Damian Scarf

Pigeons on Par with Primates in Numerical Competence

Pigeons’ ability to use abstract numerical rules appears identical to that of monkeys. Although many animals are able to discriminate stimuli differing in numerosity, only primates are thought to share our ability to employ abstract numerical rules. Here, we show that this ability is present in pigeons and that their performance is indistinguishable from that displayed by monkeys.

To have and to hold: Episodic memory in 3- and 4-year-old children

Episodic memory endows us with the ability to reflect on our past and plan for our future. Most theorists argue that episodic memory emerges during the preschool period and that its emergence might herald the end of childhood amnesia. Here, we show that both 3- and 4-year-old children form episodic memories, but that 3-year-old children fail to retain those memories following a delay (Experiments 1 and 2). In contrast, 4-year-old children retained episodic memories over delays of 24 hr (Experiment 1) and 1 week (Experiment 3). This marked change in the retention of episodic memories between 3 and 4 years of age suggests that it is our ability to retain, rather than to form, an episodic memory that limits our ability to recall episodes from early childhood.

Social Evaluation or Simple Association? Simple Associations May Explain Moral Reasoning in Infants

Are we born amoral or do we come into this world with a rudimentary moral compass? Hamlin and colleagues argue that at least one component of our moral system, the ability to evaluate other individuals as good or bad, is present from an early age. In their study, 6- and 10-month-old infants watched two social interactions - in one, infants observed the helper assist the climber achieve the goal of ascending a hill, while in the other, infants observed the hinderer prevent the climber from ascending the hill. When given a choice, the vast majority of infants picked the helper over the hinderer, suggesting that infants evaluated the helper as good and the hinderer as bad. Hamlin and colleagues concluded that the ability to evaluate individuals based on social interaction is innate. Here, we provide evidence that their findings reflect simple associations rather than social evaluations.

Representation of serial order: a comparative analysis of humans, monkeys, and pigeons.

In a serial-order task, subjects are trained to respond to five stimuli in a specific order, (e.g., A-->B-->C-->D-->E) to obtain a reward. Once the serial-order task is learned, a pairwise test is administered in which all ten pairwise combinations of the five stimuli are presented to the subject. Humans and monkeys respond at high levels on all pairwise items, that is, they respond to the items in the pair in the order in which they appear in the original sequence. Given pair BD, for example, humans and monkeys first respond to item B and then item D. Examination of the latencies reveals that humans and monkeys show a first-item effect, a missing-item effect, and a symbolic-distance effect, all in line with the view that they form a representation of the order of the five items and use that representation to guide their behaviour during the pairwise test. In contrast, pigeons perform poorly on the pairwise test, and show no first-item, missing-item, or symbolic-distance effects, suggesting that although pigeons can learn to respond to five items in a specific order, they do not form a representation of the sequential order of those items. We discuss the extent to which the difference in performance between birds and primates on the serial-order task reflects a difference in cognitive abilities, or whether the difference can be attributed to noncognitive factors.

Mental time travel for self and other in three- and four-year-old children

Humans possess the unique ability to mentally travel backward in time to re-experience past events (i.e., episodic memory) and forward in time to pre-experience future events (i.e., episodic foresight). Although originally viewed as different cognitive skills, they are now both viewed as components of the episodic memory system. Recently, it has been suggested that the episodic system may allow us to not only pre-experience and predict our own future but also that of another person. In the current study, we investigate this possibility by examining the ability of three- and four-year-old children to plan for their own future and for that of another person. We found that both three- and four-year-old children performed equally, when planning for their own future or when planning for the experimenters future. These data are consistent with the finding that planning for someone elses future recruits the same neural structures that are used when planning for ones own future.

Brain cells in the avian 'prefrontal cortex' code for features of slot-machine-like gambling.

Slot machines are the most common and addictive form of gambling. In the current study, we recorded from single neurons in the ‘prefrontal cortex’ of pigeons while they played a slot-machine-like task. We identified four categories of neurons that coded for different aspects of our slot-machine-like task. Reward-Proximity neurons showed a linear increase in activity as the opportunity for a reward drew near. I-Won neurons fired only when the fourth stimulus of a winning (four-of-a-kind) combination was displayed. I-Lost neurons changed their firing rate at the presentation of the first nonidentical stimulus, that is, when it was apparent that no reward was forthcoming. Finally, Near-Miss neurons also changed their activity the moment it was recognized that a reward was no longer available, but more importantly, the activity level was related to whether the trial contained one, two, or three identical stimuli prior to the display of the nonidentical stimulus. These findings not only add to recent neurophysiological research employing simulated gambling paradigms, but also add to research addressing the functional correspondence between the avian NCL and primate PFC.

Representation of serial order in pigeons (Columba livia).

In Experiment 1, 2 groups of pigeons were trained to respond to either a 4-item (A→B→C→D) or 5-item (A→B→C→D→E) list. After learning their respective list, half of the subjects were trained on a positive pair with reinforcement provided when pairs were responded to in the order true to that of the original sequence (4-item: B→C; 5-item: B→D). The remaining subjects were trained on a negative pair with reinforcement provided for responding to the pairs in the order opposite to that learned in the original sequence (4-item: C→B; 5-item: D→B). Subjects in the positive pair condition learned their respective pair faster than did subjects in the negative pair condition. In Experiment 2, after reaching criterion on a 4-item list, subjects received 16 BC probe trials spread across 4 sessions of training. Subjects performed significantly above chance on the probe trials. The performance of our subjects in Experiments 1 and 2 demonstrates that, similar to monkeys, pigeons form a representation of the lists that they learn.

A spoon full of studies helps the comparison go down: a comparative analysis of Tulving’s spoon test

Mental time travel refers to the ability to cast one’s mind back in time to re-experience a past event and forward in time to pre-experience events that may occur in the future. Tulving (2005), an authority on mental time travel, holds that this ability is unique to humans. Anticipating that comparative psychologists would challenge this claim, Tulving (2005) proposed his spoon test, a test specifically designed to assess whether non-human animals are capable of mental time travel. A number of studies have now employed the spoon test to assess mental time travel in non-human animals. Here, we review the evidence for mental time travel in primates. To provide a benchmark, we also review studies that have employed the spoon test with preschool children. The review demonstrates that if we compare the performance of great apes to that of preschool children, and hold them to the same criteria, the data suggest mental travel is present but not ubiquitous in great apes.

Drawing a close to the use of human figure drawings as a projective measure of intelligence

The practice of using childrens human figure drawings (HFDs) to assess their intellectual ability is pervasive among psychologists and therapists in many countries. Since the first systematic scoring system for HFDs was published in 1926, their continued popularity has led to the development of several revised versions of the test. Most recently, the Draw-A-Person Intellectual Ability Test for children, adolescents, and adults (DAP:IQ) was published. It is the most up-to-date form of HFD test designed to assess intellectual functioning across a wide age range. In the present study, we assessed the validity of the DAP:IQ as a screening measure of intelligence in both children and adults. In Experiment 1, 100 4- to 5-year-old children completed the DAP:IQ and the Wechsler Preschool and Primary Scale of Intelligence-Third Edition. In Experiment 2, 100 adults completed the DAP:IQ and the Wechsler Abbreviated Scale of Intelligence. In both experiments, we found only weak to modest correlations between scores on the DAP:IQ and the Wechsler tests. Furthermore, when we compared individuals scores on the two tests, the DAP:IQ yielded high false positive and false negative rates when screening for borderline and superior intellectual functioning. Based on these findings, and based on the lack of validity of previous HFD tests, we conclude that practitioners should not rely on HFD tests as a projective measure of intelligence.

Knowledge of the ordinal position of list items in pigeons.

Ordinal knowledge is a fundamental aspect of advanced cognition. It is self-evident that humans represent ordinal knowledge, and over the past 20 years it has become clear that nonhuman primates share this ability. In contrast, evidence that nonprimate species represent ordinal knowledge is missing from the comparative literature. To address this issue, in the present experiment we trained pigeons on three 4-item lists and then tested them with derived lists in which, relative to the training lists, the ordinal position of the items was either maintained or changed. Similar to the findings with human and nonhuman primates, our pigeons performed markedly better on the maintained lists compared to the changed lists, and displayed errors consistent with the view that they used their knowledge of ordinal position to guide responding on the derived lists. These findings demonstrate that the ability to acquire ordinal knowledge is not unique to the primate lineage. (PsycINFO Database Record (c) 2011 APA, all rights reserved).