The canine sand maze: an appetitive spatial memory paradigm sensitive to age-related change in dogs

Aged dogs exhibit a spectrum of cognitive abilities including a syndrome similar to Alzheimer's disease. A major impediment to research so far has been the lack of a quick and accurate test of visuospatial memory appropriate for community-based animals. We therefore report on the development and validation of the Canine Sand Maze. A 4.5-m-diameter circular pool was filled with a sand and powdered food reward mix to a depth of 10 cm. Dogs were given 4 habituation and 16 learning trials which alternated a food reward being half (control trials) or fully-buried (acquisition trials) in a fixed location. After a 90-min break, a probe trial was conducted. Cognitively normal, aged (> 8 years, n = 11) and young (1-4 years, n = 11), breed-matched dogs were compared. After correction for differences in control trials, average probe times were 2.97 and 10.81 s for young and aged dogs, respectively. In the probe trial, both groups spent significantly more time in the target quadrant but there was a trend for young dogs to cross a 1 m(2) annulus zone around the buried reward more frequently (2.6 times) than aged dogs (1.5 times). Test-retest reliability in a subset of young dogs (n = 5) was high. On the basis of these findings, the Canine Sand Maze is presented as a quick, sensitive and nonaversive tool for assessing spatial learning and reference memory in dogs.     

Modeling the effect of reward amount on probability discounting

The present study with college students examined the effect of amount on the discounting of probabilistic monetary rewards. A hyperboloid function accurately described the discounting of hypothetical rewards ranging in amount from $20 to $10,000,000. The degree of discounting increased continuously with amount of probabilistic reward. This effect of amount was not due to changes in the rate parameter of the discounting function, but rather was due to increases in the exponent. These results stand in contrast to those observed with the discounting of delayed monetary rewards, in which the degree of discounting decreases with reward amount due to amount-dependent decreases in the rate parameter. Taken together, this pattern of results suggests that delay and probability discounting reflect different underlying mechanisms. That is, the fact that the exponent in the delay discounting function is independent of amount is consistent with a psychophysical scaling interpretation, whereas the finding that the exponent of the probability-discounting function is amount-dependent is inconsistent with such an interpretation. Instead, the present results are consistent with the idea that the probability-discounting function is itself the product of a value function and a weighting function. This idea was first suggested by Kahneman and Tversky (1979), although their prospect theory does not predict amount effects like those observed. The effect of amount on probability discounting was parsimoniously incorporated into our hyperboloid discounting function by assuming that the exponent was proportional to the amount raised to a power. The amount-dependent exponent of the probability-discounting function may be viewed as reflecting the effect of amount on the weighting of the probability with which the reward will be received.     

Concerning the resilience of Galen Strawson’s Basic Argument

Against its prominent compatiblist and libertarian opponents, I defend Galen Strawson’s Basic Argument for the impossibility of moral responsibility. Against John Martin Fischer, I argue that the Basic Argument does not rely on the premise that an agent can be responsible for an action only if he is responsible for every factor contributing to that action. Against Alfred Mele and Randolph Clarke, I argue that it is absurd to believe that an agent can be responsible for an action when no factor contributing to that action is up to that agent. Against Derk Pereboom and Clarke, I argue that the versions of agent-causal libertarianism they claim can immunize the agent to the Basic Argument actually fail to do so. Against Robert Kane, I argue that the Basic Argument does not rely on the premise that simply the presence of indeterministic factors in the process of bringing an action about is itself what rules out the agent’s chance for being responsible for that action.     

Item and order information in semantic memory: students’ retention of the “CU fight song” lyrics

University of Colorado (CU) students were tested on memory for the “CU Fight Song” in order to examine serial position effects in semantic memory while controlling for familiarity across positions. In Experiment 1, students reconstructed the order of the nine lines of the song. Students with previous exposure to the song performed better and showed a more bowed serial position function than did students with no knowledge of the song. Experiment 2 added a task assessing memory of item information. One word was removed and replaced with a blank in each line, and an alternative word was offered as an option, along with the correct word. Students selected the word that fit into each blank and then reconstructed the order of the lines. There was a bow-shaped curve for order reconstruction, but not for item selection, which implies that the serial position function in semantic memory stems from order, rather than item, information.     

The effects of proactive interference (PI) and release from PI on judgments of learning

In three experiments, we investigated metacognitive monitoring in a variant of an A–B A–C learning paradigm in which the repetition of cues, but not targets, led to increasing proactive interference (PI) across trials. Judgments of learning (JOLs) correctly predicted decreases across trials in this paradigm but incorrectly continued to predict decreases on a final release trial in which new cues were introduced and performance consequently increased. Experience with the paradigm did not ameliorate this metacognitive failure (Experiment 3). In addition, JOLs decreased equally for pairs with repeated and with novel cue terms, even though recall of the latter group of items did not decrease across trials (Experiment 2). These results suggest that metacognizers’ naïve theories of remembering and forgetting include a role for global, but not cue-specific, interference.     

Reading aloud: New evidence for contextual control over the breadth of lexical activation

Computational accounts of reading aloud largely ignore context when stipulating how processing unfolds. One exception to this state of affairs proposes adjusting the breadth of lexical knowledge in such models in response to differing contexts. Three experiments and corresponding simulations, using Coltheart, Rastle, Perry, Langdon, and Ziegler’s (2001) dual-route cascaded model, are reported. This work investigates a determinant of when a pseudohomophone such as brane is affected by the frequency of the word from which it is derived (e.g., the base word frequency of brain) by examining performance under conditions where it is read aloud faster than a nonword control such as frane. Reynolds and Besner’s (2005a) lexical breadth account makes the novel prediction that when a pseudohomophone advantage is seen, there will also be a base word frequency effect, provided exception words are also present. This prediction was confirmed. Five other accounts of this pattern of results are considered and found wanting. It is concluded that the lexical breadth account provides the most parsimonious account to date of these and related findings.     

The Delinquency Outcomes of Boys with ADHD with and Without Comorbidity

This study examined the association between childhood ADHD and juvenile delinquency by examining data from the Pittsburgh ADHD Longitudinal Study (PALS), a follow-up study of individuals diagnosed with ADHD in childhood (ages 5–12) and recontacted in adolescence and young adulthood for yearly follow-up (age at first follow-up interview M = 17.26, SD = 3.17). Participants were 288 males with childhood ADHD and 209 demographically similar males without ADHD who were recruited into the follow-up study. Delinquency information gathered yearly during the second through eighth follow-up provided a comprehensive history of juvenile delinquency for all participants. Four childhood diagnostic groups [ADHD-only (N = 47), ADHD + ODD (N = 135), ADHD + CD (N = 106), and comparison (N = 209)] were used to examine group differences on delinquency outcomes. Analyses were conducted across three dimensions of delinquency (i.e., severity, age of initiation, and variety). Individuals with childhood ADHD + CD displayed significantly worse delinquency outcomes than the other three groups, across almost all indices of offending. When compared to comparison participants, boys with ADHD-only and ADHD + ODD in childhood displayed earlier ages of delinquency initiation, a greater variety of offending, and higher prevalence of severe delinquency. These findings suggest that although childhood ADHD + CD creates the greatest risk for delinquency, boys with ADHD-only and ADHD + ODD also appear at a higher risk for later offending. The patterns of offending that emerged from the PALS are discussed in the context of the relationship between ADHD, comorbidity, and delinquency.