Individual organisms face trade-offs when dealing with predation—more time spent avoiding predators often results in less time allocated to energy acquisition and reproductive-related activities. Individuals that optimize this trade-off and respond appropriately to current risk levels in their environment should be at an advantage. What is less clear is whether this tradeoff changes when individuals are repeatedly exposed to a predation threat. There may be advantages to responding consistently to every signal of threat, but it might also be advantageous to modulate individual behavior. Moreover, it is unclear how evolutionary history of a population might affect such individual responses. Our study was designed to address two questions: (1) how do B. rhabdophora respond to repeated exposures of a predation cue; and (2) do repeated responses differ based on evolutionary history? To answer these questions, we used a predation cue stimulus to repeatedly expose B. rhabdophora individuals from both high- and low-predation populations. We measured the change in total distance traveled in a 15-minute trial before and after each cue exposure, and then compared the proportional change in response to the first cue to that of each successive cue (repeated four times) to see if a decrease in response occurred. We found that fish responded consistently to each cue exposure. Both populations showed similar decreases in activity in response to each exposure and did not return to normal baseline activity until the cue was removed from the test tank. That both high- and low-predation populations respond consistently to repeated cues of predation with no reinforcement prompts questions as to the potential importance of the relative length of risk and safe periods in affecting response variation. It also provides a starting point in understanding how recent risk exposure and the evolutionary history of risk in a population both interact to influence individual response to threats over time.

A variação comportamental coloca o organismo em contato com diferentes contingências, possibilitando o fortalecimento de comportamentos incialmente pouco prováveis. Entretanto, a literatura experimental sobre a aprendizagem de comportamentos de baixa probabilidade inicial influenciada por reforçamento da variação tem encontrado diferenças marcantes entre desempenhos de humanos e não humanos. Dentre as variáveis sugeridas como responsáveis por essas diferenças está o controle verbal pelas instruções fornecidas aos humanos que pode interagir com as contingências em vigor. Foram realizados dois experimentos visando o teste dessa variável. No Exp.1 foi analisado o efeito de instruções para descobrir o que deveria ser feito (ID), comparado ao de instruções mínimas (IM). A tarefa consistiu em sequências de quatro pressões em duas teclas (Q e P) de um computador, sendo a ordem dessas teclas na sequência o que diferenciou as 16 sequências possíveis. Após uma linha de base em que os participantes produziam reforços independente da configuração das sequências emitidas, todos foram expostos a duas contingências concorrentes: FR1 contingente à sequência menos emitida na fase anterior (sequência alvo - SA) ou reforçamento de sequências que variassem entre si dentre as 15 restantes. Dois grupos de estudantes universitários participaram desse experimento. Os participantes de um dos grupos (n=14) foram submetidos à instrução ID e os participantes do outro grupo (n=14) foram submetidos à instrução IM. Cada grupo foi subdividido em dois em função do padrão de variação apresentado na linha de base (alto ou baixo). Nenhuma diferença significante foi encontrada entre os grupos como função das instruções, mas o nível de variabilidade apresentado pelos participantes em linha de base se mostrou um preditor consistente da emissão de SAs. Hipotetizou-se que os reforços dispensados em FR 1 na linha de base poderiam ter fortalecido padrões que se mantiveram na fase seguinte, interferindo no eventual efeito das instruções. Para avaliar essa hipótese, foi realizado um segundo experimento, similar ao anterior, no qual foi excluída a fase de linha de base. Dezoito novos estudantes serviram como participantes sendo divididos em grupos ID e IM. Os resultados mostraram não haver diferenças significantes entre os grupos. Sugere-se que, nas condições testadas, a apresentação de vii instruções que especificam uma tarefa de descobrir a regra (ID) não constitui variável significativa na determinação do desempenho dos participantes humanos. Portanto, essa interpretação não parece ser adequada para justificar as diferenças entre humanos e não humanos submetidos a procedimentos aparentemente similares. São apresentadas sugestões de experimentos que poderão contribuir para o melhor entendimento do papel das variáveis envolvidas nessa diferença entre espécies / The behavioral variation puts the organism in contact with different contingencies, therefore strengthening unlikely behaviors. The experimental literature about learning of behaviors of low initial probability influenced by reinforcement of variation, however, has found striking differences between performances of humans and nonhumans. One of the variables suggested as responsible for these differences is the control by verbal instructions given to humans that can interact with the contingencies in place. Two experiments were conducted in order to test this variable. The Exp.1 analyzed the effect of instructions to \"find out what should be done\" (ID), compared to minimal instructions (IM). The task consisted of four presses sequences on two keyboard keys (P and Q), the order of these key presses in the sequence is what differentiated the 16 possible sequences. After a baseline in which the participants produced reinforcement regardless of the configuration of the sequences emitted, all of them were exposed to two competing contingencies: FR1 contingent to the least emitted sequence in the previous phase (target sequence - TS) or reinforcement for variation among the 15 remaining sequences. Two groups of students participated in this experiment. Participants in one group (n = 14) received instruction ID and participants in the other group (n=14) received instruction IM. Each group was subdivided into other two groups depending on the variation pattern shown at baseline (high or low). No significant differences were found between the groups as a function of the instructions, but the level of variability presented by participants at baseline proved to be a consistent predictor of emitting TSs. It was hypothesized that the reinforcements dispensed in FR 1 over baseline patterns could have strengthened the patterns which remained in the next phase, possibly interfering on the effect of the instructions. To assess this hypothesis, a second experiment, similar to the previous one, was performed in which the baseline phase was excluded. Eighteen new students served as participants and were divided into groups and IM and ID. The results showed no significant differences between groups. It is suggested that, under the conditions tested, the presentation of instructions that specify a task of \"discovering the rule\" (ID) is not a significant variable in determining the performance of human participants. Therefore, this interpretation does not seem adequate to explain the differences between human and nonhuman exposed to apparently similar procedures. Experiments that could ix contribute to a better understanding of the role of the variables involved in this difference between species were suggested

A variação comportamental coloca o organismo em contato com diferentes contingências, possibilitando o fortalecimento de comportamentos incialmente pouco prováveis. Entretanto, a literatura experimental sobre a aprendizagem de comportamentos de baixa probabilidade inicial influenciada por reforçamento da variação tem encontrado diferenças marcantes entre desempenhos de humanos e não humanos. Dentre as variáveis sugeridas como responsáveis por essas diferenças está o controle verbal pelas instruções fornecidas aos humanos que pode interagir com as contingências em vigor. Foram realizados dois experimentos visando o teste dessa variável. No Exp.1 foi analisado o efeito de instruções para descobrir o que deveria ser feito (ID), comparado ao de instruções mínimas (IM). A tarefa consistiu em sequências de quatro pressões em duas teclas (Q e P) de um computador, sendo a ordem dessas teclas na sequência o que diferenciou as 16 sequências possíveis. Após uma linha de base em que os participantes produziam reforços independente da configuração das sequências emitidas, todos foram expostos a duas contingências concorrentes: FR1 contingente à sequência menos emitida na fase anterior (sequência alvo - SA) ou reforçamento de sequências que variassem entre si dentre as 15 restantes. Dois grupos de estudantes universitários participaram desse experimento. Os participantes de um dos grupos (n=14) foram submetidos à instrução ID e os participantes do outro grupo (n=14) foram submetidos à instrução IM. Cada grupo foi subdividido em dois em função do padrão de variação apresentado na linha de base (alto ou baixo). Nenhuma diferença significante foi encontrada entre os grupos como função das instruções, mas o nível de variabilidade apresentado pelos participantes em linha de base se mostrou um preditor consistente da emissão de SAs. Hipotetizou-se que os reforços dispensados em FR 1 na linha de base poderiam ter fortalecido padrões que se mantiveram na fase seguinte, interferindo no eventual efeito das instruções. Para avaliar essa hipótese, foi realizado um segundo experimento, similar ao anterior, no qual foi excluída a fase de linha de base. Dezoito novos estudantes serviram como participantes sendo divididos em grupos ID e IM. Os resultados mostraram não haver diferenças significantes entre os grupos. Sugere-se que, nas condições testadas, a apresentação de vii instruções que especificam uma tarefa de descobrir a regra (ID) não constitui variável significativa na determinação do desempenho dos participantes humanos. Portanto, essa interpretação não parece ser adequada para justificar as diferenças entre humanos e não humanos submetidos a procedimentos aparentemente similares. São apresentadas sugestões de experimentos que poderão contribuir para o melhor entendimento do papel das variáveis envolvidas nessa diferença entre espécies / The behavioral variation puts the organism in contact with different contingencies, therefore strengthening unlikely behaviors. The experimental literature about learning of behaviors of low initial probability influenced by reinforcement of variation, however, has found striking differences between performances of humans and nonhumans. One of the variables suggested as responsible for these differences is the control by verbal instructions given to humans that can interact with the contingencies in place. Two experiments were conducted in order to test this variable. The Exp.1 analyzed the effect of instructions to \"find out what should be done\" (ID), compared to minimal instructions (IM). The task consisted of four presses sequences on two keyboard keys (P and Q), the order of these key presses in the sequence is what differentiated the 16 possible sequences. After a baseline in which the participants produced reinforcement regardless of the configuration of the sequences emitted, all of them were exposed to two competing contingencies: FR1 contingent to the least emitted sequence in the previous phase (target sequence - TS) or reinforcement for variation among the 15 remaining sequences. Two groups of students participated in this experiment. Participants in one group (n = 14) received instruction ID and participants in the other group (n=14) received instruction IM. Each group was subdivided into other two groups depending on the variation pattern shown at baseline (high or low). No significant differences were found between the groups as a function of the instructions, but the level of variability presented by participants at baseline proved to be a consistent predictor of emitting TSs. It was hypothesized that the reinforcements dispensed in FR 1 over baseline patterns could have strengthened the patterns which remained in the next phase, possibly interfering on the effect of the instructions. To assess this hypothesis, a second experiment, similar to the previous one, was performed in which the baseline phase was excluded. Eighteen new students served as participants and were divided into groups and IM and ID. The results showed no significant differences between groups. It is suggested that, under the conditions tested, the presentation of instructions that specify a task of \"discovering the rule\" (ID) is not a significant variable in determining the performance of human participants. Therefore, this interpretation does not seem adequate to explain the differences between human and nonhuman exposed to apparently similar procedures. Experiments that could ix contribute to a better understanding of the role of the variables involved in this difference between species were suggested

Den europeiska blankålen (Anguilla anguilla) har genomgått en stor populationsminskning de senaste decennierna på grund av antropogena strukturer i form av vattenkraftverk som orsakar fragmentering. Vid vattenkraftverks intagskanaler finns intagsgaller installerade för att förhindra drivgods från att skada turbinerna. Forskning har utvecklat lösningar i form av anpassade galler, med låg lutning, som leder fisken till en flyktöppning vid sidan av kraftverket. Det har observerats att utformningen av gallret påverkar fiskars beteenden och beteendeobservationer kan därför ge viktig kunskap om hur väl åtgärder funkar och vilka förbättringar som krävs. Syftet med denna studie var att undersöka beteenderespons och passageframgång för europeisk blankål (Anguilla anguilla) vid tre olika typer av låglutande ß-galler med 30 mm spaltvidd. Man ville också undersöka om det finns någon koppling mellan ålarnas beteenderespons och gallrens vägledande funktion.  Experimentet utfördes vid Vattenfalls Research and Development laboratorium i Älvkarleby. En artificiell miljö i form av en ränna användes för att simulera ett turbinintag. Här testades blankålars (n=69) beteende och passage av tre olika typer av ß-galler med (i) horisontella järn orienterade i linje med vattnets strömriktning (H0), (ii) vertikala järn orienterade i linje med vattnets strömriktning (V0) och (iii) vertikala järn med 60° vinkel mot strömmen (V60). Resultatet visar att det inte finns någon signifikant skillnad i ålarnas beteenderespons mellan de tre olika gallren. Däremot såg man att det fanns en koppling mellan ålarnas beteenderespons och gallrens vägledande förmåga. De ålar som vägleddes av gallren hade huvud som första fysiska kontakt med gallret. Vidare forskning på ålbeteenden vid intagsgaller är nödvändigt för att öka migrationsframgången hos europeisk ål. / The European silver eel (Anguilla anguilla) has undergone a large population decline in recent decades due to anthropogenic factors such as hydropower plant river fragmentation. At the intake channel of hydropower plants there are trash racks for preventing drifting obstacles to damage the turbines. Research has developed solutions such as angled bar racks, which guide fish to a bypass. The design of the racks has been observed has an effect on fish behavior and its therefore important to provide actions and improvements. The aim of this study was to investigate behavioral and passage success of the European silver eel (Anguilla anguilla) of three different types of low-sloping angled bar racks with 30 mm clear spacing and whether there is any connection between the behavioral response of the eels and the guiding function of the racks. The experiment took place at Vattenfall's Research and Development laboratory located in Älvkarleby. A flume resembling an intake channel was used. Here (n=69) eels were tested on three different types of low-sloping angled bar racks: (i) horizontally bars oriented in line with the water current streamwise (H0), (ii) vertical bars oriented in line with the water current streamwise (V0) and (iii) vertical bars with a 60° angle to the current (V60). The result shows that there is no significant difference in the eels behavioral response between the three different racks. However, it was seen that there was a connection between the behavioral response of the eels and the guiding ability of the racks. Al eels that were guided by the racks, only had head as first physical contact with the rack. Further research on eel behaviors at intake racks is necessary to increase the migration success of European eel.