Independent encoding of colors and shapes from two stimuli

Observers were presented with brief exposures of pairs of colored objects (letters) and asked to report both the color and the shape of each object. Several observers showed strikingly clear evidence of nearly perfect stochastic independence between reports of the four features (two colors and two shapes). For instance, the probability that the shape of a given object could be reported seemed independent of (a) whether the color of the object could be reported and (b) whether features of the other object could be reported. Such stochastic independence is predicted by many parallel-processing models (e.g., Bundesen, 1990). However, the results are difficult to reconcile with simple serial models in which the encoding of one object is completed before the encoding of another object is begun.     

A conflict-based model of color categorical perception: evidence from a priming study

Categorical perception (CP) of color manifests as faster or more accurate discrimination of two shades of color that straddle a category boundary (e.g., one blue and one green) than of two shades from within the same category (e.g., two different shades of green), even when the differences between the pairs of colors are equated according to some objective metric. The results of two experiments provide new evidence for a conflict-based account of this effect, in which CP is caused by competition between visual and verbal/categorical codes on within-category trials. According to this view, conflict arises because the verbal code indicates that the two colors are the same, whereas the visual code indicates that they are different. In Experiment 1, two shades from the same color category were discriminated significantly faster when the previous trial also comprised a pair of within-category colors than when the previous trial comprised a pair from two different color categories. Under the former circumstances, the CP effect disappeared. According to the conflict-based model, response conflict between visual and categorical codes during discrimination of within-category pairs produced an adjustment of cognitive control that reduced the weight given to the categorical code relative to the visual code on the subsequent trial. Consequently, responses on within-category trials were facilitated, and CP effects were reduced. The effectiveness of this conflict-based account was evaluated in comparison with an alternative view that CP reflects temporary warping of perceptual space at the boundaries between color categories.     

Implicit and explicit memory for visual patterns

The article reports an investigation of implicit and explicit memory for novel, visual patterns. Implicit memory was assessed by a speeded perception task, and explicit memory by a four-alternative, forced-choice recognition task. Tests were given either immediately after testing or 7 days later. The results suggest that a single exposure of a novel, nonverbal stimulus is sufficient to establish a representation in memory that is capable of supporting long-lived perceptual priming. In contrast, recognition memory showed significant loss over the same delay. Performance measures in the two tasks showed stochastic independence on the first trial after a single exposure to each pattern. Finally, a specific occurrence of a previously studied item could be retrieved from explicit memory but did not affect the accuracy of perception in the implicit memory test. The results extend the domain of experimental dissociations between explicit and implicit memory to include novel, nonverbal stimuli.     

Not all synaesthetes are created equal: Projector versus associator synaesthetes

In synaesthesia, ordinary stimuli elicit extraordinary experiences. When grapheme-color synaesthetes view black text, each grapheme elicits a photism-a highly specific experience of color. Importantly, some synaesthetes (projectors) report experiencing their photisms in external space, whereas other synaesthetes (associators) report experiencing their photisms "in the mind's eye." We showed that projectors and associators can be differentiated not only by their subjective reports, but also by their performance on Stroop tasks. Digits were presented in colors that were either congruent or incongruent with the synaesthetes' photisms. The synaesthetes named either the video colors of the digits or the colors of the photisms elicited by the digits. The results revealed systematic differences in the patterns of Stroop interference between projectors and associators. Converging evidence from first-person reports and third-person objective measures of Stroop interference establish the projector/ associator distinction as an important individual difference in grapheme-color synaesthesia.     

A method for judging measures of stochastic dependence: further comments on the current controversy.

A large number of reports have been published on stochastic independence between implicit and explicit measures of memory. This is often taken to imply that different memory systems mediate implicit and explicit memory performance. In these cases, stochastic independence is inferred from contingency analysis of overall success rates in two memory tasks when performance in one or both of the tasks is, to a large extent, mediated by factors other than memory. Typically, the difference between performance with studied and nonstudied items is not large in implicit memory tasks. It is argued that this must be taken into account when evaluating the contingency analysis. A method is presented for estimating the relevant joint and conditional probabilities, assuming that the aspects of performance in the two tasks that are related to memory are dependent to the maximum possible extent. The method is applied to a number of published studies, and it is shown that the difference between these estimated probabilities and those given by stochastic independence is too small to allow any conclusion to be drawn about memory systems from contingency analysis of data reported in these studies.     

Consumer preferences for color combinations: An empirical analysis of similarity-based color relationships

In this paper, we examine aesthetic color combinations in a realistic product self-design task using the NIKEiD online configurator. We develop a similarity-based model of color relationships and empirically model the choice likelihoods of color pairs as a function of the distances between colors in the CIELAB color space. Our empirical analysis reveals three key findings. First, people de-emphasize lightness and focus on hue and saturation. Second, given this shift in emphasis, people generally like to combine colors that are relatively close or exactly match, with the exception that some people highlight one signature product component by using contrastive color. This result is more consistent with the visual coherence perspective than the optimal arousal perspective on aesthetic preference. Third, a small palette principle is supported such that the total number of colors used in the average design was smaller than would be expected under statistical independence.     

Short-term memory in the pigeon: stimulus-response associations

Three pigeons pecked for food in two experiments in which each trial consisted of two phases: a study and a test phase. The study phase in Experiment I consisted of two stimulus-response pairs presented successively. Each pair consisted of the illumination of a left or right key (the stimulus) and a peck on the lighted side key (the response). The study phase in Experiment II consisted of three such pairs presented successively. A retention interval, varied between 0.1 and 4.0 sec, separated the study phase from the test phase. The test phase of a trial began with the illumination of the center key by one of two (Experiment I) or three (Experiment II) colors. This color was the same as the stimulus element of one of the pairs in the study phase. A reinforcer was presented if a subject then emitted the response element of the indicated stimulus-response pair. The results provide information on the conditions that enable a pigeon to remember the responses most recently emitted in the presence of various stimuli. The results suggest an account of the maintenance of behavior that is temporally noncontiguous with reinforcement.     

Formation of the sameness-difference concept by Japanese monkeys from a small number of color stimuli

Japanese monkeys were trained to form the sameness-difference concept. In Experiment 1, four monkeys were trained with two colors to discriminate matching stimulus pairs from nonmatching pairs by reinforcing only lever-pressing responses to matching pairs with a variable-interval schedule. Three monkeys showed successful transfer of this discrimination to two new colors, thus demonstrating that some Japanese monkeys are able to form this relational concept from a minimum number of stimuli. In Experiment 2, two monkeys were trained, in a Yes/No procedure with three colors, to press one lever under matching pairs and another lever under nonmatching pairs. Poor transfer performances to three new colors suggest that simultaneously establishing two different response patterns to matching and nonmatching pairs is ineffective in forming the concept. In Experiment 3, the amount of transfer to three new colors after mastering a standard three-color matching-to-sample task was compared with that of a modified task in which correct responses were reinforced with a within-trial variable-interval schedule. All three monkeys showed greater transfer with the modified procedure. The results suggest that the variable-interval schedule adopted within trials is effective in forming the sameness-difference concept.     

Stochastic independence in the recognition/identification paradigm

Abstract

Experiments in which subjects study a set of items and then take two successive tests, a recognition test followed by a test of implicit retrieval of the same items (e.g. Tulving, Schacter, & Stark, 1982), have typically yielded data showing stochastic independence between the tests. Ostergaard (1992) has suggested that the procedure for assessing such independence should include an evaluation of the data against a model that assumes maximal dependence between the components of the test attributable to the study episode. In applying his Maximum Memory Dependence model to the published data, however, Ostergaard inexplicably used test-primed data for baseline measures, rather than non-primed data, and erroneously concluded that there was no clear evidence for independence. In this article, we show that when the standard baseline measures are used, the results of many experiments demonstrate stochastic independence.     

Discrimination of structure: I. Implications for connectionist theories of discrimination learning

In each of 4 experiments animals were given a structural discrimination task that involved visual patterns composed of identical features, but the spatial relations among the features were different for reinforced and nonreinforced trials. In Experiment 1 the stimuli were pairs of colored circles, and pigeons were required to discriminate between patterns that were the mirror image of each other. A related task was given to rats in Experiment 2. Subjects solved these discriminations. For Experiment 3, some pigeons were given a discrimination similar to that used in Experiment 1, which they solved, whereas others received a comparable task but with 3 colored circles present on every trial, which they failed to solve. The findings from Experiment 3 were replicated in Experiment 4 using different patterns. The results are difficult to explain by certain connectionist theories of discrimination learning, unless they are modified to take account of the way in which compound stimuli are structured.     

Color-function categories that prime infants to use color information in an object individuation task

There is evidence for developmental hierarchies in the type of information to which infants attend when reasoning about objects. Investigators have questioned the origin of these hierarchies and how infants come to identify new sources of information when reasoning about objects. The goal of the present experiments was to shed light on this debate by identifying conditions under which infants’ sensitivity to color information, which is slow to emerge, could be enhanced in an object individuation task. The outcome of Experiment 1 confirmed and extended previous reports that 9.5-month-olds can be primed, through exposure to events in which the color of an object predicts its function, to attend to color differences in a subsequent individuation task. The outcomes of Experiments 2-4 revealed age-related changes in the nature of the representations that support color priming. This is exemplified by three main findings. First, the representations that are formed during the color-function events are relatively specific. That is, infants are primed to use the color difference seen in the color-function events to individuate objects in the test events, but not other color differences. Second, 9.5-month-olds can be led to form more abstract event representations, and then generalize to other colors in the test events if they are shown multiple pairs of colors in the color-function events. Third, slightly younger 9-month-olds also can be led to form more inclusive categories with multiple color pairs, but only when they are allowed to directly compare the exemplars in each color pair during the present events. These results shed light on the development of categorization abilities, cognitive mechanisms that support color-function priming, and the kinds of experiences that can increase infants’ sensitivity to color information.     

Comprehension of "absence" by an African Grey parrot: Learning with respect to questions of same/different

An African Grey parrot, Alex, learned to report on the absence or presence of similarity and difference between two objects. Alex was shown pairs of objects that were (a) totally dissimilar, (b) identical, or (c) similar or different with respect to one of three attributes (color, shape, or material). In the first two cases, he responded to the respective queries of “What's same?” or “What's different?” with the vocalization “none,” and in the third case he responded with the appropriate category label (“color,” “shape,” or “mah-mah” [matter]). His accuracy was 80.9% to 83.9% for pairs of familiar objects not used in training and 72.5% to 78.4% for pairs whose colors, shapes, and materials were unfamiliar. The data provide evidence that this parrot's abilities are comparable to those of mammals that have been trained to report on the presence or absence of objects or features of objects.     

Evidence against Rank-Dependent Utility Theories: Tests of Cumulative Independence,Interval Independence,Stochastic Dominance,and Transitivity

This study tests between two modern theories of decision making. Rank- and sign-dependent utility (RSDU) models, including cumulative prospect theory (CPT), imply stochastic dominance and two cumulative independence conditions. Configural weight models, with parameters estimated in previous research, predict systematic violations of these properties for certain choices. Experimental data systematically violate all three properties, contrary to RSDU but consistent with configural weight models. This study also tests whether violations of stochastic dominance can be explained by violations of transitivity. Violations of transitivity may be evidence of a dominance detecting mechanism. Although some transitivity violations were observed, most choice triads violated stochastic dominance without violating transitivity. Judged differences between gambles were not consistent with the CPT model. Data were not consistent with the editing principles of cancellation and combination. The main findings are interpreted in terms of coalescing, the principle that equal outcomes can be combined in a gamble by adding their probabilities. RSDU models imply coalescing but configural weight models violate it, allowing configural weighting to explain violations of stochastic dominance and cumulative independence.     

Rats’ anticipation of current and future trial outcomes in the ordered RNR/RNN serial pattern task

In the ordered RNR/RNN serial pattern task, rats often reduce their running speeds on trial 2 less within the RNR than within the RNN series. Initially, investigators (Capaldi, 1985; Capaldi et al., 1983) considered this trial 2 differential speed effect evidence for rats’ anticipation of inter-trial outcomes within each series. Later findings, however, suggest that this effect reflects some generalization of the ordinal position of trial 3 (Burns et al., 1986) or its similar runway cues during trial 2 (Capaldi et al., 1999). To test these generalization hypotheses, we made trial 2 more distinct from trial 3 in each series by forcing rats to alternate runways in a T-maze only on the last trial rather than on trial 2 in each series in Experiment 1, or by forcing rats to alternate runways between trials rather than to run down the same runway on all trials within each series in Experiment 2. Although enhancing the distinctiveness between these trials reduced the trial 2 differential speed effect, extensive training failed to eliminate it. Therefore, this residual difference between trial 2 speeds could reflect rats’ anticipation of trial 3 outcomes during trial 2 as originally proposed by Capaldi (1985) Experiment 3 was designed to determine whether we could enhance rats’ final trial outcome expectancies during trial 2 by making different trial 2 choices distinctive cues for each trial 3 outcome. The trial 2 speed effect was greater when rats were forced to alternate over all trials only within one of the series than when they were sometimes forced to do so in either series. Post-training probe tests revealed that both series position and the relevant within-series runway events contributed to this enhanced anticipation of trial 3 outcomes.     

Associative independence revisited: competition between conflicting associations can be resolved or even reversed in one trial

In one type of association-memory paradigm, after studying pairs of the form AB, AC, participants must recall both B and C in response to A. Counterintuitively, yet often replicated, recall probabilities of B and C are typically uncorrelated (“associative independence”). This face-value independence is now understood to reflect a negative correlation due to AB and AC competing, approximately offset by a positive correlation produced by subject- and item-variability. The outcome might vary with stimulus material; for noun-pairs, and with a single study trial per pair, AB and AC have been found to be positively correlated. We replicated the positive correlation between AB and AC for noun-pairs, but this did not differ from the correlation expected for independent memory tests, suggesting that for noun pairs, AB and AC are independent on average. In Experiment 2, participants instructed to form separate images for AB and AC again produced an independence pattern, but participants instructed to combine AB and AC into an integrative image produced a facilitation pattern. Thus, the relationship between AB and AC varies, and can be influenced by study strategy. Association-memory models may need to accommodate a diverse range of AB–AC relationships, and studies that build on AB/AC learning may need to consider whether AB/AC start out with a competitive, facilitatory or independent relationship.     

Is a Pink Cow Still a Cow? Individual Differences in Toddlers' Vocabulary Knowledge and Lexical Representations

When a toddler knows a word, what does she actually know? Many categories have multiple relevant properties; for example, shape and color are relevant to membership in the category banana . How do toddlers prioritize these properties when recognizing familiar words, and are there systematic differences among children? In this study, toddlers viewed pairs of objects associated with prototypical colors. On some trials, objects were typically colored (e.g., Holstein cow and pink pig); on other trials, colors were switched (e.g., pink cow and Holstein‐patterned pig). On each trial, toddlers were directed to find a target object. Overall, recognition was disrupted when colors were switched, as measured by eye movements. Moreover, individual differences in vocabularies predicted recognition differences: Toddlers who say fewer shape‐based words were more disrupted by color switches. “Knowing” a word may not mean the same thing for all toddlers; different toddlers prioritize different facets of familiar objects in their lexical representations.     

Retrieval independence between parts and wholes in successive recognition tasks

Participants studied AB word pairs and completed three recognition tests. In one recognition test each A word was presented with two distractors that did not appear on the study list. In another recognition test each B word was presented with two distractors that did not appear on the study list. In a third recognition test an AB target was presented with two distractors composed of words not on the study list. Six different groups of participants each performed the recognition tests in a different order, so that all possible orders were tested. Recognition of the A, B, and AB targets for a given study pair were independent of each other when single-word recognition preceded double-word recognition. There was almost complete independence in the reverse order. Even when recognition judgements were restricted to those for which the participants were most confident, there was independence of recognition among the three tests. A pair recognition test served as an additional study trial for the individual words; however, the reverse was not the case. All of these results were predicted by a single three-parameter mathematical model derived from the hypothesis that single-word and double-word targets had independent representations in memory.     

Deriving relations at multiple levels of complexity following minimal instruction: A demonstration

Recommendations for achieving generalized instructional outcomes often overlook the capacity for generative learning for most verbally competent humans. Four children (ages 5–8) participated in this project. In Study 1, we provided decontextualized discrete trial teaching to establish arbitrary relations between colors, pictures of characters, and researcher motor actions. All participants engaged in derivative responding, providing evidence of relational framing. Subsequently, we demonstrated that, with no additional instruction, these derivatives contributed to effective action within a socially valid context (i.e., Candyland gameplay). Study 2 extended the demonstration by teaching frames of opposition. Following teaching, all participants engaged in novel and contextually appropriate responding that entailed the derivation of both coordination and opposition between untrained stimuli. This outcome demonstrates how teaching simple relations can result in learning that manifests at higher levels of complexity (i.e., relational networking), providing some evidence that there can be socially valid benefits to decontextualized discrete trial instruction.     

Retrieval independence between parts and wholes in successive recognition tasks

Participants studied AB word pairs and completed three recognition tests. In one recognition test each A word was presented with two distractors that did not appear on the study list. In another recognition test each B word was presented with two distractors that did not appear on the study list. In a third recognition test an AB target was presented with two distractors composed of words not on the study list. Six different groups of participants each performed the recognition tests in a different order, so that all possible orders were tested. Recognition of the A, B, and AB targets for a given study pair were independent of each other when single-word recognition preceded double-word recognition. There was almost complete independence in the reverse order. Even when recognition judgements were restricted to those for which the participants were most confident, there was independence of recognition among the three tests. A pair recognition test served as an additional study trial for the individual words; however, the reverse was not the case. All of these results were predicted by a single three-parameter mathematical model derived from the hypothesis that single-word and double-word targets had independent representations in memory.     

The threshold for successiveness

In Experiment 1, three stimuli were presented on each trial; the second and third were simultaneous. Ss said which of the three they saw first and then made a different second guess. Second guesses were correct more often than chance when first guesses were wrong, contradicting the predictions of a psychological moment theory. Psychometric functions are inconsistent with a theory which holds that Ss can order their perceptions and that errors result from lack of correspondence between this order and that of the stimuli. In Experiment 2, two pairs of stimuli, each simultaneous or successive, were presented on each trial, the interval between their onsets varying, and Ss guessed whether each was successive. A moment-like cyclic process affecting the perception of successive stimuli should raise the correlation between responses when both pairs were successive and beginning at the same time; this was not found.