range (DR) for sensory systems are summarized and compared. The first asserts that, whereas the size of DR varies physically from one perceptual continuum to another, all are subjectively equal. The other asserts that, for any given continuum, whereas the size of DR varies over individual observers, the subjective range does not.A test of the second model is reported for perceived effort for a range of loads on a bicycle ergometer. Both DR and judgmental (magnitude estimation) range estimates were obtained for 30 subjects. The former exhibited the expected variability over subjects, but there was no support for the predicted invariance of the latter. However, it is concluded, first, that the finding constitutes disconfirming evidence for the second model only if it is assumed that magnitude estimates are proportional to perceived magnitude, an issue which itself remains in dispute, and second, that the testability of the second model is doubtful unless a measure can be identified that is a stateable function of perceived magnitude.     

Face processing in humans and new world monkeys: the influence of experiential and ecological factors

This study tests whether the face-processing system of humans and a nonhuman primate species share characteristics that would allow for early and quick processing of socially salient stimuli: a sensitivity toward conspecific faces, a sensitivity toward highly practiced face stimuli, and an ability to generalize changes in the face that do not suggest a new identity, such as a face differently oriented. The look rates by adult tamarins and humans toward conspecific and other primate faces were examined to determine if these characteristics are shared. A visual paired comparison (VPC) task presented subjects with either a human face, chimpanzee face, tamarin face, or an object as a sample, and then a pair containing the previous stimulus and a novel stimulus was presented. The stimuli were either presented all in an upright orientation, or all in an inverted orientation. The novel stimulus in the pair was either an orientation change of the same face/object or a new example of the same type of face/object, and the stimuli were shown either in an upright orientation or in an inverted orientation. Preference to novelty scores revealed that humans attended most to novel individual human faces, and this effect decreased significantly if the stimuli were inverted. Tamarins showed preferential looking toward novel orientations of previously seen tamarin faces in the upright orientation, but not in an inverted orientation. Similarly, their preference to look longer at novel tamarin and human faces within the pair was reduced significantly with inverted stimuli. The results confirmed prior findings in humans that novel human faces generate more attention in the upright than in the inverted orientation. The monkeys also attended more to faces of conspecifics, but showed an inversion effect to orientation change in tamarin faces and to identity changes in tamarin and human faces. The results indicate configural processing restricted to particular kinds of primate faces by a New World monkey species, with configural processing influenced by life experience (human faces and tamarin faces) and specialized to process orientation changes specific to conspecific faces.     

Attention and perceptual priming in the perceptual identification task

Prior research indicates that manipulations of attention during encoding sometimes affect perceptual implicit memory. Two hypotheses were investigated. One proposes that manipulations of attention affect perceptual priming only to the extent that they disrupt stimulus identification. The other attributes reduced priming to the disruptive effects of distractor selection. The role of attention was investigated with a variant of the Stroop task in which participants either read words, identified their color, or did both. Identifying the color reduced priming even when the word was also overtly identified. This result held regardless of whether color and word were presented as a single object (Experiments 1 and 2) or as separate objects (Experiment 4). When participants read and identified a color, the overt order of the responses did not matter; both conditions reduced priming relative to reading alone (Experiment 3). The results provide evidence against the stimulus-identification account but are consistent with the distractor-selection hypothesis.     

Multidimensional scaling: Combining observations when individuals have different perceptual structures

The usual methods of combining observations to give interpoint distance estimates based on interstimulus differences are shown to lead to a distortion of the stimulus configuration unless all individuals in a group perceive the stimuli in perceptual spaces which are essentially the same. The nature of the expected distortion is shown, and a method of combining individual distance estimates which produces only a linear deformation of the stimulus configuration is given.The work reported in this paper forms part of that which was undertaken towards a Ph.D. Degree in the University of Western Australia under the supervision of Dr. John Ross. The author was killed in a road accident before the completion of his Ph.D. The final revision of this paper was made by Ross, to whom enquiries and requests for reprints should be addressed.     

Research on effects of color reversal on the visual perceptual and visuomotor performances of spastic cerebral palsied and other exceptional individuals

Research pertaining to the effects of color-reversal (black and white) on the visual perceptual and visuomotor performances of spastic cerebral-palsied children and other exceptional individuals was examined. In general, evidence to date suggests that spastic cerebral-palsied children show significant improvement in visuomotor and visual perceptual performance with the color-reversal of the standard black-on-white figure-ground relationship in stimulus and response materials of standardized tests.     

On the relation between decision rules and perceptual representation in multidimensional perceptual categorization

This article examines the relation between changing categorization decision rules and the nature of the underlying perceptual representation. Observers completed a matching task that required them to adjust the length and orientation of a single line stimulus until they perceived it to "match" a second line stimulus (Alfonso-Reese, 1996, 1997). The same observers then completed four categorization tasks with the same stimuli. Data from the matching task were used to estimate a perceptual representation for each stimulus and observer. Three hypotheses regarding potential interactions between categorization decision rules and perceptual representation were examined. One assumed that there was no interaction between decision rules and perceptual representation. The second assumed that linear categorization rules affect the perceptual representation differently from nonlinear categorization rules. The third assumed that dimensional integration rules affected the perceptual representation differently from decision rules that require the observer to set a criterion along one stimulus dimension while ignoring the other; this is referred to as decisional selective attention. The results suggested that (1) the matching task perceptual representation provided a good account of the categorization data, (2) decisional selective attention affected the perceptual representation differently from decisional integration, and (3) decisional selective attention generally decreased the perceptual variability along the attended dimension.     

Attention to combined attention in new world monkeys (Cebus apella, Saimiri sciureus)

Co-orientation by capuchin (Cebus apella) and squirrel (Saimiri sciureus) monkeys in response to familiar humans abruptly switching the direction of their visual attention was recorded. Co-orientation occurred more frequently overall in capuchins than squirrel monkeys. Capuchins showed a tendency to habituate within trials involving consecutive attention switches performed by 2 different people, whereas squirrel monkeys co-oriented more when the 2nd attention switch was by a 2nd actor. These results suggest variable attention-processing abilities in New World monkeys, including differences in summation of attention by others.     

Human adults and human infants show a "perceptual magnet effect" for the prototypes of speech categories, monkeys do not

Many perceptual categories exhibit internal structure in which category prototypes play an important role. In the four experiments reported here, the internal structure of phonetic categories was explored in studies involving adults, infants, and monkeys. In Experiment 1, adults rated the category goodness of 64 variants of the vowel i parallel on a scale from 1 to 7. The results showed that there was a certain location in vowel space where listeners rated the i parallel vowels as best instances, or prototypes. The perceived goodness of i parallel vowels declined systematically as stimuli were further removed from the prototypic i parallel vowel. Experiment 2 went beyond this initial demonstration and examined the effect of speech prototypes on perception. Either the prototypic or a nonprototypic i parallel vowels was used as the referent stimulus and adults' generalization to other members of the category was examined. Results showed that the typicality of the speech stimulus strongly affected perception. When the prototype of the category served as the referent vowel, there was significantly greater generalization to other i parallel vowels, relative to the situation in which the nonprototype served as the referent. The notion of a perceptual magnet was introduced. The prototype of the category functioned like a perceptual magnet for other category members; it assimilated neighboring stimuli, effectively pulling them toward the prototype. In Experiment 3, the ontogenetic origins of the perceptual magnet effect were explored by testing 6-month-old infants. The results showed that infants' perception of vowels was also strongly affected by speech prototypes. Infants showed significantly greater generalization when the prototype of the vowel category served as the referent; moreover, their responses were highly correlated with those of adults. In Experiment 4, Rhesus monkeys were tested to examine whether or not the prototype's magnet effect was unique to humans. The animals did not provide any evidence of speech prototypes; they did not exhibit the magnet effect. It is suggested that the internal organization of phonetic categories around prototypic members is an ontogenetically early, species-specific, aspect of the speech code.     

Congruity and the perceptual comparison task

The effects of congruity between comparatives and the relative magnitudes of to-be-compared stimuli were investigated in six perceptual comparison experiments. Experiments 1-5 failed to obtain congruity effects in purely perceptual tasks even when subjects had extensive practice with a relatively small stimulus set. Experiment 6 obtained a congruity effect with perceptual stimuli but only when the stimuli were described as representing real-world objects. All of the results indicated that congruity effects occur only in tasks that include major symbolic or memorial components; a review of the perceptual comparison literature reveals consistent support for this position. These findings are discussed in terms of expectancy and semantic coding interpretations of the congruity effect.     

Consolidation and interference in the perceptual memory system

Previous verbal/memory studies have indicated that perceptual processes continue to occur after the stimulus is terminated. The present study investigated whether a blank period after a nonverbal stimulus would function to strengthen or consolidate the sensory trace in memory. A “delayed-comparison task” of recognition memory for pitch was employed in two experiments. The results indicated that a blank interval after the tone to be remembered increased the memory strength of that tone when the tone’s duration was brief (.2 sec). However, an empty interval after a tone with a longer duration (.5 sec) did not affect memory performance. Memory strength also decreased over time during a retroactive interval tone. A storage-interference model described the quantitative results accurately.     

Attention and the measurement of perceptual learning

Novel and familiar letters were presented to Ss under conditions which controlled momentary attention states. The latencies of letter matching for the novel and familiar letters did not differ when Ss were expecting the particular letters which were presented. However, latencies to the two types of letters differed significantly when Ss were not expecting the particular letters which were presented. Additional exposures significantly reduced this difference, thereby generating a perceptual learning curve in terms of response latency. The main findings were interpreted in terms of a model of perceptual processing which involves mechanisms for hierarchical coding, selective attention, and automatic processing.     

Comparison and contrast in perceptual categorization

People categorized pairs of perceptual stimuli that varied in both category membership and pairwise similarity. Experiments 1 and 2 showed categorization of 1 color of a pair to be reliably contrasted from that of the other. This similarity-based contrast effect occurred only when the context stimulus was relevant for the categorization of the target (Experiment 3). The effect was not simply owing to perceptual color contrast (Experiment 4), and it extended to pictures from common semantic categories (Experiment 5). Results were consistent with a sign-and-magnitude version of N. Stewart and G. D. A. Brown's (2005) similarity-dissimilarity generalized context model, in which categorization is affected by both similarity to and difference from target categories. The data are also modeled with criterion setting theory (M. Treisman & T. C. Williams, 1984), in which the decision criterion is systematically shifted toward the mean of the current stimuli.