The still-face paradigm in Latin American mother-child dyads at 2 and 3 years: Effects of socioeconomic status and temperament.

The still-face paradigm (SFP) is a common method in infancy used to assess emotion regulation and interactions when an adult (typically the caregiver) abruptly stops a positive interaction with a child and switches to a more neutral affect. The effect of this paradigm has been studied in different countries and age ranges, but research in Latin America and with toddlers (e.g., 2-3 years old) of different socioeconomic backgrounds is scarce. The current study analyzed caregiver-child interactions in this novel sample, to analyze the possibility of generalization of the typical response of this paradigm (i.e., less positive affect, reduced gaze, and more negative affect in children when parent affect changes). The sample consisted of 114 caregiver-child dyads from low to middle socioeconomic status (SES) (children's Mage = 26.61 months, SD = 6.73, range = 18-36; 61 girls). The SFP modified version (i.e., on the floor and with a series of standardized toys), the temperament Early Childhood Behavior Questionnaire adapted for Argentina, and an SES scale were used. The typical SFP response was observed in Latin American children. In addition, older children and children with higher SES exhibited better general regulation, and there were weak associations with temperament. For gender differences, boys demonstrated more aggressive behaviors at Phase II. Results from this study suggest that children's response to this paradigm is an unconditional response to the lack of social reinforcers and is only partially associated with social and individual variables.

Frustración, temperamento y vulnerabilidad social en bebés: estudio comparativo / Frustration, temperament and social vulnerability in babies: a comparative study

Resumen Antecedentes: la frustración se define como las respuestas del organismo que se desencadenan cuando existe una discrepancia negativa entre un incentivo esperado con el que realmente se recibe. Estas situaciones provocan respuestas conductuales, emocionales y neurofisiológicas análogas a las que ocurren con la presentación de estímulos aversivos o su anticipación. Existen investigaciones en bebés, pero pocos sobre sus asociaciones con diferencias individuales y ambientales y ninguno en población argentina. Objetivos: asociar la frustración, el temperamento y la vulnerabilidad social en una muestra de infantes. Metodología: se realizó un estudio asociativo-comparativo con una situación observacional estructurada donde se evaluaron a 22 bebés de 10 a 14 meses durante una tarea de frustración y su relación con el temperamento a través del Cuestionario de Conducta Infantil (IBQ-VSF) pertenecientes a dos extractos sociales evaluados con una ficha sociodemográfica. Resultados: se halló que a mayor extroversión, menor manipulación del objeto; y a mayor esfuerzo de control, menor fue la respuesta de morder, y viceversa. No se encontraron diferencias significativas en función del nivel socioeconómico. Conclusiones: se discutieron los resultados en función de la teoría de la frustración y las limitaciones del estudio, incluyendo recomendaciones para futuras investigaciones.

Abstract Background: Frustration is defined as the body's responses that are triggered when there is a negative discrepancy between an expected incentive and the one actually received. These situations elicit behavioral, emotional and neurophysiological responses analogous to those that occur with aversive stimuli or their anticipation. There is research on babies, but few on the associations with individual and environmental differences and none on the Argentine population. Objectives: To associate frustration, temperament and social vulnerability in a sample of infants. Method: A comparative associative study was carried out using a structured observation technique where frustration and its relationship with temperament were evaluated in 22 babies aged 10 to 14 months through the infant behavior questionnaire-revised very short form (IBQ-R VSF). The study population belonged to two social strata according to a sociodemographic record. Results: An inverse correlation was found between extroversion and manipulation of objects, and between effortful control and biting response. No significant differences were identified based on the socioeconomic level. Conclusions: The results were discussed taking into account the frustration theory, the study limitations and the recommendations for future research.

Attachment Styles, Personality, and Frustration Intolerance.

The objective of the present study was to evaluate the relationships between attachment styles, personality traits, and their effects on frustration intolerance (FI) in a sample of 300 adults. The Argentine Attachment Styles Scale, the Eysenck Revised Personality Questionnaire (EPQ-RA), and the Frustration Intolerance Scale (EIF) was used. In the two Full Latent Variable Models developed, it was determined that neuroticism and avoidant attachment had the greatest mediating effects on FI. Avoidant attachment stood out for its mediating effect on anxious attachment. These two factors were found to explain a considerable percentage of neuroticism and, as a consequence, the four dimensions of FI. It is concluded that it is necessary to reinterpret certain concepts of neuroticism and study them from a perspective that starts from attachment theory.

Emociones y frustración en bebés: el temperamento y la vulnerabilidad social como factores moduladores / Emotions and frustration in babies: temperament and social vulnerability as modulating factors

Las emociones son consideradas como mecanismos que se configuran a largo del tiempo para adaptarse a las demandas del medio ambiente, procurando de esta forma la supervivencia. Una de ellas es la frustración que se define como las respuestas del organismo que se desencadenan cuando existe una discrepancia negativa entre un incentivo esperado con el que realmente recibe. Estas situaciones provocan respuestas conductuales, emocionales y neurofisiológicas análogas a las que ocurren con la presentación de estímulos aversivos o su anticipación, tales como la ansiedad, el miedo, el estrés y el dolor nocioceptivo. El objetivo del presente artículo es: a) presentar los principales modelos teóricos de la emoción y frustración, su desarrollo y sus relaciones con factores individuales (temperamento) y ambientales (pobreza), y b) hacer un relevamiento de la bibliografía existente sobre los efectos de la frustración en bebés de hasta un año. Se encontró que el temperamento contribuye a los niveles de emoción y frustración expresados por los infantes. Son necesarios más trabajos para evaluar la influencia del ambiente y en un segundo momento, realizar intervenciones que puedan aumentar la tolerancias a la frustración(AU)

Emotions are considered as mechanisms that are configured over time for conflicts to the demands of the environment, thus seeking survival. Frustration is defined as an organism response that is triggered when there is a negative discrepancy between an expected incentive and the one that actually receives. These situations provoke behavioral, emotional and neurophysiological responses analogous to those that occur with the presentation of aversive stimuli or their anticipation, stories such as anxiety, fear, stress and nocioceptive pain. The objective of this article is: a) to present the main theoretical models of emotion and frustration, their development and their relationships with individual (temperament) and environmental (poverty) factors, and b) to survey the existing bibliography on the effects of frustration in babies up to one year old. Temperament and vulnerability were found to have the levels of emotion and frustration expressed by infants. However, it will be necessary to carry out more studies to decrease the contradictory results and generate, in a second moment, those that can increase the levels of this ability(AU)

Regulation During the Second Year: Executive Function and Emotion Regulation Links to Joint Attention, Temperament, and Social Vulnerability in a Latin American Sample.

Although a growing body of work has established developing regulatory abilities during the second year of life, more work is needed to better understand factors that influence this emerging control. The purpose of the present study was to examine regulation capacities in executive functions (i.e., EF or cognitive control) and emotion regulation (i.e., ER or control focused on modulating negative and sustaining positive emotions) in a Latin American sample, with a focus on how joint attention, social vulnerability, and temperament contribute to performance. Sixty Latin American dyads of mothers and children aged 18 to 24 months completed several EF tasks, a Still-Face Paradigm (SFP) to examine ER (Weinberg et al., 2008), and the Early Social Communication Scale to measure joint attention (Mundy et al., 2003). Parents completed the Early Childhood Behavior Questionnaire Very Short Form to measure temperament (ECBQ-VS, Putnam et al., 2010) and the Social Economic Level Scale (SES) from INDEC (2000). Results revealed the typical responses expected for toddlers of this age in these EF tasks and in the SFP. Also, we found associations between EF and ER and between non-verbal communication related to monitoring infants' attention to objects (i.e., responding to joint attention) and initiation of pointing (e.g., pointing and showing of an object while the child alternates his gaze to an adult) with EF. Regarding social factors, family differences and type of housing contribute to regulation. For temperament, effortful control was associated with both regulatory capacities. Finally, only age predicted EF. These results suggest that many patterns regarding the development of these abilities are duplicated in the first months of life in a Latin American sample while further highlighting the importance of considering how the environment and the individual characteristics of infants may associate to these regulatory abilities, which is particularly relevant to developing public policies to promote their optimal development.

Intolerancia a la frustración y estrategias cognitivas de regulación emocional en la predicción de la agresividad / Frustration intolerance and cognitive strategies of emotional regulation in the prediction of aggressiveness

Resumen La conducta agresiva constituye un problema que afecta a los individuos y a la so ciedad. El Modelo de Agresión General integra un conjunto de variables que influyen en la pro babilidad de exhibir una conducta agresiva entre las cuales está la regulación emocional y la frustración. Esta investigación evalúa las relaciones entre la regulación emocional cognitiva y la intolerancia a la frustración. A 419 sujetos adultos se les administraron la Escala de Intoleran cia a la Frustración, la Escala de Regulación Emocional Cognitiva y el Cuestionario de Agresión. Se hallaron relaciones positivas en la mayoría de las estrategias desadaptativas cognitivas de regulación emocional y relaciones negativas entre la mayoría de las estrategias cognitivas adap tativas de regulación emocional con la conducta agresiva, y relaciones positivas entre todas las dimensiones de la intolerancia a la frustración y la conducta agresiva. El Análisis de Regresión Múltiple muestra que las variables que producen un cambio significativo en la agresividad son la catastrofización y culpar a otros, así como la intolerancia a la frustración referida a derechos. Mediante path análisis se verificó que estas tres variables mencionadas permiten explicar un 41% de la variabilidad en la agresividad.

Abstract Aggressive behavior is a problem that affects individuals and society. The General Aggression Model integrates a set of variables that influence the probability of exhibiting aggressive behavior, among which is emotional regulation and frustration. This research assesses the relationships between cognitive emotional regulation and frustration intolerance. A total of 419 adult subjects were administered the Frustration Intolerance Scale, the Cognitive Emotional Regulation Scale and the Aggression Questionnaire. Positive relationships were found in most of the maladaptive cognitive emotional regulation strategies and negative re lationships between most of the adaptive cognitive emotional regulation strategies with the aggressive behavior, and positive relationships between all the dimensions of the frustration intolerance and the aggressive behavior. The Multiple Regression Analysis shows that the vari ables that produce a significant change in aggressiveness are catastrophization and blaming others, as well as the frustration intolerance referring to rights. By means of path analysis, it was verified that these three variables can explain 41% of the variability in aggressiveness.

Adaptación Argentina de la "Escala de intolerancia a la frustración" / Argentinean adaptation of the Frustration Intolerance Scale

La "Escala de intolerancia a la frustración" (EIF; Harrington, 2005) permite evaluar una serie de creencias que promueven la intolerancia a las molestias, el esfuerzo, la injusticia y las emociones incómodas. A pesar de la importancia de este instrumento, no existe una versión en español de la EIF. En este trabajo se evaluó la equivalencia de una traducción de la EIF mediante un panel de expertos. Posteriormente, mediante análisis factorial confirmatorio (n= 799) se concluyó que la EIF posee una estructura multidimensional de cuatro factores: Intolerancia emocional, Derecho, Intolerancia a la incomodidad y Logro. Sin embargo, debieron eliminarse 11 ítems, lo cual afectó la consistencia interna de algunas dimensiones. También se examinó la invarianza del instrumento considerando la edad, sexo y nivel educativo de los participantes, obteniéndose pruebas de validez de criterio correlacionando la EIF con los niveles de autoestima. Los resultados psicométricos fueron aceptables, aunque se identificaron algunas limitaciones a considerar antes de utilizar a nivel profesional. Este trabajo inaugura futuros estudios sobre IF en países de habla española

The Intolerance to Frustration Scale (IFS, Harrington, 2005) assesses a series of beliefs that promote intolerance to annoyance, exertion, injustice and uncomfortable emotions. Despite the importance of this instrument, there is no Spanish version of the IFS. In this work, the equivalence of a translation from thecIFS was assessed by a panel of experts. Subsequently, by means of confirmatory factorial analysis (n= 799) it was concluded that the IFS has a multidimensional structure of four factors: Emotional Intolerance, Right, Intolerance to Discomfort and Achievement. However, 11 items had to be removed, which affected the internal consistency of some dimensions. The invariance of the instrument was also examined considering the age, sex and educational level of the participants, and evidence of validity as obtained by correlating the IFS with self-esteem levels. Psychometric results were acceptable, although some limitations should be addressed before the scale is used professionally in Spanish-speaking countries

Change in the hedonic value of an aversive stimulus in the presence of a pre-exposed odor.

Rats exhibit a sensitive period from the time of birth until postnatal day 10 during which they develop preferences for odors even if those odors are paired with a moderately aversive stimulus. It is still unknown whether pre-exposure to an odor produces alterations on intake responses of basic tastants, and on other patterns that indicate a change in the hedonic value of reward, such as nipple grasping behavior. The current study assessed the effect of pre-exposure to an odor immediately after birth on intake responses of appetitive and aversive tastants. The objectives were to assess if 3-hour-old rats adjust their behaviors to obtain different values of appetitive and aversive rewards in the presence of a familiar odor. Specifically we wanted to determine whether the intake of saccharin or quinine, administered through the artificial nipple, increases in the presence of the familiar odor. Results showed that 3-hour-old rats differentially respond to two different concentrations of saccharin and two concentrations of quinine. In the presence of the pre-exposed odor newborn rats increased intake and grasp responses to the artificial nipple containing quinine. This effect disappeared with a higher concentration of quinine. These results suggest that the pre-exposed odor generated a change in the hedonic value of the aversive reward.

Ontogeny of consummatory successive negative contrast in rats.

Consummatory successive negative contrast (cSNC) occurs when organisms repeatedly exposed to a high-magnitude reward are suddenly given a low-magnitude reward. This results in a significant reduction in the consumption of the devalued reinforcer, at a level even below that of a group which had been always exposed to the low-magnitude reinforcer. A scarcity of animal studies assessed the expression of this phenomenon during early development. Three experiments assessed age of cSNC onset in preweanling rats. Percent body weight gained (%BWG) and taste reactions associated with reinforcement devaluation were measured. A reduction in %BWG and a significant increase in emission of aversive hedonic behaviors, indicative of cSNC, occurred on postnatal day 18 (PD 18; Experiments 1 and 2), but not on PD 14 or PD 17 (Experiments 3a and 3b). The neurobiological mechanisms underlying these effects and theoretical implications are discussed.

Efecto de contraste sucesivo negativo en la valoración emocional de imágenes / Successive negative contrast effect on the emotional evaluation of images

Se presentan dos experimentos para estudiar el efecto de la reducción del valor de incentivo sobre las respuestas de tiempo de observación y valoración de la emocionalidad de las imágenes, mediante una escala Likert. En ambos estudios un grupo de sujetos observó una serie de fotografías del Sistema Internacional de Imagen Afectiva (International Affective Picture System; IAPS) clasificadas como placenteras de alta activación (fase de precambio) y luego, placenteras de baja activación (fase de postcambio, Grupo Experimental, GE). Otro grupo observó en ambas fases solamente las imágenes placenteras de baja activación (Grupo Control, GC). No hubo efectos en el tiempo de observación de las imágenes pero sí en su valoración emocional. Durante la fase de post-cambio el GE evaluó las imágenes de baja activación como menos emocionales que el GC. El Experimento 2 replica el resultado cuando se interpone una tarea distractora entre cada ensayo de presentación de las imágenes. Estos resultados indican que la valoración afectiva de las imágenes está modulada por efectos de contraste negativo y que su mecanismo es de origen central (AU)

Two experiments were presented in which the International Affective Picture System (IAPS) was used to study the effect of the incentive value downshift upon the observation time and emotional valuation responses in humans. One group observed pleasant slides of high arousal (pre-shift phase) and then pleasant slides of low arousal (post-shift phase, Experimental Group, GE). The Control Group (GC) observed pleasant slides of low arousal in both phases. There was not an effect on the observation time measure, but a successive negative contrast (SNC) effect was found in the emotional valuation measure. During the post-shift phase, the GE evaluated the slides as less emotional than the GC. These results indicate that the affective evaluation of the images is modulated by negative contrast effect (AU)

Consummatory suppression due to incentive downshift is not a consequence of enhanced search behavior.

Rats shifted from 32% to 4% sucrose solution consume less from the 4% solution than rats that experience only the 4% solution. This consummatory suppression, a phenomenon known as consummatory successive negative contrast (cSNC), is accompanied by an increase in other behaviors such as rearing, nose-down locomotion, ambulation, sampling new sources and grooming. Despite a large body of studies on the cSNC, it remains to be determined whether reduced consumption is part of the direct response to the reward downshift or a byproduct of the increase in alternative competing behaviors. The objective of the present study was to determine if consummatory suppression would occur when most competing behaviors are prevented from occurring. Rats were trained either with 32% or 4% sucrose solution for ten days in restrainers that limited almost all movement. On the next five days, all subjects received the 4% sucrose solution and a robust suppression in drinking in the downshifted animals was observed. These results suggest that consummatory suppression is a direct consequence of incentive downshift and not a byproduct of the increase in competing behaviors.

Frustration behaviors in domestic dogs.

During extinction a previously learned behavior stops being reinforced. In addition to the decrease in the rate of the instrumental response, it produces an aversive emotional state known as frustration. This state can be assimilated with the fear reactions that occur after aversive stimuli are introduced at both the physiological and behavioral levels. This study evaluated frustration reactions of domestic dogs (Canis familiaris) during a communicative situation involving interactions with a human. The task included the reinforcement and extinction of the gaze response toward the experimenter's face when the dogs tried to obtain inaccessible food. The dog's frustration reactions during extinction involved an increase in withdrawal and side orientation to the location of the human as well as lying down, ambulation, sniffing, and vocalizations compared with the last acquisition trial. These results are especially relevant for domestic dog training situations in which the extinction technique is commonly used to discourage undesirable behaviors.

Effect of Neonatal Clomipramine Treatment on consummatory Successive Negative Contrast

La administración neonatal de clomipramina (CLI) produce alteraciones fisiológicas, neuroendocrinas y comportamentales en las ratas adultas, que son similares a las observadas en los modelos animales de depresión. En el Contraste Sucesivo Negativo consumatorio (CSNc), las ratas que recibieron una solución de sacarosa al 32%, consumen menos de una solución de sacarosa al 4%, que los animales que siempre recibieron la solución 4%. Este modelo de devaluación del incentivo produce en los animales una reacción emocional similar al miedo y la ansiedad. En el presente trabajo, estudiamos si el tratamiento neonatal con CLI altera la respuesta de CSNc en ratas adultas. Los hallazgos del presente trabajo sugieren que el tratamiento neonatal con un antidepresivo podría generar un aumento en la tolerancia a la frustración en animales adultos. Los animales a los que se les administró neonatalmente CLI presentaron una recuperación más rápida en el CSNc, que los animales controles sin tratamiento neonatal. Este resultado puede explicarse por una alteración del eje Hipotálamo-Pituitario-Adrenal (HPA), por un deterioro del sistema serotoninérgico, por la formación de una baja expectativa durante la fase de pre-cambio, o por una combinación de estos factores(AU)

Neonatal administration of clomipramine (CLI) produces physiological, neuroendocrinal and behavioral abnormalities in rats when they reach adulthood, which are similar to those observed in animal models of depression. In consummatory successive negative contrast (cSNC), rats that have had experience drinking 32% sucrose solution drink significantly less 4% sucrose solution than rats that have drunk only 4% solution. It triggers an aversive-emotional reaction similar to fear or anxiety. We studied whether neonatal treatment with CLI alters the cSNC’s response in adult rats. The findings of the present work suggest that the neonatal treatment with an antidepressive could generate an increase tolerance to frustration in adult animals. CLI rats showed a faster recovery from the cSNC than control animals, which may be explained by an alteration of the Hypothalamic- Pituitary-Adrenal axis (HPA), a serotonergic system deficit, a low expectative formation during pre-shift phase, or a combination of all these factors(AU)

Effects of testosterone administration and gonadectomy on incentive downshift and open field activity in rats.

Previous research showed that the effects of incentive downshift in male rats are attenuated by a pretrial opportunity to ejaculate. Because ejaculation raises testosterone (T) levels and has anxiolytic-like effects in male rats, the present experiments were designed to assess the role of T and gonadectomy (GDX) on two situations involving incentive downshift. In consummatory successive negative contrast, a downshift from 32% to 4% sucrose leads to consummatory suppression. T alleviates such suppression (Experiment 1), but GDX does not affect it (Experiment 3). In consummatory extinction, animals are downshifted from 32% sucrose to an empty sipper tube. T enhances consummatory extinction (Experiment 2), but GDX does not affect it (Experiment 4). In agreement with published results, T increases (Experiment 2) and GDX reduces (Experiment 4) activity in the central area of an open field, thus behaviorally validating these manipulations. The results are discussed in terms of the anxiolytic-like properties of androgen hormones.

Effects of pretraining treatment with testosterone on successive and anticipatory negative contrast.

Previous research indicated that the suppression of consummatory behavior that follows incentive downshift in male rats is attenuated by testosterone (T) administration during training. The present experiments were designed to assess the role of pretraining T administration on two incentive contrast situations in consummatory behavior: successive negative contrast (cSNC) and anticipatory negative contrast (cANC). In cSNC (Experiment 1), a downshift from 32% to 4% sucrose leads to behavioral suppression relative to an unshifted, 4% sucrose condition (the cSNC effect). Pretraining T administration enhanced consummatory behavior directed at 4% sucrose, without affecting behavior directed at 32% sucrose. This effect obscured a reduction in the cSNC effect by the T treatment that was only detected when a proportional measure of behavior was used. In cANC (Experiment 2), groups received access to two bottles per day separated by a short midtrial interval. Consumption of 4% sucrose is suppressed when the second bottle offers 32% sucrose, relative to 4% sucrose (the cANC effect). Pretraining T did not affect the cANC effect, known to be insensitive to treatment with anxiolytics. These results suggest an anxiolytic-like effect of testosterone in adjustment to incentive downshifts.

Efecto de renovación en el condicionamiento y sus implicancias clínicas / Renewal effect on conditioning and its clinical implications

El efecto de renovación se refiere a la reaparición de una respuesta condicionada por un cambio de contexto entre la extinción y su evaluación. Este fenómeno tiene relevancia a nivel teórico, ya que evidencia que en la extinción el aprendizaje no se destruye y a nivel aplicado, porque los tratamientos psicológicos que implican un proceso de extinción se realizan en general en un contexto diferente a aquel en el que se pone a prueba su eficacia y la respuesta puede reaparecer por el efecto de renovación. Este artículo revisa los procedimientos en los que se estudió la renovación de la respuesta, tanto del condicionamiento clásico como del instrumental, así como aquellos tratamientos que evitan su ocurrencia.

Renewal effect refers to the reappearance of a conditioned response by a context change between extinction and testing. This phenomenon holds relevance at a theoretical level since it shows that, in extinction, learning does not go under. Also at an applied level, because psychological treatments that relay on extinction processes are done generally at a different context than that where they are put to test and therefore the response can reappear due to the renewal effect. This article reviews the procedures among which the effects of both classic and instrumental conditioning were studied as well as those treatments that preventthem from occurring.

Breed differences in dogs' (Canis familiaris) gaze to the human face.

Domestic dogs (Canis familiaris) have been submitted to a vast process of artificial selection and to date, there are hundreds of breeds that differ in their physical and behavioral features. In addition, dogs possess important skills to communicate with humans. Previous evidence indicates that those abilities are related to the domestication process and are modulated by instrumental learning processes. Very few studies, however, have evaluated breed differences in the use and learning of interspecific communicative responses. In Study 1 Retrievers, German Shepherds and Poodles were compared in the acquisition and extinction of their gaze toward the human face, in a conflict situation involving food within sight but out of reach. The groups did not differ in the acquisition of the response, but throughout the extinction phase Retrievers gazed to the human significantly more than the other groups. In Study 2, similar results were obtained in a test without any previous explicit training. These results suggest that these three major popular breeds differ in gazing to humans in a communicative situation.

Ethanol facilitates consummatory extinction.

Rats given access to an empty sipper tube after having obtained 32% sucrose in the same situation undergo extinction of consummatory behavior (cE). Ethanol (0.75 and 1g/kg, i.p.) accelerated cE when administered before the second extinction session. The effect was not attributable to increased activity or state-dependent reduction in consummatory behavior. These data are discussed in the context of research on the effects of ethanol on behavioral assays involving incentive downshifts.

Communication between domestic dogs (Canis familiaris) and humans: dogs are good learners.

Communication involves a wide range of behaviours that animals emit in their daily lives and can take place between different species, as is the case of domestic dogs (Canis familiaris) and humans. Dogs have shown to be successful at following human cues to solve the object choice task. The question is what are the mechanisms involved in these communicative abilities. This article presents a review of studies about the communicative capacities of domestic dogs emphasizing the ones that considered the effect of associative learning upon these skills. In addition, evidence about differences in dogs' performance in following physical or social cues is summarized and two studies where both signals compete are presented here. The obtained results suggest that the training of a colour cue reverses the dogs' preference for the social one. These results are discussed in light of the findings that gave importance to the learning effect, concluding that the dogs fundamentally follow those cues that allowed them to obtain reinforcers in their previous learning history.

Incentive contrast in domestic dogs (Canis familiaris).

Dogs (Canis familiaris) trained to receive a preferred food (dry beef liver) from an experimenter learned to maintain a longer gaze on the experimenter than dogs receiving a less preferred food (dog pellets). Dogs downshifted from dry liver to pellets rejected food more frequently than nonshifted controls. Gaze duration also decreased in downshifted dogs below the level of a group always reinforced with pellets. In addition, downshifted dogs tended to move away from the experimenter, adopting a lying down posture. This phenomenon, called successive negative contrast, has been described in analogous experiments with a variety of mammalian species, but has failed to occur in similar experiments with nonmammalian vertebrates. Unlike similar previous observations, the present data were obtained in an environment involving interspecific communication.