International Journal of Comparative Psychology

This article describes the use of stickers to generate interest in comparative psychology. It is based on an earlier publication in which users can design their own official United States postage stamps (Abramson & Long, 2012). The company that developed the product no longer manufactures it, so we created a substitute using stickers that can be placed, for instance, on the bottom flap of an envelope. In addition to highlighting aspects of comparative psychology, such as individuals, apparatus, and movements, the stickers can also be used to feature other aspects of psychology. They can also be used as a fundraiser and recruitment tool. Developing the stickers is an excellent student-based project suitable for all courses, including the history of psychology. QR and/or bar codes can be added to link to student-developed resources. 

This study examines human and non-human animal communication from a linguistic–semiotic perspective to address the limitations of anthropocentric models that treat language and animal signaling as a strict dichotomy. Existing studies often emphasize human linguistic uniqueness without adequately accounting for semiotic continuities across species. To address this gap, the study conceptualizes communication as a semiotic continuum rather than a binary distinction. Using a qualitative comparative design, the research analyzes multimodal data from human communication and selected animal systems, including honeybee dances, dolphin echolocation, birdsong, and primate alarm calls. Data were examined through a coding framework based on Peircean semiotics and Hockett’s design features to ensure analytical rigor and comparability. The findings indicate that human communication is distinguished by symbolic abstraction, open-ended productivity, recursion, and metacommunication. However, animal communication systems also demonstrate structured, intentional, and adaptive properties shaped by ecological and social demands. Continuities across species include proto-syntactic patterning in primate calls, cultural transmission in birdsong, and multimodal coordination in dolphins and bees. Despite these shared features, animal systems generally lack the generativity and metalinguistic reflexivity characteristic of human language. The study concludes that communication should be understood as a graded semiotic continuum, with human language representing the most elaborated form of meaning-making rather than an isolated system. This reconceptualization contributes to theories of language evolution and broadens semiotic inquiry by situating human communication within a wider ecology of signs. 

Siamangs (Symphalangus syndactylus), one of the few singing apes, vocalize loudly, often while they move. We hypothesize that movement and vocalization coordinate, possibly due to vigorous thorax-loading movements such as brachiation affecting vocal-respiratory dynamics. To assess this vocal-motor coordination we recorded more than a hundred stereotypical vocalizations combined with movement from two captive Siamang (isolated from 7 hours of singing). We observed that stereotypical calls coincided with a movement display and were performed by juvenile individuals during solo singing (which allowed for isolation of the calls). Investigating these vocal-motor events, we found that body acceleration estimated using computer vision was statistically associated with the nearest peak in the amplitude envelope of the call, and that body acceleration timeseries contained mutual information about the amplitude envelope timeseries during these events. By confirming via quantitative methods that singing and movement are coordinated, the current report invites further mechanistic investigation on vocal-locomotor coupling in siamang. 

Creativity research suggests that creative output can be influenced by extrinsic rewards. Through reinforcement, individual killer whales were trained to produce varied behaviors to a particular cue. The purpose of this study was to opportunistically assess whether or not testing protocols, which varied in reinforcement schedules across four killer whales, influenced the outcomes of four measured constructs of creativity (Fluency, Flexibility, Elaboration, Originality) during the innovate task while under stimulus control. Of the four killer whales, one animal experienced a continuous reinforcement schedule for all test sessions, one experienced a variable reinforcement schedule for all test sessions, and two experienced two types of reinforcement schedules (6 sessions of continuous reinforcement followed by 6 sessions of variable reinforcement). Results suggested that both individuality and reinforcement schedule may have influenced the expression of selected behaviors for some constructs. A prospective study on the influence of reinforcement schedule during testing with larger samples would facilitate a clearer understanding of the mechanisms that influence the different outcomes of creative behavioral expressions. More importantly though, participation in cognitive tasks enables animals to engage in flexible thinking while actively controlling their behavioral choices during interactions with humans, thereby augmenting animal well-being in a positive way. 

This theoretical and integrative neuroscience review examines the neural mechanisms underlying nonverbal communication, focusing on how the human brain processes body language cues, including posture, gestures, and facial expressions. Drawing from recent advancements in affective neuroscience, social cognition, and neuroimaging research, the article synthesizes findings across multiple disciplines to explain the functional roles of key brain structures, including the amygdala, prefrontal cortex, superior temporal sulcus, and mirror neuron systems, in decoding nonverbal signals. The review highlights how these structures collaborate to interpret social and emotional meaning embedded in nonverbal behavior, with implications for understanding social disorders and improving interpersonal communication. Particular emphasis is placed on studies from the past 10 years to ensure contemporary relevance. This review also addresses theoretical frameworks such as Embodied Simulation Theory to contextualize empirical findings within broader models of brain evolution and communication. By integrating cognitive, affective, and evolutionary perspectives, this paper aims to clarify the neural architecture that supports nonverbal social interaction. 

Psychosocial stress exposure during sensitive periods of development affects brain circuits involved in emotional regulation and contributes to the emergence of mood disorders as well as alterations in peripheral organ function. Most experimental studies have used post-weaning social isolation (SI) spanning the entire adolescent period to model early-life adversity. However, adolescence comprises heterogeneous developmental phases, marked by region-specific brain maturation and dynamic endocrine changes. Exposure to adverse environments during these distinct windows may therefore produce divergent behavioral and physiological outcomes. Yet, the role of developmental timing in determining the susceptibility of peripheral organs to stress remains poorly understood. Here, we assessed the immediate effects of a 10-day acute SI protocol, starting in mid-adolescence (postnatal day [PND] 35) in male NMRI mice, a stage where adolescence overlaps with puberty. We evaluated a on broad range of behavioral outcomes and on peripheral physiology, including renal and hepatic function through blood biochemistry analysis, in order to determine how stress exposure during a specific developmental window impacts both central and peripheral physiological processes.  Our results revealed that mice housed in SI exhibited a hyperactivity phenotype and increased anxiety-like and depressive-like states, while cognitive function remained intact. At the peripheral level, SI induced early signs of hepatic stress under basal conditions, reflected by elevated plasma alanine aminotransferase (ALT) levels, without evidence of renal injury. Together, these results highlight the critical importance of developmental timing in shaping stress-related behavioral and peripheral outcomes and suggest that mid-adolescence constitutes a window of heightened vulnerability.

Genetic studies of reflex epilepsy are conducted primarily on rodent strains in which seizures are triggered by audiogenic stimuli. The genetic aspects of somatosensory epilepsy induced by tactile stimuli remain unclear. Identifying genes that influence the development of seizures evoked by tactile stimuli is important for understanding the underlying mechanisms of somatosensory epilepsy, as well as for its prevention and treatment. This article summarizes previously published results from long-term population and laboratory studies, confirming the assumption of other authors that seizures induced by tactile stimuli are an element of antipredatory behavior that allows the preservation of genes predisposing to somatosensory epilepsy in natural populations. The genetic predisposition of water voles to handling-induced seizures has been shown to be associated with a coat color polymorphism controlled by the agouti locus. Thus, the water vole may become a promising object for genetic studies of somatosensory reflex epilepsy and understanding the evolutionary origins of this disease. 

Stimulus generalization is a phenomenon in which an animal that is trained to respond to one specific stimulus exhibits a similar but not an identical response when presented with a new similar stimulus. It has been widely demonstrated across a variety of vertebrates. This study investigated stimulus generalization in Western painted turtles (Chrysemys picta), a phenomenon previously rarely studied in turtles. Three turtles were initially trained to criterion in an automated Skinner box on a discrimination task between vertical and horizontal lines. Reward was beef baby food, pumped from a syringe pump. Analysis of the criterion days showed a significant difference between the latencies to the reinforced and unreinforced stimuli, indicating successful discrimination. Following this training, the turtles were tested for stimulus generalization using lines of seven different orientations (from 0 degrees to 90 degrees in 15 degree increments), involving 20 days of testing. The results revealed that response latency varied with the line’s orientation. The fastest latencies were observed for the previously reinforced stimulus and the slowest for the previously unreinforced stimulus, with intermediate response times for the novel intermediate stimuli. This graded pattern formed a generalization gradient, which was best fit by an exponential function (R2 = 0.96). These findings suggest that painted turtles are capable not only of discriminating visual stimuli but also of exhibiting typical stimulus generalization. 

Conditioned inhibition (CI) refers to the learned property of a stimulus to predict the absence of an unconditioned stimulus (US). While excitatory forms of conditioning, like alpha conditioning, appear early in metazoan evolution, evidence of true CI in invertebrates remains scant. In the present study, we employed a negative contingency CI training design with an approach/withdrawal test to identify excitatory components involved in CI-like protocols in Caenorhabditis elegans. By using a joint-presentation procedure and alternating stimulus application sites across blocks, we minimised non-associative sensory effects. A control group was added to further consider context-dependent effects. Our results point to learning effects being consistent with excitatory (alpha) conditioning, as trained behavior was facilitated but did not depend on the conditioned stimulus. This underlines the widespread significance of alpha conditioning in invertebrate learning and its contribution to CI-like processes. 

Many animal behaviors are executed with appropriate form, direction, and intensity in accordance with an individual’s physiological state and its history of interactions with the environment. Although taxis has long provided a useful framework for describing stimulus-guided orientation, contemporary work has shown that such responses are mechanistically diverse and can involve more than simple automatic approach or avoidance. Here, we examined whether phototaxis in the acoel flatworm (Praesagittifera naikaiensis) undergoes experience-dependent modification. We conducted three experiments. First, we tested whether prior light exposure for 1 to 5 days attenuates phototaxis. A prolonged light exposure weakened phototactic attraction. This attenuation, however, could reflect general debilitation caused by light exposure. We therefore assessed in Experiment 2 whether five days of light exposure reduces spontaneous locomotor activity. No such reduction was detected. In Experiment 3, we placed P. naikaiensis on a platform containing a continuously illuminated region and a shaded region for five days, and asked whether prolonged exposure would induce spontaneous light avoidance. The worms were attracted to light for approximately the first 24 hours, after which they tended to avoid light and moved into the shaded region. These results indicate that phototaxis in P. naikaiensis is adaptively tuned to the individual’s history of light exposure.